v2.2.3

* switch to using Context internally

* add context import

* Add smoke test to make sure enabling GSN support works

* Update test/GSN/ERC721GSNRecipientMock.test.js

Co-Authored-By: Francisco Giordano <frangio.1@gmail.com>

* Upgrade truffle

* add missing awaits

* Revert "Upgrade truffle"

This reverts commit f9b0ba9019.

.circleci/config.yml

@@ -0,0 +1,82 @@
+version: 2
+# 2.1 does not yet support local run
+# unless with workaround. For simplicity just use it.
+# https://github.com/CircleCI-Public/circleci-cli/issues/79
+
+aliases:
+  - &defaults
+    docker:
+      - image: circleci/node:8
+
+  - &npm_install_if_necessary
+    run:
+      name: Install npm dependencies
+      command: |
+        if [ ! -d node_modules ]; then
+          npm ci
+        fi
+
+  - &cache_key_node_modules
+    key: v1-node_modules-{{ checksum "package-lock.json" }}
+
+jobs:
+  dependencies:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - save_cache:
+          paths:
+            - node_modules
+          <<: *cache_key_node_modules
+
+  lint:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - run:
+          name: Linter
+          command: npm run lint
+  test:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - run:
+          name: Unit tests
+          command: npm run test
+  coverage:
+    docker:
+      - image: circleci/node:8
+    steps:
+      - checkout
+      - restore_cache:
+          <<: *cache_key_node_modules
+      - *npm_install_if_necessary
+      - run:
+          name: Unit tests with coverage report
+          command: npm run coverage
+
+      # TODO(xinbenlv, #1839): run SOLC_NIGHTLY to be run but allow it to fail.
+
+workflows:
+  version: 2
+  everything:
+    jobs:
+      - dependencies
+      - lint:
+          requires:
+            - dependencies
+      - test:
+          requires:
+            - dependencies
+      - coverage:
+          requires:
+            - dependencies

.editorconfig

@@ -6,7 +6,12 @@ root = true
 [*]
 charset = utf-8
 end_of_line = lf
-indent_size = 2
 indent_style = space
 insert_final_newline = true
 trim_trailing_whitespace = true
+
+[*.sol]
+indent_size = 4
+
+[*.js]
+indent_size = 2

.gitignore

@@ -38,5 +38,7 @@ build/
 # truffle
 .node-xmlhttprequest-*
 
+.openzeppelin/.session
+
 # IntelliJ IDE
 .idea

.openzeppelin/kovan.json

@@ -0,0 +1,923 @@
+{
+  "contracts": {
+    "StandaloneERC721": {
+      "address": "0xb8cBf1CC110c42C15CEf3CA0982b812a82d99613",
+      "constructorCode": "60806040526139f3806100136000396000f3fe",
+      "bodyBytecodeHash": "33aac4411967c3463cdac9bb7d6d491c9bd9f8338aeb53d8ebe0cf054abb2508",
+      "localBytecodeHash": "16e6da0afa76f1d342939ec26b9213e99b8b707e52b930005971e9d752fdc54a",
+      "deployedBytecodeHash": "16e6da0afa76f1d342939ec26b9213e99b8b707e52b930005971e9d752fdc54a",
+      "types": {
+        "t_bool": {
+          "id": "t_bool",
+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
+          "id": "t_uint256",
+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_mapping<t_bool>": {
+          "id": "t_mapping<t_bool>",
+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        },
+        "t_address": {
+          "id": "t_address",
+          "kind": "elementary",
+          "label": "address"
+        },
+        "t_mapping<t_address>": {
+          "id": "t_mapping<t_address>",
+          "valueType": "t_address",
+          "label": "mapping(key => address)",
+          "kind": "mapping"
+        },
+        "t_struct<Counters.Counter>": {
+          "id": "t_struct<Counters.Counter>",
+          "kind": "struct",
+          "label": "Counters.Counter",
+          "members": [
+            {
+              "label": "_value",
+              "astId": 3662,
+              "type": "t_uint256",
+              "src": "1021:14:30"
+            }
+          ]
+        },
+        "t_mapping<t_struct<Counters.Counter>>": {
+          "id": "t_mapping<t_struct<Counters.Counter>>",
+          "valueType": "t_struct<Counters.Counter>",
+          "label": "mapping(key => Counters.Counter)",
+          "kind": "mapping"
+        },
+        "t_array:dyn<t_uint256>": {
+          "id": "t_array:dyn<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "dyn",
+          "kind": "array",
+          "label": "uint256[]"
+        },
+        "t_mapping<t_array:dyn<t_uint256>>": {
+          "id": "t_mapping<t_array:dyn<t_uint256>>",
+          "valueType": "t_array:dyn<t_uint256>",
+          "label": "mapping(key => uint256[])",
+          "kind": "mapping"
+        },
+        "t_mapping<t_uint256>": {
+          "id": "t_mapping<t_uint256>",
+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_string": {
+          "id": "t_string",
+          "kind": "elementary",
+          "label": "string"
+        },
+        "t_mapping<t_string>": {
+          "id": "t_mapping<t_string>",
+          "valueType": "t_string",
+          "label": "mapping(key => string)",
+          "kind": "mapping"
+        },
+        "t_struct<Roles.Role>": {
+          "id": "t_struct<Roles.Role>",
+          "kind": "struct",
+          "label": "Roles.Role",
+          "members": [
+            {
+              "label": "bearer",
+              "astId": 1222,
+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13536,
+          "type": "t_bool",
+          "src": "757:24:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13538,
+          "type": "t_bool",
+          "src": "876:25:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13594,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:154"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "_supportedInterfaces",
+          "astId": 5232,
+          "type": "t_mapping<t_bool>",
+          "src": "511:52:39"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "______gap",
+          "astId": 5276,
+          "type": "t_array:50<t_uint256>",
+          "src": "1244:29:39"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenOwner",
+          "astId": 11717,
+          "type": "t_mapping<t_address>",
+          "src": "886:48:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenApprovals",
+          "astId": 11721,
+          "type": "t_mapping<t_address>",
+          "src": "990:52:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_ownedTokensCount",
+          "astId": 11725,
+          "type": "t_mapping<t_struct<Counters.Counter>>",
+          "src": "1100:63:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_operatorApprovals",
+          "astId": 11731,
+          "type": "t_mapping<t_bool>",
+          "src": "1218:73:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "______gap",
+          "astId": 12258,
+          "type": "t_array:50<t_uint256>",
+          "src": "11985:29:136"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokens",
+          "astId": 12316,
+          "type": "t_mapping<t_array:dyn<t_uint256>>",
+          "src": "502:50:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokensIndex",
+          "astId": 12320,
+          "type": "t_mapping<t_uint256>",
+          "src": "622:53:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokens",
+          "astId": 12323,
+          "type": "t_array:dyn<t_uint256>",
+          "src": "736:28:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokensIndex",
+          "astId": 12327,
+          "type": "t_mapping<t_uint256>",
+          "src": "835:51:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "______gap",
+          "astId": 12656,
+          "type": "t_array:50<t_uint256>",
+          "src": "8858:29:138"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_name",
+          "astId": 12726,
+          "type": "t_string",
+          "src": "323:20:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_symbol",
+          "astId": 12728,
+          "type": "t_string",
+          "src": "370:22:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_tokenURIs",
+          "astId": 12732,
+          "type": "t_mapping<t_string>",
+          "src": "438:45:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "______gap",
+          "astId": 12861,
+          "type": "t_array:50<t_uint256>",
+          "src": "2891:29:141"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1455,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1555,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:10"
+        },
+        {
+          "contract": "ERC721MetadataMintable",
+          "path": "contracts/token/ERC721/ERC721MetadataMintable.sol",
+          "label": "______gap",
+          "astId": 12931,
+          "type": "t_array:50<t_uint256>",
+          "src": "1055:29:142"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1578,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1678,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5445,
+          "type": "t_bool",
+          "src": "406:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5526,
+          "type": "t_array:50<t_uint256>",
+          "src": "1487:29:42"
+        },
+        {
+          "contract": "ERC721Pausable",
+          "path": "contracts/token/ERC721/ERC721Pausable.sol",
+          "label": "______gap",
+          "astId": 13076,
+          "type": "t_array:50<t_uint256>",
+          "src": "865:29:144"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [
+          {
+            "contract": "ERC721",
+            "path": "contracts/token/ERC721/ERC721.sol",
+            "label": "_ownedTokensCount",
+            "astId": 11725,
+            "type": "t_mapping<t_struct<Counters.Counter>>",
+            "src": "1100:63:136"
+          },
+          {
+            "contract": "MinterRole",
+            "path": "contracts/access/roles/MinterRole.sol",
+            "label": "_minters",
+            "astId": 1455,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1578,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:11"
+          }
+        ],
+        "storageDiff": []
+      }
+    },
+    "StandaloneERC20": {
+      "address": "0xaabC7f35AF87B61148cD4047828cC7FC0707D771",
+      "constructorCode": "6080604052612b68806100136000396000f3fe",
+      "bodyBytecodeHash": "47dc17b93316f8df939ac42afd023448ba98f3c8d3f7e4240f118217a4e3020e",
+      "localBytecodeHash": "92d11f5376cafd394027eedcf15b21805f9e8e4293a286b74e8c44620c324b34",
+      "deployedBytecodeHash": "92d11f5376cafd394027eedcf15b21805f9e8e4293a286b74e8c44620c324b34",
+      "types": {
+        "t_bool": {
+          "id": "t_bool",
+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
+          "id": "t_uint256",
+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_string": {
+          "id": "t_string",
+          "kind": "elementary",
+          "label": "string"
+        },
+        "t_uint8": {
+          "id": "t_uint8",
+          "kind": "elementary",
+          "label": "uint8"
+        },
+        "t_mapping<t_uint256>": {
+          "id": "t_mapping<t_uint256>",
+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_struct<Roles.Role>": {
+          "id": "t_struct<Roles.Role>",
+          "kind": "struct",
+          "label": "Roles.Role",
+          "members": [
+            {
+              "label": "bearer",
+              "astId": 1222,
+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        },
+        "t_mapping<t_bool>": {
+          "id": "t_mapping<t_bool>",
+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13536,
+          "type": "t_bool",
+          "src": "757:24:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13538,
+          "type": "t_bool",
+          "src": "876:25:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13594,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:154"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_name",
+          "astId": 10854,
+          "type": "t_string",
+          "src": "397:20:129"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_symbol",
+          "astId": 10856,
+          "type": "t_string",
+          "src": "423:22:129"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_decimals",
+          "astId": 10858,
+          "type": "t_uint8",
+          "src": "451:23:129"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "______gap",
+          "astId": 10910,
+          "type": "t_array:50<t_uint256>",
+          "src": "1112:29:129"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_balances",
+          "astId": 10355,
+          "type": "t_mapping<t_uint256>",
+          "src": "809:46:126"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_allowances",
+          "astId": 10361,
+          "type": "t_mapping<t_uint256>",
+          "src": "862:69:126"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_totalSupply",
+          "astId": 10363,
+          "type": "t_uint256",
+          "src": "938:28:126"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "______gap",
+          "astId": 10728,
+          "type": "t_array:50<t_uint256>",
+          "src": "7822:29:126"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1455,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1555,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:10"
+        },
+        {
+          "contract": "ERC20Mintable",
+          "path": "contracts/token/ERC20/ERC20Mintable.sol",
+          "label": "______gap",
+          "astId": 10959,
+          "type": "t_array:50<t_uint256>",
+          "src": "760:29:130"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1578,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1678,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5445,
+          "type": "t_bool",
+          "src": "406:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5526,
+          "type": "t_array:50<t_uint256>",
+          "src": "1487:29:42"
+        },
+        {
+          "contract": "ERC20Pausable",
+          "path": "contracts/token/ERC20/ERC20Pausable.sol",
+          "label": "______gap",
+          "astId": 11082,
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+}

.openzeppelin/mainnet.json

@@ -0,0 +1,923 @@
+{
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+          "label": "_symbol",
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+          "type": "t_string",
+          "src": "423:22:129"
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+          "label": "_decimals",
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+        },
+        {
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+          "label": "______gap",
+          "astId": 10910,
+          "type": "t_array:50<t_uint256>",
+          "src": "1112:29:129"
+        },
+        {
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+        },
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+        },
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+          "astId": 1555,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:10"
+        },
+        {
+          "contract": "ERC20Mintable",
+          "path": "contracts/token/ERC20/ERC20Mintable.sol",
+          "label": "______gap",
+          "astId": 10959,
+          "type": "t_array:50<t_uint256>",
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+        },
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+          "label": "_tokenOwner",
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+          "src": "1100:63:136"
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+        },
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+          "src": "622:53:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
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+          "label": "_allTokens",
+          "astId": 12323,
+          "type": "t_array:dyn<t_uint256>",
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+        },
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+          "label": "_allTokensIndex",
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+          "type": "t_mapping<t_uint256>",
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+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "______gap",
+          "astId": 12656,
+          "type": "t_array:50<t_uint256>",
+          "src": "8858:29:138"
+        },
+        {
+          "contract": "ERC721Metadata",
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+          "label": "_name",
+          "astId": 12726,
+          "type": "t_string",
+          "src": "323:20:141"
+        },
+        {
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+          "label": "_symbol",
+          "astId": 12728,
+          "type": "t_string",
+          "src": "370:22:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_tokenURIs",
+          "astId": 12732,
+          "type": "t_mapping<t_string>",
+          "src": "438:45:141"
+        },
+        {
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+          "label": "______gap",
+          "astId": 12861,
+          "type": "t_array:50<t_uint256>",
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+        },
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+        },
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+          "label": "______gap",
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+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:10"
+        },
+        {
+          "contract": "ERC721MetadataMintable",
+          "path": "contracts/token/ERC721/ERC721MetadataMintable.sol",
+          "label": "______gap",
+          "astId": 12931,
+          "type": "t_array:50<t_uint256>",
+          "src": "1055:29:142"
+        },
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+          "label": "_pausers",
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+          "type": "t_struct<Roles.Role>",
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+        },
+        {
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+          "astId": 1678,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:11"
+        },
+        {
+          "contract": "Pausable",
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+          "label": "_paused",
+          "astId": 5445,
+          "type": "t_bool",
+          "src": "406:20:42"
+        },
+        {
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+          "label": "______gap",
+          "astId": 5526,
+          "type": "t_array:50<t_uint256>",
+          "src": "1487:29:42"
+        },
+        {
+          "contract": "ERC721Pausable",
+          "path": "contracts/token/ERC721/ERC721Pausable.sol",
+          "label": "______gap",
+          "astId": 13076,
+          "type": "t_array:50<t_uint256>",
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+        "uninitializedBaseContracts": [],
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+            "label": "_ownedTokensCount",
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+            "type": "t_mapping<t_struct<Counters.Counter>>",
+            "src": "1100:63:136"
+          },
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+            "label": "_minters",
+            "astId": 1455,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1578,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:11"
+          }
+        ],
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+    }
+  },
+  "solidityLibs": {},
+  "proxies": {},
+  "manifestVersion": "2.2",
+  "frozen": true,
+  "app": {
+    "address": "0x2Ba1a8C7352a5B5Ea3ea3408F89e1bA7920d36CE"
+  },
+  "package": {
+    "address": "0x778dddF23Ec1B5Cb18394c6C110480CaaDB3B0f6"
+  },
+  "provider": {
+    "address": "0xfeEdcb2Bd3b5EAA52aA64063ce16ECc4987da658"
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+}

.openzeppelin/project.json

@@ -0,0 +1,19 @@
+{
+  "manifestVersion": "2.2",
+  "name": "@openzeppelin/contracts-ethereum-package",
+  "publish": true,
+  "version": "2.2.3",
+  "contracts": {
+    "StandaloneERC20": "StandaloneERC20",
+    "StandaloneERC721": "StandaloneERC721",
+    "TokenVesting": "TokenVesting",
+    "PaymentSplitter": "PaymentSplitter"
+  },
+  "dependencies": {},
+  "compiler": {
+    "manager": "truffle",
+    "compilerSettings": {
+      "optimizer": {}
+    }
+  }
+}

.openzeppelin/rinkeby.json

@@ -0,0 +1,923 @@
+{
+  "contracts": {
+    "StandaloneERC20": {
+      "address": "0x73fa66eA7944a51453e78970dC84634D91e4848c",
+      "constructorCode": "6080604052612b68806100136000396000f3fe",
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+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13538,
+          "type": "t_bool",
+          "src": "876:25:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13594,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:154"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "_supportedInterfaces",
+          "astId": 5232,
+          "type": "t_mapping<t_bool>",
+          "src": "511:52:39"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "______gap",
+          "astId": 5276,
+          "type": "t_array:50<t_uint256>",
+          "src": "1244:29:39"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenOwner",
+          "astId": 11717,
+          "type": "t_mapping<t_address>",
+          "src": "886:48:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenApprovals",
+          "astId": 11721,
+          "type": "t_mapping<t_address>",
+          "src": "990:52:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_ownedTokensCount",
+          "astId": 11725,
+          "type": "t_mapping<t_struct<Counters.Counter>>",
+          "src": "1100:63:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_operatorApprovals",
+          "astId": 11731,
+          "type": "t_mapping<t_bool>",
+          "src": "1218:73:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "______gap",
+          "astId": 12258,
+          "type": "t_array:50<t_uint256>",
+          "src": "11985:29:136"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokens",
+          "astId": 12316,
+          "type": "t_mapping<t_array:dyn<t_uint256>>",
+          "src": "502:50:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokensIndex",
+          "astId": 12320,
+          "type": "t_mapping<t_uint256>",
+          "src": "622:53:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokens",
+          "astId": 12323,
+          "type": "t_array:dyn<t_uint256>",
+          "src": "736:28:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokensIndex",
+          "astId": 12327,
+          "type": "t_mapping<t_uint256>",
+          "src": "835:51:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "______gap",
+          "astId": 12656,
+          "type": "t_array:50<t_uint256>",
+          "src": "8858:29:138"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_name",
+          "astId": 12726,
+          "type": "t_string",
+          "src": "323:20:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_symbol",
+          "astId": 12728,
+          "type": "t_string",
+          "src": "370:22:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_tokenURIs",
+          "astId": 12732,
+          "type": "t_mapping<t_string>",
+          "src": "438:45:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "______gap",
+          "astId": 12861,
+          "type": "t_array:50<t_uint256>",
+          "src": "2891:29:141"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1455,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1555,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:10"
+        },
+        {
+          "contract": "ERC721MetadataMintable",
+          "path": "contracts/token/ERC721/ERC721MetadataMintable.sol",
+          "label": "______gap",
+          "astId": 12931,
+          "type": "t_array:50<t_uint256>",
+          "src": "1055:29:142"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1578,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1678,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5445,
+          "type": "t_bool",
+          "src": "406:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5526,
+          "type": "t_array:50<t_uint256>",
+          "src": "1487:29:42"
+        },
+        {
+          "contract": "ERC721Pausable",
+          "path": "contracts/token/ERC721/ERC721Pausable.sol",
+          "label": "______gap",
+          "astId": 13076,
+          "type": "t_array:50<t_uint256>",
+          "src": "865:29:144"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [
+          {
+            "contract": "ERC721",
+            "path": "contracts/token/ERC721/ERC721.sol",
+            "label": "_ownedTokensCount",
+            "astId": 11725,
+            "type": "t_mapping<t_struct<Counters.Counter>>",
+            "src": "1100:63:136"
+          },
+          {
+            "contract": "MinterRole",
+            "path": "contracts/access/roles/MinterRole.sol",
+            "label": "_minters",
+            "astId": 1455,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1578,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:11"
+          }
+        ],
+        "storageDiff": []
+      }
+    }
+  },
+  "solidityLibs": {},
+  "proxies": {},
+  "manifestVersion": "2.2",
+  "frozen": true,
+  "app": {
+    "address": "0x291439E6444dAEc9e47Ae359Aa79FD1811A42679"
+  },
+  "package": {
+    "address": "0xa44bb80b290dE8a465d17B14269dF53CF0B9Bf4f"
+  },
+  "provider": {
+    "address": "0xb3356E12194d3A8a847bA76313a83718d6729eCf"
+  },
+  "version": "2.2.3"
+}

.openzeppelin/ropsten.json

@@ -0,0 +1,923 @@
+{
+  "contracts": {
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+      "address": "0x87C4eE5Ce946291BCcF4ac3333f44CFfDE26f98a",
+      "constructorCode": "60806040526114e7806100136000396000f3fe",
+      "bodyBytecodeHash": "c304cafc8a928423a24501d5e106dca14630e603c16dca8d9cc17569984beaa2",
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+      "deployedBytecodeHash": "eb377fbbff249e0f05823b8b4312d3caddce2867da947eb7a0ad85800e4db993",
+      "types": {
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+          "label": "bool"
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+          "label": "uint256"
+        },
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+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_address": {
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+          "kind": "elementary",
+          "label": "address"
+        },
+        "t_mapping<t_uint256>": {
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+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_mapping<t_bool>": {
+          "id": "t_mapping<t_bool>",
+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        }
+      },
+      "storage": [
+        {
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+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13536,
+          "type": "t_bool",
+          "src": "757:24:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13538,
+          "type": "t_bool",
+          "src": "876:25:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13594,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:154"
+        },
+        {
+          "contract": "Ownable",
+          "path": "contracts/ownership/Ownable.sol",
+          "label": "_owner",
+          "astId": 9431,
+          "type": "t_address",
+          "src": "356:22:119"
+        },
+        {
+          "contract": "Ownable",
+          "path": "contracts/ownership/Ownable.sol",
+          "label": "______gap",
+          "astId": 9542,
+          "type": "t_array:50<t_uint256>",
+          "src": "2318:29:119"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_beneficiary",
+          "astId": 4701,
+          "type": "t_address",
+          "src": "1148:28:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_cliff",
+          "astId": 4703,
+          "type": "t_uint256",
+          "src": "1278:22:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_start",
+          "astId": 4705,
+          "type": "t_uint256",
+          "src": "1306:22:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_duration",
+          "astId": 4707,
+          "type": "t_uint256",
+          "src": "1334:25:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_revocable",
+          "astId": 4709,
+          "type": "t_bool",
+          "src": "1366:23:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_released",
+          "astId": 4713,
+          "type": "t_mapping<t_uint256>",
+          "src": "1396:46:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "_revoked",
+          "astId": 4717,
+          "type": "t_mapping<t_bool>",
+          "src": "1448:42:36"
+        },
+        {
+          "contract": "TokenVesting",
+          "path": "contracts/drafts/TokenVesting.sol",
+          "label": "______gap",
+          "astId": 5059,
+          "type": "t_array:50<t_uint256>",
+          "src": "5852:29:36"
+        }
+      ],
+      "warnings": {
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+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [],
+        "storageDiff": []
+      }
+    },
+    "PaymentSplitter": {
+      "address": "0x621DB5C5B8A6CFd829bDAe49D0a2c2e90797Fc38",
+      "constructorCode": "6080604052610bf2806100136000396000f3fe",
+      "bodyBytecodeHash": "f80b1634ecca81b01cd4155b3ceba5e85979d18489c685ce4bc0f3e16e50ed3d",
+      "localBytecodeHash": "4fffe4f76deb208e21319fb0b5446ab2b82b2ec221097e510f0ee982a12717b6",
+      "deployedBytecodeHash": "4fffe4f76deb208e21319fb0b5446ab2b82b2ec221097e510f0ee982a12717b6",
+      "types": {
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+          "kind": "elementary",
+          "label": "bool"
+        },
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+          "label": "uint256"
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+          "label": "address"
+        },
+        "t_array:dyn<t_address>": {
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+          "valueType": "t_address",
+          "length": "dyn",
+          "kind": "array",
+          "label": "address[]"
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13536,
+          "type": "t_bool",
+          "src": "757:24:154"
+        },
+        {
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+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13538,
+          "type": "t_bool",
+          "src": "876:25:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13594,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:154"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_totalShares",
+          "astId": 9654,
+          "type": "t_uint256",
+          "src": "593:28:121"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_totalReleased",
+          "astId": 9656,
+          "type": "t_uint256",
+          "src": "627:30:121"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_shares",
+          "astId": 9660,
+          "type": "t_mapping<t_uint256>",
+          "src": "664:43:121"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_released",
+          "astId": 9664,
+          "type": "t_mapping<t_uint256>",
+          "src": "713:45:121"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "_payees",
+          "astId": 9667,
+          "type": "t_array:dyn<t_address>",
+          "src": "764:25:121"
+        },
+        {
+          "contract": "PaymentSplitter",
+          "path": "contracts/payment/PaymentSplitter.sol",
+          "label": "______gap",
+          "astId": 9913,
+          "type": "t_array:50<t_uint256>",
+          "src": "3291:29:121"
+        }
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+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [],
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+      }
+    },
+    "StandaloneERC20": {
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+      "constructorCode": "6080604052612b68806100136000396000f3fe",
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+      "types": {
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+          "label": "bool"
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+          "label": "uint256[50]"
+        },
+        "t_string": {
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+          "label": "uint8"
+        },
+        "t_mapping<t_uint256>": {
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+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_struct<Roles.Role>": {
+          "id": "t_struct<Roles.Role>",
+          "kind": "struct",
+          "label": "Roles.Role",
+          "members": [
+            {
+              "label": "bearer",
+              "astId": 1222,
+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        },
+        "t_mapping<t_bool>": {
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+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13536,
+          "type": "t_bool",
+          "src": "757:24:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13538,
+          "type": "t_bool",
+          "src": "876:25:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13594,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:154"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_name",
+          "astId": 10854,
+          "type": "t_string",
+          "src": "397:20:129"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_symbol",
+          "astId": 10856,
+          "type": "t_string",
+          "src": "423:22:129"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "_decimals",
+          "astId": 10858,
+          "type": "t_uint8",
+          "src": "451:23:129"
+        },
+        {
+          "contract": "ERC20Detailed",
+          "path": "contracts/token/ERC20/ERC20Detailed.sol",
+          "label": "______gap",
+          "astId": 10910,
+          "type": "t_array:50<t_uint256>",
+          "src": "1112:29:129"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_balances",
+          "astId": 10355,
+          "type": "t_mapping<t_uint256>",
+          "src": "809:46:126"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_allowances",
+          "astId": 10361,
+          "type": "t_mapping<t_uint256>",
+          "src": "862:69:126"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "_totalSupply",
+          "astId": 10363,
+          "type": "t_uint256",
+          "src": "938:28:126"
+        },
+        {
+          "contract": "ERC20",
+          "path": "contracts/token/ERC20/ERC20.sol",
+          "label": "______gap",
+          "astId": 10728,
+          "type": "t_array:50<t_uint256>",
+          "src": "7822:29:126"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1455,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1555,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:10"
+        },
+        {
+          "contract": "ERC20Mintable",
+          "path": "contracts/token/ERC20/ERC20Mintable.sol",
+          "label": "______gap",
+          "astId": 10959,
+          "type": "t_array:50<t_uint256>",
+          "src": "760:29:130"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1578,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1678,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5445,
+          "type": "t_bool",
+          "src": "406:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5526,
+          "type": "t_array:50<t_uint256>",
+          "src": "1487:29:42"
+        },
+        {
+          "contract": "ERC20Pausable",
+          "path": "contracts/token/ERC20/ERC20Pausable.sol",
+          "label": "______gap",
+          "astId": 11082,
+          "type": "t_array:50<t_uint256>",
+          "src": "1209:29:131"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [
+          {
+            "contract": "MinterRole",
+            "path": "contracts/access/roles/MinterRole.sol",
+            "label": "_minters",
+            "astId": 1455,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1578,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:11"
+          }
+        ],
+        "storageDiff": [
+          {
+            "action": "rename",
+            "updated": {
+              "index": 8,
+              "contract": "ERC20",
+              "path": "contracts/token/ERC20/ERC20.sol",
+              "label": "_allowances",
+              "astId": 10361,
+              "type": "t_mapping<t_uint256>",
+              "src": "862:69:126"
+            },
+            "original": {
+              "index": 8,
+              "contract": "ERC20",
+              "path": "contracts/token/ERC20/ERC20.sol",
+              "label": "_allowed",
+              "astId": 10245,
+              "type": "t_mapping<t_uint256>",
+              "src": "820:66:125"
+            }
+          }
+        ]
+      }
+    },
+    "StandaloneERC721": {
+      "address": "0xE77B22d034cF85F2F851516D9BdC2fF2D76471D3",
+      "constructorCode": "60806040526139f3806100136000396000f3fe",
+      "bodyBytecodeHash": "33aac4411967c3463cdac9bb7d6d491c9bd9f8338aeb53d8ebe0cf054abb2508",
+      "localBytecodeHash": "16e6da0afa76f1d342939ec26b9213e99b8b707e52b930005971e9d752fdc54a",
+      "deployedBytecodeHash": "16e6da0afa76f1d342939ec26b9213e99b8b707e52b930005971e9d752fdc54a",
+      "types": {
+        "t_bool": {
+          "id": "t_bool",
+          "kind": "elementary",
+          "label": "bool"
+        },
+        "t_uint256": {
+          "id": "t_uint256",
+          "kind": "elementary",
+          "label": "uint256"
+        },
+        "t_array:50<t_uint256>": {
+          "id": "t_array:50<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "50",
+          "kind": "array",
+          "label": "uint256[50]"
+        },
+        "t_mapping<t_bool>": {
+          "id": "t_mapping<t_bool>",
+          "valueType": "t_bool",
+          "label": "mapping(key => bool)",
+          "kind": "mapping"
+        },
+        "t_address": {
+          "id": "t_address",
+          "kind": "elementary",
+          "label": "address"
+        },
+        "t_mapping<t_address>": {
+          "id": "t_mapping<t_address>",
+          "valueType": "t_address",
+          "label": "mapping(key => address)",
+          "kind": "mapping"
+        },
+        "t_struct<Counters.Counter>": {
+          "id": "t_struct<Counters.Counter>",
+          "kind": "struct",
+          "label": "Counters.Counter",
+          "members": [
+            {
+              "label": "_value",
+              "astId": 3662,
+              "type": "t_uint256",
+              "src": "1021:14:30"
+            }
+          ]
+        },
+        "t_mapping<t_struct<Counters.Counter>>": {
+          "id": "t_mapping<t_struct<Counters.Counter>>",
+          "valueType": "t_struct<Counters.Counter>",
+          "label": "mapping(key => Counters.Counter)",
+          "kind": "mapping"
+        },
+        "t_array:dyn<t_uint256>": {
+          "id": "t_array:dyn<t_uint256>",
+          "valueType": "t_uint256",
+          "length": "dyn",
+          "kind": "array",
+          "label": "uint256[]"
+        },
+        "t_mapping<t_array:dyn<t_uint256>>": {
+          "id": "t_mapping<t_array:dyn<t_uint256>>",
+          "valueType": "t_array:dyn<t_uint256>",
+          "label": "mapping(key => uint256[])",
+          "kind": "mapping"
+        },
+        "t_mapping<t_uint256>": {
+          "id": "t_mapping<t_uint256>",
+          "valueType": "t_uint256",
+          "label": "mapping(key => uint256)",
+          "kind": "mapping"
+        },
+        "t_string": {
+          "id": "t_string",
+          "kind": "elementary",
+          "label": "string"
+        },
+        "t_mapping<t_string>": {
+          "id": "t_mapping<t_string>",
+          "valueType": "t_string",
+          "label": "mapping(key => string)",
+          "kind": "mapping"
+        },
+        "t_struct<Roles.Role>": {
+          "id": "t_struct<Roles.Role>",
+          "kind": "struct",
+          "label": "Roles.Role",
+          "members": [
+            {
+              "label": "bearer",
+              "astId": 1222,
+              "type": "t_mapping<t_bool>",
+              "src": "150:32:8"
+            }
+          ]
+        }
+      },
+      "storage": [
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initialized",
+          "astId": 13536,
+          "type": "t_bool",
+          "src": "757:24:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "initializing",
+          "astId": 13538,
+          "type": "t_bool",
+          "src": "876:25:154"
+        },
+        {
+          "contract": "Initializable",
+          "path": "@openzeppelin/upgrades/contracts/Initializable.sol",
+          "label": "______gap",
+          "astId": 13594,
+          "type": "t_array:50<t_uint256>",
+          "src": "1951:29:154"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "_supportedInterfaces",
+          "astId": 5232,
+          "type": "t_mapping<t_bool>",
+          "src": "511:52:39"
+        },
+        {
+          "contract": "ERC165",
+          "path": "contracts/introspection/ERC165.sol",
+          "label": "______gap",
+          "astId": 5276,
+          "type": "t_array:50<t_uint256>",
+          "src": "1244:29:39"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenOwner",
+          "astId": 11717,
+          "type": "t_mapping<t_address>",
+          "src": "886:48:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_tokenApprovals",
+          "astId": 11721,
+          "type": "t_mapping<t_address>",
+          "src": "990:52:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_ownedTokensCount",
+          "astId": 11725,
+          "type": "t_mapping<t_struct<Counters.Counter>>",
+          "src": "1100:63:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "_operatorApprovals",
+          "astId": 11731,
+          "type": "t_mapping<t_bool>",
+          "src": "1218:73:136"
+        },
+        {
+          "contract": "ERC721",
+          "path": "contracts/token/ERC721/ERC721.sol",
+          "label": "______gap",
+          "astId": 12258,
+          "type": "t_array:50<t_uint256>",
+          "src": "11985:29:136"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokens",
+          "astId": 12316,
+          "type": "t_mapping<t_array:dyn<t_uint256>>",
+          "src": "502:50:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_ownedTokensIndex",
+          "astId": 12320,
+          "type": "t_mapping<t_uint256>",
+          "src": "622:53:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokens",
+          "astId": 12323,
+          "type": "t_array:dyn<t_uint256>",
+          "src": "736:28:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "_allTokensIndex",
+          "astId": 12327,
+          "type": "t_mapping<t_uint256>",
+          "src": "835:51:138"
+        },
+        {
+          "contract": "ERC721Enumerable",
+          "path": "contracts/token/ERC721/ERC721Enumerable.sol",
+          "label": "______gap",
+          "astId": 12656,
+          "type": "t_array:50<t_uint256>",
+          "src": "8858:29:138"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_name",
+          "astId": 12726,
+          "type": "t_string",
+          "src": "323:20:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_symbol",
+          "astId": 12728,
+          "type": "t_string",
+          "src": "370:22:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "_tokenURIs",
+          "astId": 12732,
+          "type": "t_mapping<t_string>",
+          "src": "438:45:141"
+        },
+        {
+          "contract": "ERC721Metadata",
+          "path": "contracts/token/ERC721/ERC721Metadata.sol",
+          "label": "______gap",
+          "astId": 12861,
+          "type": "t_array:50<t_uint256>",
+          "src": "2891:29:141"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "_minters",
+          "astId": 1455,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:10"
+        },
+        {
+          "contract": "MinterRole",
+          "path": "contracts/access/roles/MinterRole.sol",
+          "label": "______gap",
+          "astId": 1555,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:10"
+        },
+        {
+          "contract": "ERC721MetadataMintable",
+          "path": "contracts/token/ERC721/ERC721MetadataMintable.sol",
+          "label": "______gap",
+          "astId": 12931,
+          "type": "t_array:50<t_uint256>",
+          "src": "1055:29:142"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "_pausers",
+          "astId": 1578,
+          "type": "t_struct<Roles.Role>",
+          "src": "327:27:11"
+        },
+        {
+          "contract": "PauserRole",
+          "path": "contracts/access/roles/PauserRole.sol",
+          "label": "______gap",
+          "astId": 1678,
+          "type": "t_array:50<t_uint256>",
+          "src": "1193:29:11"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "_paused",
+          "astId": 5445,
+          "type": "t_bool",
+          "src": "406:20:42"
+        },
+        {
+          "contract": "Pausable",
+          "path": "contracts/lifecycle/Pausable.sol",
+          "label": "______gap",
+          "astId": 5526,
+          "type": "t_array:50<t_uint256>",
+          "src": "1487:29:42"
+        },
+        {
+          "contract": "ERC721Pausable",
+          "path": "contracts/token/ERC721/ERC721Pausable.sol",
+          "label": "______gap",
+          "astId": 13076,
+          "type": "t_array:50<t_uint256>",
+          "src": "865:29:144"
+        }
+      ],
+      "warnings": {
+        "hasConstructor": false,
+        "hasSelfDestruct": false,
+        "hasDelegateCall": false,
+        "hasInitialValuesInDeclarations": false,
+        "uninitializedBaseContracts": [],
+        "storageUncheckedVars": [
+          {
+            "contract": "ERC721",
+            "path": "contracts/token/ERC721/ERC721.sol",
+            "label": "_ownedTokensCount",
+            "astId": 11725,
+            "type": "t_mapping<t_struct<Counters.Counter>>",
+            "src": "1100:63:136"
+          },
+          {
+            "contract": "MinterRole",
+            "path": "contracts/access/roles/MinterRole.sol",
+            "label": "_minters",
+            "astId": 1455,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:10"
+          },
+          {
+            "contract": "PauserRole",
+            "path": "contracts/access/roles/PauserRole.sol",
+            "label": "_pausers",
+            "astId": 1578,
+            "type": "t_struct<Roles.Role>",
+            "src": "327:27:11"
+          }
+        ],
+        "storageDiff": []
+      }
+    }
+  },
+  "solidityLibs": {},
+  "proxies": {},
+  "manifestVersion": "2.2",
+  "frozen": true,
+  "app": {
+    "address": "0x27a09abCA2c4d9F914dbC7BeA164b0e6b74Ce7a9"
+  },
+  "package": {
+    "address": "0x2a9e7B63514438906A83a1e320dBBD814D417002"
+  },
+  "provider": {
+    "address": "0xbC1628cAE5Ed8892b030864eb8e37e70d0a9594C"
+  },
+  "version": "2.2.3"
+}

.travis.yml

@@ -1,53 +0,0 @@
-dist: trusty
-sudo: false
-group: beta
-language: node_js
-node_js:
-  - "8"
-
-cache:
-  directories:
-    - node_modules
-
-jobs:
-  # XXX fast_finish doesn't work with stages yet. See
-  # https://github.com/travis-ci/travis-ci/issues/8425
-  # --elopio - 20180531
-  fast_finish: true
-  allow_failures:
-    - env: SOLC_NIGHTLY=true
-  include:
-    - stage: tests
-      name: "Linter"
-      script: npm run lint
-
-    - stage: tests
-      name: "Unit tests"
-      script: npm run test
-
-    - stage: tests
-      name: "Unit tests with coverage report"
-      script: npm run test
-      env: SOLIDITY_COVERAGE=true
-
-    - stage: tests
-      name: "Unit tests using solc nightly"
-      script: npm run test
-      env: SOLC_NIGHTLY=true
-
-    - stage: update docs
-      if: tag =~ ^v[0-9]+\.[0-9]+\.[0-9]+$
-      addons:
-        apt:
-          packages:
-            - curl
-      script:
-        - ./scripts/ci/trigger_docs_update "${TRAVIS_TAG}"
-
-notifications:
-  slack:
-    rooms:
-      - secure: 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
-    on_success: change
-    on_failure: always
-    on_pull_requests: false

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## 2.2.2 (2019-08-12)
+
+### New features:
+ * Facilities to make metatransaction-enabled contracts through the Gas Station Network. Backported from [#1844](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/1844).
+
+## 2.2.1 (2019-07-22)
+
+### Changes:
+* Renamed package to `@openzeppelin/contracts-ethereum-package`. ([#54](https://github.com/OpenZeppelin/openzeppelin-contracts-ethereum-package/pull/54))
+
 ## 2.2.0 (2019-03-14)
 
 ### New features:

README.md

@@ -1,42 +1,98 @@
-# <img src="logo.png" alt="OpenZeppelin" width="400px">
+# <img src="logo.png" alt="OpenZeppelin" height="40px">
 
-[![NPM Package](https://img.shields.io/npm/v/openzeppelin-solidity.svg?style=flat-square)](https://www.npmjs.org/package/openzeppelin-solidity)
-[![Build Status](https://travis-ci.com/OpenZeppelin/openzeppelin-solidity.svg?branch=master)](https://travis-ci.com/OpenZeppelin/openzeppelin-solidity)
-[![Coverage Status](https://coveralls.io/repos/github/OpenZeppelin/openzeppelin-solidity/badge.svg?branch=master)](https://coveralls.io/github/OpenZeppelin/openzeppelin-solidity?branch=master)
+## OpenZeppelin Contracts Ethereum Package
 
-**OpenZeppelin is a library for secure smart contract development.** It provides implementations of standards like ERC20 and ERC721 which you can deploy as-is or extend to suit your needs, as well as Solidity components to build custom contracts and more complex decentralized systems.
+[![NPM Package](https://img.shields.io/npm/v/@openzeppelin/contracts-ethereum-package.svg)](https://www.npmjs.org/package/@openzeppelin/contracts-ethereum-package)
+[![Build Status](https://circleci.com/gh/OpenZeppelin/openzeppelin-contracts-ethereum-package.svg?style=shield)](https://circleci.com/gh/OpenZeppelin/openzeppelin-contracts-ethereum-package)
+
+**OpenZeppelin Contracts is a library for secure smart contract development.** It provides implementations of standards like ERC20 and ERC721 which you can deploy as-is or extend to suit your needs, as well as Solidity components to build custom contracts and more complex decentralized systems.
+
+This fork of OpenZeppelin is set up as a **reusable Ethereum Package**. It is deployed to the kovan, rinkeby, and ropsten test networks, as well as to the main Ethereum network. You can reuse any of the pre-deployed on-chain contracts by simply linking to them using the [OpenZeppelin SDK](https://github.com/openzeppelin/openzeppelin-sdk), or reuse their Solidity source code as with the [vanilla version of OpenZeppelin Contracts](https://github.com/OpenZeppelin/openzeppelin-contracts).
+
+## Differences with openzeppelin-contracts
+
+This package contains the same contracts as the vanilla [openzeppelin-contracts](https://github.com/openZeppelin/openzeppelin-contracts). The main difference is that _all contracts in this package are potentially upgradeable_: you will notice that no contracts have constructors defined, but use [initializer functions](https://docs.zeppelinos.org/docs/writing_contracts.html#initializers) instead. Also, this package is set up as an Ethereum package, and provides a small set of pre-deployed logic contracts that can be used directly via the OpenZeppelin SDK, without needing to deploy them again.
+
+All in all, **you should use this package instead of openzeppelin-solidity if you are managing your project via the OpenZeppelin CLI**.
 
 ## Install
 
 ```
-npm install openzeppelin-solidity
+npm install @openzeppelin/contracts-ethereum-package
 ```
 
-## Usage
+## Deployed logic contracts
 
-To write your custom contracts, import ours and extend them through inheritance.
+- [StandaloneERC20](contracts/token/ERC20/StandaloneERC20.sol): ERC20 token implementation, optionally mintable and pausable.
+- [StandaloneERC721](contracts/token/ERC721/StandaloneERC721.sol): ERC721 non-fungible token implementation with metadata and enumerable extensions, optionally mintable and pausable.
+- [TokenVesting](contracts/drafts/TokenVesting.sol): tToken holder contract that can release its token balance gradually like a typical vesting scheme, with a cliff and vesting period, optionally revocable.
+- [PaymentSplitter](contracts/payment/PaymentSplitter.sol): Splits payments among a group of addresses proportionately to some number of shares they own.
+
+## Using via the OpenZeppelin CLI
+
+You can easily create upgradeable instances of any of the logic contracts listed above using the OpenZeppelin CLI. This will rely on the pre-deployed instances in mainnet, kovan, ropsten, or rinkeby, greatly reducing your gas deployment costs. To do this, just [create a new OpenZeppelin SDK project](https://docs.zeppelinos.org/docs/deploying.html) and [link to this package](https://docs.zeppelinos.org/docs/linking.html).
+
+```bash
+$ npm install -g @openzeppelin/cli
+$ openzeppelin init
+$ openzeppelin link @openzeppelin/contracts-ethereum-package
+> Installing...
+$ openzeppelin create @openzeppelin/contracts-ethereum-package/StandaloneERC20
+> Creating...
+```
+
+To create an instance of a contract, use the `openzeppelin create` command. As an example, you can run the following to create an upgradeable ERC20 named MyToken, with symbol TKN and 8 decimals, and an initial supply of 100 tokens assigned to the address HOLDER, with a MINTER and a PAUSER. Remember to replace $HOLDER, $MINTER, and $PAUSER with actual addresses when you run this command; you can specify more than one (or none at all) minters and pausers.
+
+```
+$ openzeppelin create
+? Pick a contract to instantiate: @openzeppelin/contracts-ethereum-package/StandaloneERC20
+? Pick a network: development
+✓ Deploying @openzeppelin/contracts-ethereum-package dependency to network
+? Do you want to call a function on the instance after creating it?: Yes
+? Select which function: * initialize(name: string, symbol: string, decimals: uint8, initialSupply: uint256, initialHolder: address, minters: address[], pausers: address[])
+? name (string): MyToken
+? symbol (string): MYT
+? decimals (uint8): 18
+? initialSupply (uint256): 100e18
+? initialHolder (address): 0x90f8bf6a479f320ead074411a4b0e7944ea8c9c1
+? minters (address[]):
+? pausers (address[]):
+✓ Setting everything up to create contract instances
+✓ Instance created at 0x2612Af3A521c2df9EAF28422Ca335b04AdF3ac66
+```
+
+OpenZeppelin will create an upgradeable ERC20 instance and keep track of its address in the `.openzeppelin/rinkeby.json` file. Should you update your version of the openzeppelin contracts ethereum package later down the road, you can simply run `openzeppelin update` to upgrade all your ERC20 instances to the latest version.
+
+You can also deploy a ERC721 token by choosing the `StandaloneERC721` contract when running `openzeppelin create`. Refer to the `initialize` function of each of the predeployed logic contracts to see which parameters are required for initialization.
+
+## Extending contracts
+
+If you prefer to write your custom contracts, import the ones from this package and extend them through inheritance. Note that **you must use this package and not `@openzeppelin/contracts` if you are [writing upgradeable contracts](https://docs.zeppelinos.org/docs/writing_contracts.html)**.
 
 ```solidity
 pragma solidity ^0.5.0;
 
-import 'openzeppelin-solidity/contracts/token/ERC721/ERC721Full.sol';
-import 'openzeppelin-solidity/contracts/token/ERC721/ERC721Mintable.sol';
+import '@openzeppelin/upgrades/contracts/Initializable.sol';
+import '@openzeppelin/contracts-ethereum-package/contracts/token/ERC721/ERC721Full.sol';
+import '@openzeppelin/contracts-ethereum-package/contracts/token/ERC721/ERC721Mintable.sol';
 
-contract MyNFT is ERC721Full, ERC721Mintable {
-  constructor() ERC721Full("MyNFT", "MNFT") public {
+contract MyNFT is Initializable, ERC721Full, ERC721Mintable {
+  function initialize() public initializer {
+    ERC721.initialize();
+    ERC721Enumerable.initialize();
+    ERC721Metadata.initialize("MyNFT", "MNFT");
+    ERC721Mintable.initialize(msg.sender);
   }
 }
 ```
 
-> You need an ethereum development framework for the above import statements to work! Check out these guides for [Truffle] or [Embark].
-
-On our site you will find a few [guides] to learn about the different parts of OpenZeppelin, as well as [documentation for the API][API docs]. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in [our Slack][Slack].
+On our site you will find a few [guides] to learn about the different parts of OpenZeppelin, as well as [documentation for the API][API docs]. Keep in mind that the API docs are work in progress, and don’t hesitate to ask questions in [our forum][forum].
 
 ## Security
 
-OpenZeppelin the project is maintained by [Zeppelin] the company, and developed following our high standards for code quality and security. OpenZeppelin is meant to provide tested and community-audited code, but please use common sense when doing anything that deals with real money! We take no responsibility for your implementation decisions and any security problems you might experience.
+OpenZeppelin Contracts is maintained by [OpenZeppelin](https://openzeppelin.com) the company, and developed following our high standards for code quality and security. OpenZeppelin Contracts is meant to provide tested and community-audited code, but please use common sense when doing anything that deals with real money! We take no responsibility for your implementation decisions and any security problems you might experience.
 
-The core development principles and strategies that OpenZeppelin is based on include: security in depth, simple and modular code, clarity-driven naming conventions, comprehensive unit testing, pre-and-post-condition sanity checks, code consistency, and regular audits.
+The core development principles and strategies that OpenZeppelin Contracts is based on include: security in depth, simple and modular code, clarity-driven naming conventions, comprehensive unit testing, pre-and-post-condition sanity checks, code consistency, and regular audits.
 
 The latest audit was done on October 2018 on version 2.0.0.
 
@@ -50,11 +106,7 @@ OpenZeppelin exists thanks to its contributors. There are many ways you can part
 
 OpenZeppelin is released under the [MIT License](LICENSE).
 
-
-[API docs]: https://openzeppelin.org/api/docs/token_ERC721_ERC721BasicToken.html
-[guides]: https://openzeppelin.org/api/docs/get-started.html
-[Slack]: https://slack.openzeppelin.org
-[Zeppelin]: https://zeppelin.solutions
+[API docs]: https://docs.openzeppelin.org/v2.3.0/api/token/erc20
+[guides]: https://docs.openzeppelin.org/v2.3.0/get-started
+[forum]: https://forum.zeppelin.solutions
 [contribution guide]: CONTRIBUTING.md
-[Truffle]: https://truffleframework.com/docs/truffle/quickstart
-[Embark]: https://embark.status.im/docs/quick_start.html

contracts/GSN/Context.sol

@@ -0,0 +1,27 @@
+pragma solidity ^0.5.0;
+
+/*
+ * @dev Provides information about the current execution context, including the
+ * sender of the transaction and its data. While these are generally available
+ * via msg.sender and msg.data, they not should not be accessed in such a direct
+ * manner, since when dealing with GSN meta-transactions the account sending and
+ * paying for execution may not be the actual sender (as far as an application
+ * is concerned).
+ *
+ * This contract is only required for intermediate, library-like contracts.
+ */
+contract Context {
+    // Empty internal constructor, to prevent people from mistakenly deploying
+    // an instance of this contract, with should be used via inheritance.
+    constructor () internal { }
+    // solhint-disable-previous-line no-empty-blocks
+
+    function _msgSender() internal view returns (address) {
+        return msg.sender;
+    }
+
+    function _msgData() internal view returns (bytes memory) {
+        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
+        return msg.data;
+    }
+}

contracts/GSN/GSNContext.sol

@@ -0,0 +1,103 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./Context.sol";
+
+/*
+ * @dev Enables GSN support on `Context` contracts by recognizing calls from
+ * RelayHub and extracting the actual sender and call data from the received
+ * calldata.
+ *
+ * > This contract does not perform all required tasks to implement a GSN
+ * recipient contract: end users should use `GSNRecipient` instead.
+ */
+contract GSNContext is Initializable, Context {
+    // We use a random storage slot to allow proxy contracts to enable GSN support in an upgrade without changing their
+    // storage layout. This value is calculated as: keccak256('gsn.relayhub.address'), minus 1.
+    bytes32 private constant RELAY_HUB_ADDRESS_STORAGE_SLOT = 0x06b7792c761dcc05af1761f0315ce8b01ac39c16cc934eb0b2f7a8e71414f262;
+
+    event RelayHubChanged(address indexed oldRelayHub, address indexed newRelayHub);
+
+    function initialize() public initializer {
+        _upgradeRelayHub(0xD216153c06E857cD7f72665E0aF1d7D82172F494);
+    }
+
+    function _getRelayHub() internal view returns (address relayHub) {
+        bytes32 slot = RELAY_HUB_ADDRESS_STORAGE_SLOT;
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            relayHub := sload(slot)
+        }
+    }
+
+    function _upgradeRelayHub(address newRelayHub) internal {
+        address currentRelayHub = _getRelayHub();
+        require(newRelayHub != address(0), "GSNContext: new RelayHub is the zero address");
+        require(newRelayHub != currentRelayHub, "GSNContext: new RelayHub is the current one");
+
+        emit RelayHubChanged(currentRelayHub, newRelayHub);
+
+        bytes32 slot = RELAY_HUB_ADDRESS_STORAGE_SLOT;
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            sstore(slot, newRelayHub)
+        }
+    }
+
+    // Overrides for Context's functions: when called from RelayHub, sender and
+    // data require some pre-processing: the actual sender is stored at the end
+    // of the call data, which in turns means it needs to be removed from it
+    // when handling said data.
+
+    function _msgSender() internal view returns (address) {
+        if (msg.sender != _getRelayHub()) {
+            return msg.sender;
+        } else {
+            return _getRelayedCallSender();
+        }
+    }
+
+    function _msgData() internal view returns (bytes memory) {
+        if (msg.sender != _getRelayHub()) {
+            return msg.data;
+        } else {
+            return _getRelayedCallData();
+        }
+    }
+
+    function _getRelayedCallSender() private pure returns (address result) {
+        // We need to read 20 bytes (an address) located at array index msg.data.length - 20. In memory, the array
+        // is prefixed with a 32-byte length value, so we first add 32 to get the memory read index. However, doing
+        // so would leave the address in the upper 20 bytes of the 32-byte word, which is inconvenient and would
+        // require bit shifting. We therefore subtract 12 from the read index so the address lands on the lower 20
+        // bytes. This can always be done due to the 32-byte prefix.
+
+        // The final memory read index is msg.data.length - 20 + 32 - 12 = msg.data.length. Using inline assembly is the
+        // easiest/most-efficient way to perform this operation.
+
+        // These fields are not accessible from assembly
+        bytes memory array = msg.data;
+        uint256 index = msg.data.length;
+
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            // Load the 32 bytes word from memory with the address on the lower 20 bytes, and mask those.
+            result := and(mload(add(array, index)), 0xffffffffffffffffffffffffffffffffffffffff)
+        }
+        return result;
+    }
+
+    function _getRelayedCallData() private pure returns (bytes memory) {
+        // RelayHub appends the sender address at the end of the calldata, so in order to retrieve the actual msg.data,
+        // we must strip the last 20 bytes (length of an address type) from it.
+
+        uint256 actualDataLength = msg.data.length - 20;
+        bytes memory actualData = new bytes(actualDataLength);
+
+        for (uint256 i = 0; i < actualDataLength; ++i) {
+            actualData[i] = msg.data[i];
+        }
+
+        return actualData;
+    }
+}

contracts/GSN/GSNRecipient.sol

@@ -0,0 +1,33 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./IRelayRecipient.sol";
+import "./GSNContext.sol";
+import "./bouncers/GSNBouncerBase.sol";
+import "./IRelayHub.sol";
+
+/*
+ * @dev Base GSN recipient contract, adding the recipient interface and enabling
+ * GSN support. Not all interface methods are implemented, derived contracts
+ * must do so themselves.
+ */
+contract GSNRecipient is Initializable, IRelayRecipient, GSNContext, GSNBouncerBase {
+    function initialize() public initializer {
+        GSNContext.initialize();
+    }
+
+    function getHubAddr() public view returns (address) {
+        return _getRelayHub();
+    }
+
+    // This function is view for future-proofing, it may require reading from
+    // storage in the future.
+    function relayHubVersion() public view returns (string memory) {
+        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
+        return "1.0.0";
+    }
+
+    function _withdrawDeposits(uint256 amount, address payable payee) internal {
+        IRelayHub(_getRelayHub()).withdraw(amount, payee);
+    }
+}

contracts/GSN/IRelayHub.sol

@@ -0,0 +1,188 @@
+pragma solidity ^0.5.0;
+
+contract IRelayHub {
+    // Relay management
+
+    // Add stake to a relay and sets its unstakeDelay.
+    // If the relay does not exist, it is created, and the caller
+    // of this function becomes its owner. If the relay already exists, only the owner can call this function. A relay
+    // cannot be its own owner.
+    // All Ether in this function call will be added to the relay's stake.
+    // Its unstake delay will be assigned to unstakeDelay, but the new value must be greater or equal to the current one.
+    // Emits a Staked event.
+    function stake(address relayaddr, uint256 unstakeDelay) external payable;
+
+    // Emited when a relay's stake or unstakeDelay are increased
+    event Staked(address indexed relay, uint256 stake, uint256 unstakeDelay);
+
+    // Registers the caller as a relay.
+    // The relay must be staked for, and not be a contract (i.e. this function must be called directly from an EOA).
+    // Emits a RelayAdded event.
+    // This function can be called multiple times, emitting new RelayAdded events. Note that the received transactionFee
+    // is not enforced by relayCall.
+    function registerRelay(uint256 transactionFee, string memory url) public;
+
+    // Emitted when a relay is registered or re-registerd. Looking at these events (and filtering out RelayRemoved
+    // events) lets a client discover the list of available relays.
+    event RelayAdded(address indexed relay, address indexed owner, uint256 transactionFee, uint256 stake, uint256 unstakeDelay, string url);
+
+    // Removes (deregisters) a relay. Unregistered (but staked for) relays can also be removed. Can only be called by
+    // the owner of the relay. After the relay's unstakeDelay has elapsed, unstake will be callable.
+    // Emits a RelayRemoved event.
+    function removeRelayByOwner(address relay) public;
+
+    // Emitted when a relay is removed (deregistered). unstakeTime is the time when unstake will be callable.
+    event RelayRemoved(address indexed relay, uint256 unstakeTime);
+
+    // Deletes the relay from the system, and gives back its stake to the owner. Can only be called by the relay owner,
+    // after unstakeDelay has elapsed since removeRelayByOwner was called.
+    // Emits an Unstaked event.
+    function unstake(address relay) public;
+
+    // Emitted when a relay is unstaked for, including the returned stake.
+    event Unstaked(address indexed relay, uint256 stake);
+
+    // States a relay can be in
+    enum RelayState {
+        Unknown, // The relay is unknown to the system: it has never been staked for
+        Staked, // The relay has been staked for, but it is not yet active
+        Registered, // The relay has registered itself, and is active (can relay calls)
+        Removed    // The relay has been removed by its owner and can no longer relay calls. It must wait for its unstakeDelay to elapse before it can unstake
+    }
+
+    // Returns a relay's status. Note that relays can be deleted when unstaked or penalized.
+    function getRelay(address relay) external view returns (uint256 totalStake, uint256 unstakeDelay, uint256 unstakeTime, address payable owner, RelayState state);
+
+    // Balance management
+
+    // Deposits ether for a contract, so that it can receive (and pay for) relayed transactions. Unused balance can only
+    // be withdrawn by the contract itself, by callingn withdraw.
+    // Emits a Deposited event.
+    function depositFor(address target) public payable;
+
+    // Emitted when depositFor is called, including the amount and account that was funded.
+    event Deposited(address indexed recipient, address indexed from, uint256 amount);
+
+    // Returns an account's deposits. These can be either a contnract's funds, or a relay owner's revenue.
+    function balanceOf(address target) external view returns (uint256);
+
+    // Withdraws from an account's balance, sending it back to it. Relay owners call this to retrieve their revenue, and
+    // contracts can also use it to reduce their funding.
+    // Emits a Withdrawn event.
+    function withdraw(uint256 amount, address payable dest) public;
+
+    // Emitted when an account withdraws funds from RelayHub.
+    event Withdrawn(address indexed account, address indexed dest, uint256 amount);
+
+    // Relaying
+
+    // Check if the RelayHub will accept a relayed operation. Multiple things must be true for this to happen:
+    //  - all arguments must be signed for by the sender (from)
+    //  - the sender's nonce must be the current one
+    //  - the recipient must accept this transaction (via acceptRelayedCall)
+    // Returns a PreconditionCheck value (OK when the transaction can be relayed), or a recipient-specific error code if
+    // it returns one in acceptRelayedCall.
+    function canRelay(
+        address relay,
+        address from,
+        address to,
+        bytes memory encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes memory signature,
+        bytes memory approvalData
+    ) public view returns (uint256 status, bytes memory recipientContext);
+
+    // Preconditions for relaying, checked by canRelay and returned as the corresponding numeric values.
+    enum PreconditionCheck {
+        OK,                         // All checks passed, the call can be relayed
+        WrongSignature,             // The transaction to relay is not signed by requested sender
+        WrongNonce,                 // The provided nonce has already been used by the sender
+        AcceptRelayedCallReverted,  // The recipient rejected this call via acceptRelayedCall
+        InvalidRecipientStatusCode  // The recipient returned an invalid (reserved) status code
+    }
+
+    // Relays a transaction. For this to suceed, multiple conditions must be met:
+    //  - canRelay must return PreconditionCheck.OK
+    //  - the sender must be a registered relay
+    //  - the transaction's gas price must be larger or equal to the one that was requested by the sender
+    //  - the transaction must have enough gas to not run out of gas if all internal transactions (calls to the
+    // recipient) use all gas available to them
+    //  - the recipient must have enough balance to pay the relay for the worst-case scenario (i.e. when all gas is
+    // spent)
+    //
+    // If all conditions are met, the call will be relayed and the recipient charged. preRelayedCall, the encoded
+    // function and postRelayedCall will be called in order.
+    //
+    // Arguments:
+    //  - from: the client originating the request
+    //  - recipient: the target IRelayRecipient contract
+    //  - encodedFunction: the function call to relay, including data
+    //  - transactionFee: fee (%) the relay takes over actual gas cost
+    //  - gasPrice: gas price the client is willing to pay
+    //  - gasLimit: gas to forward when calling the encoded function
+    //  - nonce: client's nonce
+    //  - signature: client's signature over all previous params, plus the relay and RelayHub addresses
+    //  - approvalData: dapp-specific data forwared to acceptRelayedCall. This value is *not* verified by the Hub, but
+    //    it still can be used for e.g. a signature.
+    //
+    // Emits a TransactionRelayed event.
+    function relayCall(
+        address from,
+        address to,
+        bytes memory encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes memory signature,
+        bytes memory approvalData
+    ) public;
+
+    // Emitted when an attempt to relay a call failed. This can happen due to incorrect relayCall arguments, or the
+    // recipient not accepting the relayed call. The actual relayed call was not executed, and the recipient not charged.
+    // The reason field contains an error code: values 1-10 correspond to PreconditionCheck entries, and values over 10
+    // are custom recipient error codes returned from acceptRelayedCall.
+    event CanRelayFailed(address indexed relay, address indexed from, address indexed to, bytes4 selector, uint256 reason);
+
+    // Emitted when a transaction is relayed. Note that the actual encoded function might be reverted: this will be
+    // indicated in the status field.
+    // Useful when monitoring a relay's operation and relayed calls to a contract.
+    // Charge is the ether value deducted from the recipient's balance, paid to the relay's owner.
+    event TransactionRelayed(address indexed relay, address indexed from, address indexed to, bytes4 selector, RelayCallStatus status, uint256 charge);
+
+    // Reason error codes for the TransactionRelayed event
+    enum RelayCallStatus {
+        OK,                      // The transaction was successfully relayed and execution successful - never included in the event
+        RelayedCallFailed,       // The transaction was relayed, but the relayed call failed
+        PreRelayedFailed,        // The transaction was not relayed due to preRelatedCall reverting
+        PostRelayedFailed,       // The transaction was relayed and reverted due to postRelatedCall reverting
+        RecipientBalanceChanged  // The transaction was relayed and reverted due to the recipient's balance changing
+    }
+
+    // Returns how much gas should be forwarded to a call to relayCall, in order to relay a transaction that will spend
+    // up to relayedCallStipend gas.
+    function requiredGas(uint256 relayedCallStipend) public view returns (uint256);
+
+    // Returns the maximum recipient charge, given the amount of gas forwarded, gas price and relay fee.
+    function maxPossibleCharge(uint256 relayedCallStipend, uint256 gasPrice, uint256 transactionFee) public view returns (uint256);
+
+    // Relay penalization. Any account can penalize relays, removing them from the system immediately, and rewarding the
+    // reporter with half of the relay's stake. The other half is burned so that, even if the relay penalizes itself, it
+    // still loses half of its stake.
+
+    // Penalize a relay that signed two transactions using the same nonce (making only the first one valid) and
+    // different data (gas price, gas limit, etc. may be different). The (unsigned) transaction data and signature for
+    // both transactions must be provided.
+    function penalizeRepeatedNonce(bytes memory unsignedTx1, bytes memory signature1, bytes memory unsignedTx2, bytes memory signature2) public;
+
+    // Penalize a relay that sent a transaction that didn't target RelayHub's registerRelay or relayCall.
+    function penalizeIllegalTransaction(bytes memory unsignedTx, bytes memory signature) public;
+
+    event Penalized(address indexed relay, address sender, uint256 amount);
+
+    function getNonce(address from) external view returns (uint256);
+}
+

contracts/GSN/IRelayRecipient.sol

@@ -0,0 +1,30 @@
+pragma solidity ^0.5.0;
+
+/*
+ * @dev Interface for a contract that will be called via the GSN from RelayHub.
+ */
+contract IRelayRecipient {
+    /**
+     * @dev Returns the address of the RelayHub instance this recipient interacts with.
+     */
+    function getHubAddr() public view returns (address);
+
+    function acceptRelayedCall(
+        address relay,
+        address from,
+        bytes calldata encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes calldata approvalData,
+        uint256 maxPossibleCharge
+    )
+        external
+        view
+        returns (uint256, bytes memory);
+
+    function preRelayedCall(bytes calldata context) external returns (bytes32);
+
+    function postRelayedCall(bytes calldata context, bool success, uint actualCharge, bytes32 preRetVal) external;
+}

contracts/GSN/bouncers/GSNBouncerBase.sol

@@ -0,0 +1,92 @@
+pragma solidity ^0.5.0;
+
+import "../IRelayRecipient.sol";
+
+/*
+ * @dev Base contract used to implement GSNBouncers.
+ *
+ * > This contract does not perform all required tasks to implement a GSN
+ * recipient contract: end users should use `GSNRecipient` instead.
+ */
+contract GSNBouncerBase is IRelayRecipient {
+    uint256 constant private RELAYED_CALL_ACCEPTED = 0;
+    uint256 constant private RELAYED_CALL_REJECTED = 11;
+
+    // How much gas is forwarded to postRelayedCall
+    uint256 constant internal POST_RELAYED_CALL_MAX_GAS = 100000;
+
+    // Base implementations for pre and post relayedCall: only RelayHub can invoke them, and data is forwarded to the
+    // internal hook.
+
+    /**
+     * @dev See `IRelayRecipient.preRelayedCall`.
+     *
+     * This function should not be overriden directly, use `_preRelayedCall` instead.
+     *
+     * * Requirements:
+     *
+     * - the caller must be the `RelayHub` contract.
+     */
+    function preRelayedCall(bytes calldata context) external returns (bytes32) {
+        require(msg.sender == getHubAddr(), "GSNBouncerBase: caller is not RelayHub");
+        return _preRelayedCall(context);
+    }
+
+    /**
+     * @dev See `IRelayRecipient.postRelayedCall`.
+     *
+     * This function should not be overriden directly, use `_postRelayedCall` instead.
+     *
+     * * Requirements:
+     *
+     * - the caller must be the `RelayHub` contract.
+     */
+    function postRelayedCall(bytes calldata context, bool success, uint256 actualCharge, bytes32 preRetVal) external {
+        require(msg.sender == getHubAddr(), "GSNBouncerBase: caller is not RelayHub");
+        _postRelayedCall(context, success, actualCharge, preRetVal);
+    }
+
+    /**
+     * @dev Return this in acceptRelayedCall to proceed with the execution of a relayed call. Note that this contract
+     * will be charged a fee by RelayHub
+     */
+    function _approveRelayedCall() internal pure returns (uint256, bytes memory) {
+        return _approveRelayedCall("");
+    }
+
+    /**
+     * @dev See `GSNBouncerBase._approveRelayedCall`.
+     *
+     * This overload forwards `context` to _preRelayedCall and _postRelayedCall.
+     */
+    function _approveRelayedCall(bytes memory context) internal pure returns (uint256, bytes memory) {
+        return (RELAYED_CALL_ACCEPTED, context);
+    }
+
+    /**
+     * @dev Return this in acceptRelayedCall to impede execution of a relayed call. No fees will be charged.
+     */
+    function _rejectRelayedCall(uint256 errorCode) internal pure returns (uint256, bytes memory) {
+        return (RELAYED_CALL_REJECTED + errorCode, "");
+    }
+
+    // Empty hooks for pre and post relayed call: users only have to define these if they actually use them.
+
+    function _preRelayedCall(bytes memory) internal returns (bytes32) {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    function _postRelayedCall(bytes memory, bool, uint256, bytes32) internal {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    /*
+     * @dev Calculates how much RelaHub will charge a recipient for using `gas` at a `gasPrice`, given a relayer's
+     * `serviceFee`.
+     */
+    function _computeCharge(uint256 gas, uint256 gasPrice, uint256 serviceFee) internal pure returns (uint256) {
+        // The fee is expressed as a percentage. E.g. a value of 40 stands for a 40% fee, so the recipient will be
+        // charged for 1.4 times the spent amount.
+        return (gas * gasPrice * (100 + serviceFee)) / 100;
+    }
+}

contracts/GSN/bouncers/GSNBouncerERC20Fee.sol

@@ -0,0 +1,143 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./GSNBouncerBase.sol";
+import "../../math/SafeMath.sol";
+import "../../ownership/Secondary.sol";
+import "../../token/ERC20/SafeERC20.sol";
+import "../../token/ERC20/ERC20.sol";
+import "../../token/ERC20/ERC20Detailed.sol";
+
+contract GSNBouncerERC20Fee is Initializable, GSNBouncerBase {
+    using SafeERC20 for __unstable__ERC20PrimaryAdmin;
+    using SafeMath for uint256;
+
+    enum GSNBouncerERC20FeeErrorCodes {
+        INSUFFICIENT_BALANCE
+    }
+
+    // We use a random storage slot to allow proxy contracts to enable GSN support in an upgrade without changing their
+    // storage layout. This value is calculated as: keccak256('gsn.bouncer.signature.token'), minus 1.
+    bytes32 constant private TOKEN_STORAGE_SLOT = 0xd918b70a5a5c95a8c0cac8acbdd59e1b4acd0645f53c0461d64b41f8825c8828;
+
+    function initialize(string memory name, string memory symbol, uint8 decimals) public initializer {
+        // TODO: Should we inject this token, instead of creating it, in order to make it upgradeable?
+        // However, that would mean removing it from unstable and making in an official contract
+        _setToken(new __unstable__ERC20PrimaryAdmin(name, symbol, decimals));
+    }
+
+    function token() public view returns (IERC20) {
+        return IERC20(_getToken());
+    }
+
+    function _mint(address account, uint256 amount) internal {
+        _getToken().mint(account, amount);
+    }
+
+    function acceptRelayedCall(
+        address,
+        address from,
+        bytes calldata,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256,
+        uint256,
+        bytes calldata,
+        uint256 maxPossibleCharge
+    )
+        external
+        view
+        returns (uint256, bytes memory)
+    {
+        if (_getToken().balanceOf(from) < maxPossibleCharge) {
+            return _rejectRelayedCall(uint256(GSNBouncerERC20FeeErrorCodes.INSUFFICIENT_BALANCE));
+        }
+
+        return _approveRelayedCall(abi.encode(from, maxPossibleCharge, transactionFee, gasPrice));
+    }
+
+    function _preRelayedCall(bytes memory context) internal returns (bytes32) {
+        (address from, uint256 maxPossibleCharge) = abi.decode(context, (address, uint256));
+
+        // The maximum token charge is pre-charged from the user
+        _getToken().safeTransferFrom(from, address(this), maxPossibleCharge);
+    }
+
+    function _postRelayedCall(bytes memory context, bool, uint256 actualCharge, bytes32) internal {
+        (address from, uint256 maxPossibleCharge, uint256 transactionFee, uint256 gasPrice) =
+            abi.decode(context, (address, uint256, uint256, uint256));
+
+        // actualCharge is an _estimated_ charge, which assumes postRelayedCall will use all available gas.
+        // This implementation's gas cost can be roughly estimated as 10k gas, for the two SSTORE operations in an
+        // ERC20 transfer.
+        uint256 overestimation = _computeCharge(POST_RELAYED_CALL_MAX_GAS.sub(10000), gasPrice, transactionFee);
+        actualCharge = actualCharge.sub(overestimation);
+
+        // After the relayed call has been executed and the actual charge estimated, the excess pre-charge is returned
+        _getToken().safeTransfer(from, maxPossibleCharge.sub(actualCharge));
+    }
+
+    function _getToken() private view returns (__unstable__ERC20PrimaryAdmin token) {
+      bytes32 slot = TOKEN_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        token := sload(slot)
+      }
+    }
+
+    function _setToken(__unstable__ERC20PrimaryAdmin token) private {
+      bytes32 slot = TOKEN_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        sstore(slot, token)
+      }
+    }
+}
+
+/**
+ * @title __unstable__ERC20PrimaryAdmin
+ * @dev An ERC20 token owned by another contract, which has minting permissions and can use transferFrom to receive
+ * anyone's tokens. This contract is an internal helper for GSNRecipientERC20Fee, and should not be used
+ * outside of this context.
+ */
+// solhint-disable-next-line contract-name-camelcase
+contract __unstable__ERC20PrimaryAdmin is ERC20, ERC20Detailed, Secondary {
+    uint256 private constant UINT256_MAX = 2**256 - 1;
+
+    constructor(string memory name, string memory symbol, uint8 decimals) public {
+        Secondary.initialize(msg.sender);
+        ERC20Detailed.initialize(name, symbol, decimals);
+    }
+
+    // The primary account (GSNRecipientERC20Fee) can mint tokens
+    function mint(address account, uint256 amount) public onlyPrimary {
+        _mint(account, amount);
+    }
+
+    // The primary account has 'infinite' allowance for all token holders
+    function allowance(address owner, address spender) public view returns (uint256) {
+        if (spender == primary()) {
+            return UINT256_MAX;
+        } else {
+            return super.allowance(owner, spender);
+        }
+    }
+
+    // Allowance for the primary account cannot be changed (it is always 'infinite')
+    function _approve(address owner, address spender, uint256 value) internal {
+        if (spender == primary()) {
+            return;
+        } else {
+            super._approve(owner, spender, value);
+        }
+    }
+
+    function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
+        if (recipient == primary()) {
+            _transfer(sender, recipient, amount);
+            return true;
+        } else {
+            return super.transferFrom(sender, recipient, amount);
+        }
+    }
+}

contracts/GSN/bouncers/GSNBouncerSignature.sol

@@ -0,0 +1,70 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "./GSNBouncerBase.sol";
+import "../../cryptography/ECDSA.sol";
+
+contract GSNBouncerSignature is Initializable, GSNBouncerBase {
+    using ECDSA for bytes32;
+
+    // We use a random storage slot to allow proxy contracts to enable GSN support in an upgrade without changing their
+    // storage layout. This value is calculated as: keccak256('gsn.bouncer.signature.trustedSigner'), minus 1.
+    bytes32 constant private TRUSTED_SIGNER_STORAGE_SLOT = 0xe7b237a4017a399d277819456dce32c2356236bbc518a6d84a9a8d1cfdf1e9c5;
+
+    enum GSNBouncerSignatureErrorCodes {
+        INVALID_SIGNER
+    }
+
+    function initialize(address trustedSigner) public initializer {
+        _setTrustedSigner(trustedSigner);
+    }
+
+    function acceptRelayedCall(
+        address relay,
+        address from,
+        bytes calldata encodedFunction,
+        uint256 transactionFee,
+        uint256 gasPrice,
+        uint256 gasLimit,
+        uint256 nonce,
+        bytes calldata approvalData,
+        uint256
+    )
+        external
+        view
+        returns (uint256, bytes memory)
+    {
+        bytes memory blob = abi.encodePacked(
+            relay,
+            from,
+            encodedFunction,
+            transactionFee,
+            gasPrice,
+            gasLimit,
+            nonce, // Prevents replays on RelayHub
+            getHubAddr(), // Prevents replays in multiple RelayHubs
+            address(this) // Prevents replays in multiple recipients
+        );
+        if (keccak256(blob).toEthSignedMessageHash().recover(approvalData) == _getTrustedSigner()) {
+            return _approveRelayedCall();
+        } else {
+            return _rejectRelayedCall(uint256(GSNBouncerSignatureErrorCodes.INVALID_SIGNER));
+        }
+    }
+
+    function _getTrustedSigner() private view returns (address trustedSigner) {
+      bytes32 slot = TRUSTED_SIGNER_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        trustedSigner := sload(slot)
+      }
+    }
+
+    function _setTrustedSigner(address trustedSigner) private {
+      bytes32 slot = TRUSTED_SIGNER_STORAGE_SLOT;
+      // solhint-disable-next-line no-inline-assembly
+      assembly {
+        sstore(slot, trustedSigner)
+      }
+    }
+}

contracts/access/roles/CapperRole.sol

@@ -1,8 +1,11 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../../GSN/Context.sol";
 import "../Roles.sol";
 
-contract CapperRole {
+contract CapperRole is Initializable, Context {
     using Roles for Roles.Role;
 
     event CapperAdded(address indexed account);
@@ -10,12 +13,14 @@ contract CapperRole {
 
     Roles.Role private _cappers;
 
-    constructor () internal {
-        _addCapper(msg.sender);
+    function initialize(address sender) public initializer {
+        if (!isCapper(sender)) {
+            _addCapper(sender);
+        }
     }
 
     modifier onlyCapper() {
-        require(isCapper(msg.sender));
+        require(isCapper(_msgSender()), "CapperRole: caller does not have the Capper role");
         _;
     }
 
@@ -28,7 +33,7 @@ contract CapperRole {
     }
 
     function renounceCapper() public {
-        _removeCapper(msg.sender);
+        _removeCapper(_msgSender());
     }
 
     function _addCapper(address account) internal {
@@ -40,4 +45,6 @@ contract CapperRole {
         _cappers.remove(account);
         emit CapperRemoved(account);
     }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/MinterRole.sol

@@ -1,8 +1,11 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../../GSN/Context.sol";
 import "../Roles.sol";
 
-contract MinterRole {
+contract MinterRole is Initializable, Context {
     using Roles for Roles.Role;
 
     event MinterAdded(address indexed account);
@@ -10,12 +13,14 @@ contract MinterRole {
 
     Roles.Role private _minters;
 
-    constructor () internal {
-        _addMinter(msg.sender);
+    function initialize(address sender) public initializer {
+        if (!isMinter(sender)) {
+            _addMinter(sender);
+        }
     }
 
     modifier onlyMinter() {
-        require(isMinter(msg.sender));
+        require(isMinter(_msgSender()), "MinterRole: caller does not have the Minter role");
         _;
     }
 
@@ -28,7 +33,7 @@ contract MinterRole {
     }
 
     function renounceMinter() public {
-        _removeMinter(msg.sender);
+        _removeMinter(_msgSender());
     }
 
     function _addMinter(address account) internal {
@@ -40,4 +45,6 @@ contract MinterRole {
         _minters.remove(account);
         emit MinterRemoved(account);
     }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/PauserRole.sol

@@ -1,8 +1,11 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../../GSN/Context.sol";
 import "../Roles.sol";
 
-contract PauserRole {
+contract PauserRole is Initializable, Context {
     using Roles for Roles.Role;
 
     event PauserAdded(address indexed account);
@@ -10,12 +13,14 @@ contract PauserRole {
 
     Roles.Role private _pausers;
 
-    constructor () internal {
-        _addPauser(msg.sender);
+    function initialize(address sender) public initializer {
+        if (!isPauser(sender)) {
+            _addPauser(sender);
+        }
     }
 
     modifier onlyPauser() {
-        require(isPauser(msg.sender));
+        require(isPauser(_msgSender()), "PauserRole: caller does not have the Pauser role");
         _;
     }
 
@@ -28,7 +33,7 @@ contract PauserRole {
     }
 
     function renouncePauser() public {
-        _removePauser(msg.sender);
+        _removePauser(_msgSender());
     }
 
     function _addPauser(address account) internal {
@@ -40,4 +45,6 @@ contract PauserRole {
         _pausers.remove(account);
         emit PauserRemoved(account);
     }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/SignerRole.sol

@@ -1,8 +1,11 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../../GSN/Context.sol";
 import "../Roles.sol";
 
-contract SignerRole {
+contract SignerRole is Initializable, Context {
     using Roles for Roles.Role;
 
     event SignerAdded(address indexed account);
@@ -10,12 +13,14 @@ contract SignerRole {
 
     Roles.Role private _signers;
 
-    constructor () internal {
-        _addSigner(msg.sender);
+    function initialize(address sender) public initializer {
+        if (!isSigner(sender)) {
+            _addSigner(sender);
+        }
     }
 
     modifier onlySigner() {
-        require(isSigner(msg.sender));
+        require(isSigner(_msgSender()), "SignerRole: caller does not have the Signer role");
         _;
     }
 
@@ -28,7 +33,7 @@ contract SignerRole {
     }
 
     function renounceSigner() public {
-        _removeSigner(msg.sender);
+        _removeSigner(_msgSender());
     }
 
     function _addSigner(address account) internal {
@@ -40,4 +45,6 @@ contract SignerRole {
         _signers.remove(account);
         emit SignerRemoved(account);
     }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/WhitelistAdminRole.sol

@@ -1,12 +1,15 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../../GSN/Context.sol";
 import "../Roles.sol";
 
 /**
  * @title WhitelistAdminRole
  * @dev WhitelistAdmins are responsible for assigning and removing Whitelisted accounts.
  */
-contract WhitelistAdminRole {
+contract WhitelistAdminRole is Initializable, Context {
     using Roles for Roles.Role;
 
     event WhitelistAdminAdded(address indexed account);
@@ -14,12 +17,14 @@ contract WhitelistAdminRole {
 
     Roles.Role private _whitelistAdmins;
 
-    constructor () internal {
-        _addWhitelistAdmin(msg.sender);
+    function initialize(address sender) public initializer {
+        if (!isWhitelistAdmin(sender)) {
+            _addWhitelistAdmin(sender);
+        }
     }
 
     modifier onlyWhitelistAdmin() {
-        require(isWhitelistAdmin(msg.sender));
+        require(isWhitelistAdmin(_msgSender()), "WhitelistAdminRole: caller does not have the WhitelistAdmin role");
         _;
     }
 
@@ -32,7 +37,7 @@ contract WhitelistAdminRole {
     }
 
     function renounceWhitelistAdmin() public {
-        _removeWhitelistAdmin(msg.sender);
+        _removeWhitelistAdmin(_msgSender());
     }
 
     function _addWhitelistAdmin(address account) internal {
@@ -44,4 +49,6 @@ contract WhitelistAdminRole {
         _whitelistAdmins.remove(account);
         emit WhitelistAdminRemoved(account);
     }
+
+    uint256[50] private ______gap;
 }

contracts/access/roles/WhitelistedRole.sol

@@ -1,5 +1,8 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../../GSN/Context.sol";
 import "../Roles.sol";
 import "./WhitelistAdminRole.sol";
 
@@ -9,7 +12,7 @@ import "./WhitelistAdminRole.sol";
  * crowdsale). This role is special in that the only accounts that can add it are WhitelistAdmins (who can also remove
  * it), and not Whitelisteds themselves.
  */
-contract WhitelistedRole is WhitelistAdminRole {
+contract WhitelistedRole is Initializable, Context, WhitelistAdminRole {
     using Roles for Roles.Role;
 
     event WhitelistedAdded(address indexed account);
@@ -18,10 +21,14 @@ contract WhitelistedRole is WhitelistAdminRole {
     Roles.Role private _whitelisteds;
 
     modifier onlyWhitelisted() {
-        require(isWhitelisted(msg.sender));
+        require(isWhitelisted(_msgSender()), "WhitelistedRole: caller does not have the Whitelisted role");
         _;
     }
 
+    function initialize(address sender) public initializer {
+        WhitelistAdminRole.initialize(sender);
+    }
+
     function isWhitelisted(address account) public view returns (bool) {
         return _whitelisteds.has(account);
     }
@@ -35,7 +42,7 @@ contract WhitelistedRole is WhitelistAdminRole {
     }
 
     function renounceWhitelisted() public {
-        _removeWhitelisted(msg.sender);
+        _removeWhitelisted(_msgSender());
     }
 
     function _addWhitelisted(address account) internal {
@@ -47,4 +54,6 @@ contract WhitelistedRole is WhitelistAdminRole {
         _whitelisteds.remove(account);
         emit WhitelistedRemoved(account);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/Crowdsale.sol

@@ -1,5 +1,8 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../GSN/Context.sol";
 import "../token/ERC20/IERC20.sol";
 import "../math/SafeMath.sol";
 import "../token/ERC20/SafeERC20.sol";
@@ -17,7 +20,7 @@ import "../utils/ReentrancyGuard.sol";
  * the methods to add functionality. Consider using 'super' where appropriate to concatenate
  * behavior.
  */
-contract Crowdsale is ReentrancyGuard {
+contract Crowdsale is Initializable, Context, ReentrancyGuard {
     using SafeMath for uint256;
     using SafeERC20 for IERC20;
 
@@ -53,7 +56,7 @@ contract Crowdsale is ReentrancyGuard {
      * @param wallet Address where collected funds will be forwarded to
      * @param token Address of the token being sold
      */
-    constructor (uint256 rate, address payable wallet, IERC20 token) public {
+    function initialize(uint256 rate, address payable wallet, IERC20 token) public initializer {
         require(rate > 0);
         require(wallet != address(0));
         require(address(token) != address(0));
@@ -70,7 +73,7 @@ contract Crowdsale is ReentrancyGuard {
      * buyTokens directly when purchasing tokens from a contract.
      */
     function () external payable {
-        buyTokens(msg.sender);
+        buyTokens(_msgSender());
     }
 
     /**
@@ -118,7 +121,7 @@ contract Crowdsale is ReentrancyGuard {
         _weiRaised = _weiRaised.add(weiAmount);
 
         _processPurchase(beneficiary, tokens);
-        emit TokensPurchased(msg.sender, beneficiary, weiAmount, tokens);
+        emit TokensPurchased(_msgSender(), beneficiary, weiAmount, tokens);
 
         _updatePurchasingState(beneficiary, weiAmount);
 
@@ -126,6 +129,10 @@ contract Crowdsale is ReentrancyGuard {
         _postValidatePurchase(beneficiary, weiAmount);
     }
 
+    function _hasBeenInitialized() internal view returns (bool) {
+        return ((_rate > 0) && (_wallet != address(0)) && (address(_token) != address(0)));
+    }
+
     /**
      * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
      * Use `super` in contracts that inherit from Crowdsale to extend their validations.
@@ -195,4 +202,6 @@ contract Crowdsale is ReentrancyGuard {
     function _forwardFunds() internal {
         _wallet.transfer(msg.value);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/FinalizableCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../validation/TimedCrowdsale.sol";
 
@@ -8,17 +9,13 @@ import "../validation/TimedCrowdsale.sol";
  * @dev Extension of TimedCrowdsale with a one-off finalization action, where one
  * can do extra work after finishing.
  */
-contract FinalizableCrowdsale is TimedCrowdsale {
+contract FinalizableCrowdsale is Initializable, TimedCrowdsale {
     using SafeMath for uint256;
 
     bool private _finalized;
 
     event CrowdsaleFinalized();
 
-    constructor () internal {
-        _finalized = false;
-    }
-
     /**
      * @return true if the crowdsale is finalized, false otherwise.
      */
@@ -48,4 +45,6 @@ contract FinalizableCrowdsale is TimedCrowdsale {
     function _finalization() internal {
         // solhint-disable-previous-line no-empty-blocks
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/PostDeliveryCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";
 
@@ -7,7 +8,7 @@ import "../../math/SafeMath.sol";
  * @title PostDeliveryCrowdsale
  * @dev Crowdsale that locks tokens from withdrawal until it ends.
  */
-contract PostDeliveryCrowdsale is TimedCrowdsale {
+contract PostDeliveryCrowdsale is Initializable, TimedCrowdsale {
     using SafeMath for uint256;
 
     mapping(address => uint256) private _balances;
@@ -40,4 +41,5 @@ contract PostDeliveryCrowdsale is TimedCrowdsale {
         _balances[beneficiary] = _balances[beneficiary].add(tokenAmount);
     }
 
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/RefundableCrowdsale.sol

@@ -1,5 +1,8 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../../GSN/Context.sol";
 import "../../math/SafeMath.sol";
 import "./FinalizableCrowdsale.sol";
 import "../../payment/escrow/RefundEscrow.sol";
@@ -14,7 +17,7 @@ import "../../payment/escrow/RefundEscrow.sol";
  * the goal is unlikely to be met, they sell their tokens (possibly at a discount). The attacker will be refunded when
  * the crowdsale is finalized, and the users that purchased from them will be left with worthless tokens.
  */
-contract RefundableCrowdsale is FinalizableCrowdsale {
+contract RefundableCrowdsale is Initializable, Context, FinalizableCrowdsale {
     using SafeMath for uint256;
 
     // minimum amount of funds to be raised in weis
@@ -27,9 +30,16 @@ contract RefundableCrowdsale is FinalizableCrowdsale {
      * @dev Constructor, creates RefundEscrow.
      * @param goal Funding goal
      */
-    constructor (uint256 goal) public {
+    function initialize(uint256 goal) public initializer {
+        // FinalizableCrowdsale depends on TimedCrowdsale
+        assert(TimedCrowdsale._hasBeenInitialized());
+
         require(goal > 0);
-        _escrow = new RefundEscrow(wallet());
+        // conditional added to make initializer idempotent in case of diamond inheritance
+        if (address(_escrow) == address(0)) {
+            _escrow = new RefundEscrow();
+            _escrow.initialize(wallet(), address(this));
+        }
         _goal = goal;
     }
 
@@ -77,6 +87,8 @@ contract RefundableCrowdsale is FinalizableCrowdsale {
      * @dev Overrides Crowdsale fund forwarding, sending funds to escrow.
      */
     function _forwardFunds() internal {
-        _escrow.deposit.value(msg.value)(msg.sender);
+        _escrow.deposit.value(msg.value)(_msgSender());
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/distribution/RefundablePostDeliveryCrowdsale.sol

@@ -1,20 +1,23 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
 import "./RefundableCrowdsale.sol";
 import "./PostDeliveryCrowdsale.sol";
 
-
 /**
  * @title RefundablePostDeliveryCrowdsale
  * @dev Extension of RefundableCrowdsale contract that only delivers the tokens
  * once the crowdsale has closed and the goal met, preventing refunds to be issued
  * to token holders.
  */
-contract RefundablePostDeliveryCrowdsale is RefundableCrowdsale, PostDeliveryCrowdsale {
+contract RefundablePostDeliveryCrowdsale is Initializable, RefundableCrowdsale, PostDeliveryCrowdsale {
     function withdrawTokens(address beneficiary) public {
         require(finalized());
         require(goalReached());
 
         super.withdrawTokens(beneficiary);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/emission/AllowanceCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Crowdsale.sol";
 import "../../token/ERC20/IERC20.sol";
 import "../../token/ERC20/SafeERC20.sol";
@@ -10,7 +11,7 @@ import "../../math/Math.sol";
  * @title AllowanceCrowdsale
  * @dev Extension of Crowdsale where tokens are held by a wallet, which approves an allowance to the crowdsale.
  */
-contract AllowanceCrowdsale is Crowdsale {
+contract AllowanceCrowdsale is Initializable, Crowdsale {
     using SafeMath for uint256;
     using SafeERC20 for IERC20;
 
@@ -20,7 +21,9 @@ contract AllowanceCrowdsale is Crowdsale {
      * @dev Constructor, takes token wallet address.
      * @param tokenWallet Address holding the tokens, which has approved allowance to the crowdsale
      */
-    constructor (address tokenWallet) public {
+    function initialize(address tokenWallet) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
+
         require(tokenWallet != address(0));
         _tokenWallet = tokenWallet;
     }
@@ -48,4 +51,6 @@ contract AllowanceCrowdsale is Crowdsale {
     function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
         token().safeTransferFrom(_tokenWallet, beneficiary, tokenAmount);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/emission/MintedCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../Crowdsale.sol";
 import "../../token/ERC20/ERC20Mintable.sol";
 
@@ -8,7 +9,7 @@ import "../../token/ERC20/ERC20Mintable.sol";
  * @dev Extension of Crowdsale contract whose tokens are minted in each purchase.
  * Token ownership should be transferred to MintedCrowdsale for minting.
  */
-contract MintedCrowdsale is Crowdsale {
+contract MintedCrowdsale is Initializable, Crowdsale {
     /**
      * @dev Overrides delivery by minting tokens upon purchase.
      * @param beneficiary Token purchaser
@@ -18,4 +19,6 @@ contract MintedCrowdsale is Crowdsale {
         // Potentially dangerous assumption about the type of the token.
         require(ERC20Mintable(address(token())).mint(beneficiary, tokenAmount));
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/price/IncreasingPriceCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../validation/TimedCrowdsale.sol";
 import "../../math/SafeMath.sol";
 
@@ -9,7 +10,7 @@ import "../../math/SafeMath.sol";
  * Note that what should be provided to the constructor is the initial and final _rates_, that is,
  * the amount of tokens per wei contributed. Thus, the initial rate must be greater than the final rate.
  */
-contract IncreasingPriceCrowdsale is TimedCrowdsale {
+contract IncreasingPriceCrowdsale is Initializable, TimedCrowdsale {
     using SafeMath for uint256;
 
     uint256 private _initialRate;
@@ -20,7 +21,9 @@ contract IncreasingPriceCrowdsale is TimedCrowdsale {
      * @param initialRate Number of tokens a buyer gets per wei at the start of the crowdsale
      * @param finalRate Number of tokens a buyer gets per wei at the end of the crowdsale
      */
-    constructor (uint256 initialRate, uint256 finalRate) public {
+    function initialize(uint256 initialRate, uint256 finalRate) public initializer {
+        assert(TimedCrowdsale._hasBeenInitialized());
+
         require(finalRate > 0);
         require(initialRate > finalRate);
         _initialRate = initialRate;
@@ -75,4 +78,6 @@ contract IncreasingPriceCrowdsale is TimedCrowdsale {
         uint256 currentRate = getCurrentRate();
         return currentRate.mul(weiAmount);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/CappedCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
 
@@ -7,7 +8,7 @@ import "../Crowdsale.sol";
  * @title CappedCrowdsale
  * @dev Crowdsale with a limit for total contributions.
  */
-contract CappedCrowdsale is Crowdsale {
+contract CappedCrowdsale is Initializable, Crowdsale {
     using SafeMath for uint256;
 
     uint256 private _cap;
@@ -16,7 +17,9 @@ contract CappedCrowdsale is Crowdsale {
      * @dev Constructor, takes maximum amount of wei accepted in the crowdsale.
      * @param cap Max amount of wei to be contributed
      */
-    constructor (uint256 cap) public {
+    function initialize(uint256 cap) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
+
         require(cap > 0);
         _cap = cap;
     }
@@ -45,4 +48,6 @@ contract CappedCrowdsale is Crowdsale {
         super._preValidatePurchase(beneficiary, weiAmount);
         require(weiRaised().add(weiAmount) <= _cap);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/IndividuallyCappedCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
 import "../../access/roles/CapperRole.sol";
@@ -8,12 +9,18 @@ import "../../access/roles/CapperRole.sol";
  * @title IndividuallyCappedCrowdsale
  * @dev Crowdsale with per-beneficiary caps.
  */
-contract IndividuallyCappedCrowdsale is Crowdsale, CapperRole {
+contract IndividuallyCappedCrowdsale is Initializable, Crowdsale, CapperRole {
     using SafeMath for uint256;
 
     mapping(address => uint256) private _contributions;
     mapping(address => uint256) private _caps;
 
+    function initialize(address sender) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
+
+        CapperRole.initialize(sender);
+    }
+
     /**
      * @dev Sets a specific beneficiary's maximum contribution.
      * @param beneficiary Address to be capped
@@ -60,4 +67,6 @@ contract IndividuallyCappedCrowdsale is Crowdsale, CapperRole {
         super._updatePurchasingState(beneficiary, weiAmount);
         _contributions[beneficiary] = _contributions[beneficiary].add(weiAmount);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/PausableCrowdsale.sol

@@ -1,5 +1,7 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
 import "../Crowdsale.sol";
 import "../../lifecycle/Pausable.sol";
 
@@ -7,7 +9,13 @@ import "../../lifecycle/Pausable.sol";
  * @title PausableCrowdsale
  * @dev Extension of Crowdsale contract where purchases can be paused and unpaused by the pauser role.
  */
-contract PausableCrowdsale is Crowdsale, Pausable {
+contract PausableCrowdsale is Initializable, Crowdsale, Pausable {
+    function initialize(address sender) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
+
+        Pausable.initialize(sender);
+    }
+
     /**
      * @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
      * Use super to concatenate validations.
@@ -18,4 +26,6 @@ contract PausableCrowdsale is Crowdsale, Pausable {
     function _preValidatePurchase(address _beneficiary, uint256 _weiAmount) internal view whenNotPaused {
         return super._preValidatePurchase(_beneficiary, _weiAmount);
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/TimedCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../math/SafeMath.sol";
 import "../Crowdsale.sol";
 
@@ -7,7 +8,7 @@ import "../Crowdsale.sol";
  * @title TimedCrowdsale
  * @dev Crowdsale accepting contributions only within a time frame.
  */
-contract TimedCrowdsale is Crowdsale {
+contract TimedCrowdsale is Initializable, Crowdsale {
     using SafeMath for uint256;
 
     uint256 private _openingTime;
@@ -33,7 +34,9 @@ contract TimedCrowdsale is Crowdsale {
      * @param openingTime Crowdsale opening time
      * @param closingTime Crowdsale closing time
      */
-    constructor (uint256 openingTime, uint256 closingTime) public {
+    function initialize(uint256 openingTime, uint256 closingTime) public initializer {
+        assert(Crowdsale._hasBeenInitialized());
+
         // solhint-disable-next-line not-rely-on-time
         require(openingTime >= block.timestamp);
         require(closingTime > openingTime);
@@ -73,6 +76,10 @@ contract TimedCrowdsale is Crowdsale {
         return block.timestamp > _closingTime;
     }
 
+    function _hasBeenInitialized() internal view returns (bool) {
+        return ((_openingTime > 0) && (_closingTime > 0));
+    }
+
     /**
      * @dev Extend parent behavior requiring to be within contributing period
      * @param beneficiary Token purchaser
@@ -93,4 +100,6 @@ contract TimedCrowdsale is Crowdsale {
         emit TimedCrowdsaleExtended(_closingTime, newClosingTime);
         _closingTime = newClosingTime;
     }
+
+    uint256[50] private ______gap;
 }

contracts/crowdsale/validation/WhitelistCrowdsale.sol

@@ -7,7 +7,13 @@ import "../../access/roles/WhitelistedRole.sol";
  * @title WhitelistCrowdsale
  * @dev Crowdsale in which only whitelisted users can contribute.
  */
-contract WhitelistCrowdsale is WhitelistedRole, Crowdsale {
+contract WhitelistCrowdsale is Initializable, WhitelistedRole, Crowdsale {
+    function initialize(address sender) public initializer {
+        WhitelistedRole.initialize(sender);
+
+        assert(Crowdsale._hasBeenInitialized());
+    }
+
     /**
      * @dev Extend parent behavior requiring beneficiary to be whitelisted. Note that no
      * restriction is imposed on the account sending the transaction.
@@ -18,4 +24,6 @@ contract WhitelistCrowdsale is WhitelistedRole, Crowdsale {
         require(isWhitelisted(_beneficiary));
         super._preValidatePurchase(_beneficiary, _weiAmount);
     }
+
+    uint256[50] private ______gap;
 }

contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../../token/ERC20/IERC20.sol";
 
 /**
@@ -7,10 +8,10 @@ import "../../token/ERC20/IERC20.sol";
  * @dev See https://eips.ethereum.org/EIPS/eip-1046
  * @dev tokenURI must respond with a URI that implements https://eips.ethereum.org/EIPS/eip-1047
  */
-contract ERC20Metadata {
+contract ERC20Metadata is Initializable {
     string private _tokenURI;
 
-    constructor (string memory tokenURI_) public {
+    function initialize(string memory tokenURI_) public {
         _setTokenURI(tokenURI_);
     }
 
@@ -21,4 +22,6 @@ contract ERC20Metadata {
     function _setTokenURI(string memory tokenURI_) internal {
         _tokenURI = tokenURI_;
     }
+
+    uint256[50] private ______gap;
 }

contracts/drafts/ERC20Migrator.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../token/ERC20/IERC20.sol";
 import "../token/ERC20/ERC20Mintable.sol";
 import "../token/ERC20/SafeERC20.sol";
@@ -21,9 +22,9 @@ import "../math/Math.sol";
  * is migrated, and remain there forever.
  * Although this contract can be used in many different scenarios, the main
  * motivation was to provide a way to migrate ERC20 tokens into an upgradeable
- * version of it using ZeppelinOS. To read more about how this can be done
+ * version of it using the OpenZeppelin SDK. To read more about how this can be done
  * using this implementation, please follow the official documentation site of
- * ZeppelinOS: https://docs.zeppelinos.org/docs/erc20_onboarding.html
+ * the OpenZeppelinSDK: https://docs.zeppelinos.org/docs/erc20_onboarding.html
  * Example of usage:
  * ```
  * const migrator = await ERC20Migrator.new(legacyToken.address);
@@ -31,7 +32,7 @@ import "../math/Math.sol";
  * await migrator.beginMigration(newToken.address);
  * ```
  */
-contract ERC20Migrator {
+contract ERC20Migrator is Initializable {
     using SafeERC20 for IERC20;
 
     /// Address of the old token contract
@@ -43,7 +44,7 @@ contract ERC20Migrator {
     /**
      * @param legacyToken address of the old token contract
      */
-    constructor (IERC20 legacyToken) public {
+    function initialize(IERC20 legacyToken) public initializer {
         require(address(legacyToken) != address(0));
         _legacyToken = legacyToken;
     }
@@ -98,4 +99,6 @@ contract ERC20Migrator {
         uint256 amount = Math.min(balance, allowance);
         migrate(account, amount);
     }
+
+    uint256[50] private ______gap;
 }

contracts/drafts/ERC20Snapshot.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../math/SafeMath.sol";
 import "../utils/Arrays.sol";
 import "../drafts/Counters.sol";
@@ -18,7 +19,7 @@ import "../token/ERC20/ERC20.sol";
  * account address.
  * @author Validity Labs AG <info@validitylabs.org>
  */
-contract ERC20Snapshot is ERC20 {
+contract ERC20Snapshot is Initializable, ERC20 {
     using SafeMath for uint256;
     using Arrays for uint256[];
     using Counters for Counters.Counter;
@@ -136,4 +137,6 @@ contract ERC20Snapshot is ERC20 {
             return ids[ids.length - 1];
         }
     }
+
+    uint256[50] private ______gap;
 }

contracts/drafts/SignatureBouncer.sol

@@ -1,5 +1,8 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../GSN/Context.sol";
 import "../access/roles/SignerRole.sol";
 import "../cryptography/ECDSA.sol";
 
@@ -34,7 +37,7 @@ import "../cryptography/ECDSA.sol";
  * the data in the signature much more complex.
  * See https://ethereum.stackexchange.com/a/50616 for more details.
  */
-contract SignatureBouncer is SignerRole {
+contract SignatureBouncer is Initializable, Context, SignerRole {
     using ECDSA for bytes32;
 
     // Function selectors are 4 bytes long, as documented in
@@ -43,15 +46,15 @@ contract SignatureBouncer is SignerRole {
     // Signature size is 65 bytes (tightly packed v + r + s), but gets padded to 96 bytes
     uint256 private constant _SIGNATURE_SIZE = 96;
 
-    constructor () internal {
-        // solhint-disable-previous-line no-empty-blocks
+    function initialize(address sender) public initializer {
+        SignerRole.initialize(sender);
     }
 
     /**
      * @dev requires that a valid signature of a signer was provided
      */
     modifier onlyValidSignature(bytes memory signature) {
-        require(_isValidSignature(msg.sender, signature));
+        require(_isValidSignature(_msgSender(), signature), "SignatureBouncer: invalid signature for caller");
         _;
     }
 
@@ -59,7 +62,8 @@ contract SignatureBouncer is SignerRole {
      * @dev requires that a valid signature with a specified method of a signer was provided
      */
     modifier onlyValidSignatureAndMethod(bytes memory signature) {
-        require(_isValidSignatureAndMethod(msg.sender, signature));
+        // solhint-disable-next-line max-line-length
+        require(_isValidSignatureAndMethod(_msgSender(), signature), "SignatureBouncer: invalid signature for caller and method");
         _;
     }
 
@@ -67,7 +71,8 @@ contract SignatureBouncer is SignerRole {
      * @dev requires that a valid signature with a specified method and params of a signer was provided
      */
     modifier onlyValidSignatureAndData(bytes memory signature) {
-        require(_isValidSignatureAndData(msg.sender, signature));
+        // solhint-disable-next-line max-line-length
+        require(_isValidSignatureAndData(_msgSender(), signature), "SignatureBouncer: invalid signature for caller and data");
         _;
     }
 
@@ -84,9 +89,10 @@ contract SignatureBouncer is SignerRole {
      * @return bool
      */
     function _isValidSignatureAndMethod(address account, bytes memory signature) internal view returns (bool) {
+        bytes memory msgData = _msgData();
         bytes memory data = new bytes(_METHOD_ID_SIZE);
-        for (uint i = 0; i < data.length; i++) {
-            data[i] = msg.data[i];
+        for (uint256 i = 0; i < data.length; i++) {
+            data[i] = msgData[i];
         }
         return _isValidDataHash(keccak256(abi.encodePacked(address(this), account, data)), signature);
     }
@@ -97,11 +103,12 @@ contract SignatureBouncer is SignerRole {
      * @return bool
      */
     function _isValidSignatureAndData(address account, bytes memory signature) internal view returns (bool) {
-        require(msg.data.length > _SIGNATURE_SIZE);
+        bytes memory msgData = _msgData();
+        require(msgData.length > _SIGNATURE_SIZE, "SignatureBouncer: data is too short");
 
-        bytes memory data = new bytes(msg.data.length - _SIGNATURE_SIZE);
-        for (uint i = 0; i < data.length; i++) {
-            data[i] = msg.data[i];
+        bytes memory data = new bytes(msgData.length - _SIGNATURE_SIZE);
+        for (uint256 i = 0; i < data.length; i++) {
+            data[i] = msgData[i];
         }
 
         return _isValidDataHash(keccak256(abi.encodePacked(address(this), account, data)), signature);
@@ -117,4 +124,6 @@ contract SignatureBouncer is SignerRole {
 
         return signer != address(0) && isSigner(signer);
     }
+
+    uint256[50] private ______gap;
 }

contracts/drafts/TokenVesting.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../token/ERC20/SafeERC20.sol";
 import "../ownership/Ownable.sol";
 import "../math/SafeMath.sol";
@@ -10,7 +11,7 @@ import "../math/SafeMath.sol";
  * typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
  * owner.
  */
-contract TokenVesting is Ownable {
+contract TokenVesting is Initializable, Ownable {
     // The vesting schedule is time-based (i.e. using block timestamps as opposed to e.g. block numbers), and is
     // therefore sensitive to timestamp manipulation (which is something miners can do, to a certain degree). Therefore,
     // it is recommended to avoid using short time durations (less than a minute). Typical vesting schemes, with a
@@ -46,7 +47,9 @@ contract TokenVesting is Ownable {
      * @param duration duration in seconds of the period in which the tokens will vest
      * @param revocable whether the vesting is revocable or not
      */
-    constructor (address beneficiary, uint256 start, uint256 cliffDuration, uint256 duration, bool revocable) public {
+    function initialize(address beneficiary, uint256 start, uint256 cliffDuration, uint256 duration, bool revocable, address sender) public initializer {
+        Ownable.initialize(sender);
+
         require(beneficiary != address(0));
         require(cliffDuration <= duration);
         require(duration > 0);
@@ -169,4 +172,6 @@ contract TokenVesting is Ownable {
             return totalBalance.mul(block.timestamp.sub(_start)).div(_duration);
         }
     }
+
+    uint256[50] private ______gap;
 }

contracts/examples/SampleCrowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "../crowdsale/validation/CappedCrowdsale.sol";
 import "../crowdsale/distribution/RefundableCrowdsale.sol";
 import "../crowdsale/emission/MintedCrowdsale.sol";
@@ -11,10 +12,13 @@ import "../token/ERC20/ERC20Detailed.sol";
  * @dev Very simple ERC20 Token that can be minted.
  * It is meant to be used in a crowdsale contract.
  */
-contract SampleCrowdsaleToken is ERC20Mintable, ERC20Detailed {
-    constructor () public ERC20Detailed("Sample Crowdsale Token", "SCT", 18) {
-        // solhint-disable-previous-line no-empty-blocks
+contract SampleCrowdsaleToken is Initializable, ERC20Mintable, ERC20Detailed {
+    function initialize(address sender) public initializer {
+        ERC20Mintable.initialize(sender);
+        ERC20Detailed.initialize("Sample Crowdsale Token", "SCT", 18);
     }
+
+    uint256[50] private ______gap;
 }
 
 /**
@@ -30,8 +34,9 @@ contract SampleCrowdsaleToken is ERC20Mintable, ERC20Detailed {
  * After adding multiple features it's good practice to run integration tests
  * to ensure that subcontracts works together as intended.
  */
-contract SampleCrowdsale is CappedCrowdsale, RefundableCrowdsale, MintedCrowdsale {
-    constructor (
+contract SampleCrowdsale is Initializable, Crowdsale, CappedCrowdsale, RefundableCrowdsale, MintedCrowdsale {
+
+    function initialize(
         uint256 openingTime,
         uint256 closingTime,
         uint256 rate,
@@ -41,13 +46,17 @@ contract SampleCrowdsale is CappedCrowdsale, RefundableCrowdsale, MintedCrowdsal
         uint256 goal
     )
         public
-        Crowdsale(rate, wallet, token)
-        CappedCrowdsale(cap)
-        TimedCrowdsale(openingTime, closingTime)
-        RefundableCrowdsale(goal)
+        initializer
     {
+        Crowdsale.initialize(rate, wallet, token);
+        CappedCrowdsale.initialize(cap);
+        TimedCrowdsale.initialize(openingTime, closingTime);
+        RefundableCrowdsale.initialize(goal);
+
         //As goal needs to be met for a successful crowdsale
         //the value needs to less or equal than a cap which is limit for accepted funds
         require(goal <= cap);
     }
+
+    uint256[50] private ______gap;
 }

contracts/examples/SimpleToken.sol

@@ -1,5 +1,8 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../GSN/Context.sol";
 import "../token/ERC20/ERC20.sol";
 import "../token/ERC20/ERC20Detailed.sol";
 
@@ -9,14 +12,15 @@ import "../token/ERC20/ERC20Detailed.sol";
  * Note they can later distribute these tokens as they wish using `transfer` and other
  * `ERC20` functions.
  */
-contract SimpleToken is ERC20, ERC20Detailed {
-    uint8 public constant DECIMALS = 18;
-    uint256 public constant INITIAL_SUPPLY = 10000 * (10 ** uint256(DECIMALS));
+contract SimpleToken is Initializable, Context,  ERC20, ERC20Detailed {
 
     /**
-     * @dev Constructor that gives msg.sender all of existing tokens.
+     * @dev Constructor that gives _msgSender() all of existing tokens.
      */
-    constructor () public ERC20Detailed("SimpleToken", "SIM", DECIMALS) {
-        _mint(msg.sender, INITIAL_SUPPLY);
+    function initialize(address sender) public initializer {
+        ERC20Detailed.initialize("SimpleToken", "SIM", 18);
+        _mint(sender, 10000 * (10 ** uint256(decimals())));
     }
+
+    uint256[50] private ______gap;
 }

contracts/introspection/ERC165.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
 import "./IERC165.sol";
 
 /**
@@ -7,7 +8,7 @@ import "./IERC165.sol";
  * @author Matt Condon (@shrugs)
  * @dev Implements ERC165 using a lookup table.
  */
-contract ERC165 is IERC165 {
+contract ERC165 is Initializable, IERC165 {
     bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
     /*
      * 0x01ffc9a7 ===
@@ -23,14 +24,14 @@ contract ERC165 is IERC165 {
      * @dev A contract implementing SupportsInterfaceWithLookup
      * implement ERC165 itself
      */
-    constructor () internal {
+    function initialize() public initializer {
         _registerInterface(_INTERFACE_ID_ERC165);
     }
 
     /**
      * @dev implement supportsInterface(bytes4) using a lookup table
      */
-    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
+    function supportsInterface(bytes4 interfaceId) public view returns (bool) {
         return _supportedInterfaces[interfaceId];
     }
 
@@ -41,4 +42,6 @@ contract ERC165 is IERC165 {
         require(interfaceId != 0xffffffff);
         _supportedInterfaces[interfaceId] = true;
     }
+
+    uint256[50] private ______gap;
 }

contracts/lifecycle/Pausable.sol

@@ -1,18 +1,23 @@
 pragma solidity ^0.5.2;
 
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+
+import "../GSN/Context.sol";
 import "../access/roles/PauserRole.sol";
 
 /**
  * @title Pausable
  * @dev Base contract which allows children to implement an emergency stop mechanism.
  */
-contract Pausable is PauserRole {
+contract Pausable is Initializable, Context, PauserRole {
     event Paused(address account);
     event Unpaused(address account);
 
     bool private _paused;
 
-    constructor () internal {
+    function initialize(address sender) public initializer {
+        PauserRole.initialize(sender);
+
         _paused = false;
     }
 
@@ -44,7 +49,7 @@ contract Pausable is PauserRole {
      */
     function pause() public onlyPauser whenNotPaused {
         _paused = true;
-        emit Paused(msg.sender);
+        emit Paused(_msgSender());
     }
 
     /**
@@ -52,6 +57,8 @@ contract Pausable is PauserRole {
      */
     function unpause() public onlyPauser whenPaused {
         _paused = false;
-        emit Unpaused(msg.sender);
+        emit Unpaused(_msgSender());
     }
+
+    uint256[50] private ______gap;
 }

contracts/mocks/AllowanceCrowdsaleImpl.sol

@@ -6,9 +6,8 @@ import "../crowdsale/emission/AllowanceCrowdsale.sol";
 contract AllowanceCrowdsaleImpl is AllowanceCrowdsale {
     constructor (uint256 rate, address payable wallet, IERC20 token, address tokenWallet)
         public
-        Crowdsale(rate, wallet, token)
-        AllowanceCrowdsale(tokenWallet)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(rate, wallet, token);
+        AllowanceCrowdsale.initialize(tokenWallet);
     }
 }

contracts/mocks/CappedCrowdsaleImpl.sol

@@ -6,9 +6,8 @@ import "../crowdsale/validation/CappedCrowdsale.sol";
 contract CappedCrowdsaleImpl is CappedCrowdsale {
     constructor (uint256 rate, address payable wallet, IERC20 token, uint256 cap)
         public
-        Crowdsale(rate, wallet, token)
-        CappedCrowdsale(cap)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(rate, wallet, token);
+        CappedCrowdsale.initialize(cap);
     }
 }

contracts/mocks/CapperRoleMock.sol

@@ -3,6 +3,10 @@ pragma solidity ^0.5.2;
 import "../access/roles/CapperRole.sol";
 
 contract CapperRoleMock is CapperRole {
+    constructor() public {
+        CapperRole.initialize(_msgSender());
+    }
+
     function removeCapper(address account) public {
         _removeCapper(account);
     }

contracts/mocks/ConditionalEscrowMock.sol

@@ -6,6 +6,10 @@ import "../payment/escrow/ConditionalEscrow.sol";
 contract ConditionalEscrowMock is ConditionalEscrow {
     mapping(address => bool) private _allowed;
 
+    constructor() public {
+        ConditionalEscrow.initialize(_msgSender());
+    }
+
     function setAllowed(address payee, bool allowed) public {
         _allowed[payee] = allowed;
     }

contracts/mocks/ContextMock.sol

@@ -0,0 +1,27 @@
+pragma solidity ^0.5.0;
+
+import "../GSN/Context.sol";
+
+contract ContextMock is Context {
+    event Sender(address sender);
+
+    function msgSender() public {
+        emit Sender(_msgSender());
+    }
+
+    event Data(bytes data, uint256 integerValue, string stringValue);
+
+    function msgData(uint256 integerValue, string memory stringValue) public {
+        emit Data(_msgData(), integerValue, stringValue);
+    }
+}
+
+contract ContextMockCaller {
+    function callSender(ContextMock context) public {
+        context.msgSender();
+    }
+
+    function callData(ContextMock context, uint256 integerValue, string memory stringValue) public {
+        context.msgData(integerValue, stringValue);
+    }
+}

contracts/mocks/CrowdsaleMock.sol

@@ -3,7 +3,7 @@ pragma solidity ^0.5.2;
 import "../crowdsale/Crowdsale.sol";
 
 contract CrowdsaleMock is Crowdsale {
-    constructor (uint256 rate, address payable wallet, IERC20 token) public Crowdsale(rate, wallet, token) {
-        // solhint-disable-previous-line no-empty-blocks
+    constructor (uint256 rate, address payable wallet, IERC20 token) public {
+        Crowdsale.initialize(rate, wallet, token);
     }
 }

contracts/mocks/ERC165Mock.sol

@@ -3,6 +3,10 @@ pragma solidity ^0.5.2;
 import "../introspection/ERC165.sol";
 
 contract ERC165Mock is ERC165 {
+    constructor() public {
+        ERC165.initialize();
+    }
+
     function registerInterface(bytes4 interfaceId) public {
         _registerInterface(interfaceId);
     }

contracts/mocks/ERC20BurnableMock.sol

@@ -3,7 +3,7 @@ pragma solidity ^0.5.2;
 import "../token/ERC20/ERC20Burnable.sol";
 
 contract ERC20BurnableMock is ERC20Burnable {
-    constructor (address initialAccount, uint256 initialBalance) public {
+    constructor(address initialAccount, uint256 initialBalance) public {
         _mint(initialAccount, initialBalance);
     }
 }

contracts/mocks/ERC20CappedMock.sol

@@ -0,0 +1,13 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/ERC20Capped.sol";
+import "./MinterRoleMock.sol";
+
+
+contract ERC20CappedMock is ERC20Capped, MinterRoleMock {
+
+    constructor(uint256 cap) public {
+        ERC20Capped.initialize(cap, _msgSender());
+    }
+
+}

contracts/mocks/ERC20DetailedMock.sol

@@ -6,8 +6,7 @@ import "../token/ERC20/ERC20Detailed.sol";
 contract ERC20DetailedMock is ERC20, ERC20Detailed {
     constructor (string memory name, string memory symbol, uint8 decimals)
         public
-        ERC20Detailed(name, symbol, decimals)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        ERC20Detailed.initialize(name, symbol, decimals);
     }
 }

contracts/mocks/ERC20MetadataMock.sol

@@ -1,11 +1,11 @@
-pragma solidity ^0.5.2;
+pragma solidity ^0.5.0;
 
 import "../token/ERC20/ERC20.sol";
 import "../drafts/ERC1046/ERC20Metadata.sol";
 
 contract ERC20MetadataMock is ERC20, ERC20Metadata {
-    constructor (string memory tokenURI) public ERC20Metadata(tokenURI) {
-        // solhint-disable-previous-line no-empty-blocks
+    constructor (string memory tokenURI) public {
+        ERC20Metadata.initialize(tokenURI);
     }
 
     function setTokenURI(string memory tokenURI) public {

contracts/mocks/ERC20MigratorMock.sol

@@ -0,0 +1,12 @@
+pragma solidity ^0.5.0;
+
+import "../drafts/ERC20Migrator.sol";
+
+
+contract ERC20MigratorMock is ERC20Migrator {
+
+    constructor(IERC20 legacyToken) public {
+        ERC20Migrator.initialize(legacyToken);
+    }
+
+}

contracts/mocks/ERC20MintableMock.sol

@@ -4,5 +4,7 @@ import "../token/ERC20/ERC20Mintable.sol";
 import "./MinterRoleMock.sol";
 
 contract ERC20MintableMock is ERC20Mintable, MinterRoleMock {
-    // solhint-disable-previous-line no-empty-blocks
+    constructor() public {
+        ERC20Mintable.initialize(_msgSender());
+    }
 }

contracts/mocks/ERC20PausableMock.sol

@@ -6,6 +6,7 @@ import "./PauserRoleMock.sol";
 // mock class using ERC20Pausable
 contract ERC20PausableMock is ERC20Pausable, PauserRoleMock {
     constructor (address initialAccount, uint initialBalance) public {
+        ERC20Pausable.initialize(_msgSender());
         _mint(initialAccount, initialBalance);
     }
 }

contracts/mocks/ERC721FullMock.sol

@@ -11,8 +11,12 @@ import "../token/ERC721/ERC721Burnable.sol";
  * checking token existence, removal of a token from an address
  */
 contract ERC721FullMock is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
-    constructor (string memory name, string memory symbol) public ERC721Mintable() ERC721Full(name, symbol) {
-        // solhint-disable-previous-line no-empty-blocks
+    constructor (string memory name, string memory symbol) public {
+        ERC721.initialize();
+        ERC721Metadata.initialize(name, symbol);
+        ERC721Enumerable.initialize();
+        ERC721Mintable.initialize(_msgSender());
+        ERC721MetadataMintable.initialize(_msgSender());
     }
 
     function exists(uint256 tokenId) public view returns (bool) {

contracts/mocks/ERC721GSNRecipientMock.sol

@@ -0,0 +1,21 @@
+pragma solidity ^0.5.2;
+
+import "../token/ERC721/ERC721.sol";
+import "../GSN/GSNRecipient.sol";
+import "../GSN/bouncers/GSNBouncerSignature.sol";
+
+/**
+ * @title ERC721GSNRecipientMock
+ * A simple ERC721 mock that has GSN support enabled
+ */
+contract ERC721GSNRecipientMock is ERC721, GSNRecipient, GSNBouncerSignature {
+    constructor(address trustedSigner) public {
+        ERC721.initialize();
+        GSNRecipient.initialize();
+        GSNBouncerSignature.initialize(trustedSigner);
+    }
+
+    function mint(uint256 tokenId) public {
+        _mint(_msgSender(), tokenId);
+    }
+}

contracts/mocks/ERC721MintableBurnableImpl.sol

@@ -9,7 +9,11 @@ import "../token/ERC721/ERC721Burnable.sol";
  * @title ERC721MintableBurnableImpl
  */
 contract ERC721MintableBurnableImpl is ERC721Full, ERC721Mintable, ERC721MetadataMintable, ERC721Burnable {
-    constructor () public ERC721Mintable() ERC721Full("Test", "TEST") {
-        // solhint-disable-previous-line no-empty-blocks
+    constructor () public {
+        ERC721.initialize();
+        ERC721Metadata.initialize("Test", "TEST");
+        ERC721Enumerable.initialize();
+        ERC721Mintable.initialize(_msgSender());
+        ERC721MetadataMintable.initialize(_msgSender());
     }
 }

contracts/mocks/ERC721Mock.sol

@@ -7,6 +7,10 @@ import "../token/ERC721/ERC721.sol";
  * This mock just provides a public mint and burn functions for testing purposes
  */
 contract ERC721Mock is ERC721 {
+    constructor() public {
+        ERC721.initialize();
+    }
+
     function mint(address to, uint256 tokenId) public {
         _mint(to, tokenId);
     }

contracts/mocks/ERC721PausableMock.sol

@@ -8,6 +8,11 @@ import "./PauserRoleMock.sol";
  * This mock just provides a public mint, burn and exists functions for testing purposes
  */
 contract ERC721PausableMock is ERC721Pausable, PauserRoleMock {
+    constructor() public {
+        ERC721.initialize();
+        ERC721Pausable.initialize(_msgSender());
+    }
+
     function mint(address to, uint256 tokenId) public {
         super._mint(to, tokenId);
     }

contracts/mocks/EscrowMock.sol

@@ -0,0 +1,9 @@
+pragma solidity ^0.5.0;
+
+import "../payment/escrow/Escrow.sol";
+
+contract EscrowMock is Escrow {
+    constructor() public {
+        Escrow.initialize(_msgSender());
+    }
+}

contracts/mocks/FinalizableCrowdsaleImpl.sol

@@ -6,9 +6,8 @@ import "../crowdsale/distribution/FinalizableCrowdsale.sol";
 contract FinalizableCrowdsaleImpl is FinalizableCrowdsale {
     constructor (uint256 openingTime, uint256 closingTime, uint256 rate, address payable wallet, IERC20 token)
         public
-        Crowdsale(rate, wallet, token)
-        TimedCrowdsale(openingTime, closingTime)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(rate, wallet, token);
+        TimedCrowdsale.initialize(openingTime, closingTime);
     }
 }

contracts/mocks/ForceEther.sol

@@ -0,0 +1,18 @@
+pragma solidity ^0.5.0;
+
+
+// @title Force Ether into a contract.
+// @notice  even
+// if the contract is not payable.
+// @notice To use, construct the contract with the target as argument.
+// @author Remco Bloemen <remco@neufund.org>
+contract ForceEther {
+
+    constructor() public payable {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    function destroyAndSend(address payable recipient) public {
+        selfdestruct(recipient);
+    }
+}

contracts/mocks/GSNBouncerERC20FeeMock.sol

@@ -0,0 +1,22 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "../GSN/GSNRecipient.sol";
+import "../GSN/bouncers/GSNBouncerERC20Fee.sol";
+
+contract GSNBouncerERC20FeeMock is GSNRecipient, GSNBouncerERC20Fee {
+    constructor(string memory name, string memory symbol, uint8 decimals) public {
+        GSNRecipient.initialize();
+        GSNBouncerERC20Fee.initialize(name, symbol, decimals);
+    }
+
+    function mint(address account, uint256 amount) public {
+        _mint(account, amount);
+    }
+
+    event MockFunctionCalled(uint256 senderBalance);
+
+    function mockFunction() public {
+        emit MockFunctionCalled(token().balanceOf(_msgSender()));
+    }
+}

contracts/mocks/GSNBouncerSignatureMock.sol

@@ -0,0 +1,18 @@
+pragma solidity ^0.5.0;
+
+import "@openzeppelin/upgrades/contracts/Initializable.sol";
+import "../GSN/GSNRecipient.sol";
+import "../GSN/bouncers/GSNBouncerSignature.sol";
+
+contract GSNBouncerSignatureMock is GSNRecipient, GSNBouncerSignature {
+    constructor(address trustedSigner) public {
+        GSNRecipient.initialize();
+        GSNBouncerSignature.initialize(trustedSigner);
+    }
+
+    event MockFunctionCalled();
+
+    function mockFunction() public {
+        emit MockFunctionCalled();
+    }
+}

contracts/mocks/GSNContextMock.sol

@@ -0,0 +1,50 @@
+pragma solidity ^0.5.0;
+
+import "./ContextMock.sol";
+import "../GSN/GSNContext.sol";
+import "../GSN/IRelayRecipient.sol";
+
+// By inheriting from GSNContext, Context's internal functions are overridden automatically
+contract GSNContextMock is ContextMock, GSNContext, IRelayRecipient {
+    constructor() public {
+        GSNContext.initialize();
+    }
+
+    function getHubAddr() public view returns (address) {
+        return _getRelayHub();
+    }
+
+    function acceptRelayedCall(
+        address,
+        address,
+        bytes calldata,
+        uint256,
+        uint256,
+        uint256,
+        uint256,
+        bytes calldata,
+        uint256
+    )
+        external
+        view
+        returns (uint256, bytes memory)
+    {
+        return (0, "");
+    }
+
+    function preRelayedCall(bytes calldata) external returns (bytes32) {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    function postRelayedCall(bytes calldata, bool, uint256, bytes32) external {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    function getRelayHub() public view returns (address) {
+        return _getRelayHub();
+    }
+
+    function upgradeRelayHub(address newRelayHub) public {
+        return _upgradeRelayHub(newRelayHub);
+    }
+}

contracts/mocks/GSNRecipientMock.sol

@@ -0,0 +1,29 @@
+pragma solidity ^0.5.0;
+
+import "../GSN/GSNRecipient.sol";
+
+contract GSNRecipientMock is GSNRecipient {
+    constructor() public {
+        GSNRecipient.initialize();
+    }
+
+    function withdrawDeposits(uint256 amount, address payable payee) public {
+        _withdrawDeposits(amount, payee);
+    }
+
+    function acceptRelayedCall(address, address, bytes calldata, uint256, uint256, uint256, uint256, bytes calldata, uint256)
+        external
+        view
+        returns (uint256, bytes memory)
+    {
+        return (0, "");
+    }
+
+    function preRelayedCall(bytes calldata) external returns (bytes32) {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    function postRelayedCall(bytes calldata, bool, uint256, bytes32) external {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+}

contracts/mocks/IncreasingPriceCrowdsaleImpl.sol

@@ -13,10 +13,9 @@ contract IncreasingPriceCrowdsaleImpl is IncreasingPriceCrowdsale {
         uint256 finalRate
     )
         public
-        Crowdsale(initialRate, wallet, token)
-        TimedCrowdsale(openingTime, closingTime)
-        IncreasingPriceCrowdsale(initialRate, finalRate)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(initialRate, wallet, token);
+        TimedCrowdsale.initialize(openingTime, closingTime);
+        IncreasingPriceCrowdsale.initialize(initialRate, finalRate);
     }
 }

contracts/mocks/IndividuallyCappedCrowdsaleImpl.sol

@@ -5,7 +5,8 @@ import "../crowdsale/validation/IndividuallyCappedCrowdsale.sol";
 import "./CapperRoleMock.sol";
 
 contract IndividuallyCappedCrowdsaleImpl is IndividuallyCappedCrowdsale, CapperRoleMock {
-    constructor (uint256 rate, address payable wallet, IERC20 token) public Crowdsale(rate, wallet, token) {
-        // solhint-disable-previous-line no-empty-blocks
+    constructor (uint256 rate, address payable wallet, IERC20 token) public {
+        Crowdsale.initialize(rate, wallet, token);
+        IndividuallyCappedCrowdsale.initialize(_msgSender());
     }
 }

contracts/mocks/MessageHelper.sol

@@ -0,0 +1,51 @@
+pragma solidity ^0.5.0;
+
+
+contract MessageHelper {
+
+    event Show(bytes32 b32, uint256 number, string text);
+    event Buy(bytes32 b32, uint256 number, string text, uint256 value);
+
+    function showMessage(
+        bytes32 _message,
+        uint256 _number,
+        string memory _text
+    )
+        public
+        returns (bool)
+    {
+        emit Show(_message, _number, _text);
+        return true;
+    }
+
+    function buyMessage(
+        bytes32 _message,
+        uint256 _number,
+        string memory _text
+    )
+        public
+        payable
+        returns (bool)
+    {
+        emit Buy(
+            _message,
+            _number,
+            _text,
+            msg.value);
+        return true;
+    }
+
+    function fail() public {
+        require(false);
+    }
+
+    function call(address _to, bytes memory _data) public returns (bool) {
+        // solhint-disable-next-line security/avoid-low-level-calls
+        (bool success,) = _to.call(_data);
+        if (success)
+            return true;
+        else
+            return false;
+    }
+
+}

contracts/mocks/MintedCrowdsaleImpl.sol

@@ -4,7 +4,7 @@ import "../token/ERC20/ERC20Mintable.sol";
 import "../crowdsale/emission/MintedCrowdsale.sol";
 
 contract MintedCrowdsaleImpl is MintedCrowdsale {
-    constructor (uint256 rate, address payable wallet, ERC20Mintable token) public Crowdsale(rate, wallet, token) {
-        // solhint-disable-previous-line no-empty-blocks
+    constructor (uint256 rate, address payable wallet, ERC20Mintable token) public {
+        Crowdsale.initialize(rate, wallet, token);
     }
 }

contracts/mocks/MinterRoleMock.sol

@@ -3,6 +3,10 @@ pragma solidity ^0.5.2;
 import "../access/roles/MinterRole.sol";
 
 contract MinterRoleMock is MinterRole {
+    constructor() public {
+        MinterRole.initialize(_msgSender());
+    }
+
     function removeMinter(address account) public {
         _removeMinter(account);
     }

contracts/mocks/OwnableMock.sol

@@ -3,5 +3,7 @@ pragma solidity ^0.5.2;
 import "../ownership/Ownable.sol";
 
 contract OwnableMock is Ownable {
-    // solhint-disable-previous-line no-empty-blocks
+    constructor() public {
+        Ownable.initialize(_msgSender());
+    }
 }

contracts/mocks/PausableCrowdsaleImpl.sol

@@ -4,7 +4,8 @@ import "../token/ERC20/ERC20.sol";
 import "../crowdsale/validation/PausableCrowdsale.sol";
 
 contract PausableCrowdsaleImpl is PausableCrowdsale {
-    constructor (uint256 _rate, address payable _wallet, ERC20 _token) public Crowdsale(_rate, _wallet, _token) {
-        // solhint-disable-previous-line no-empty-blocks
+    constructor (uint256 _rate, address payable _wallet, ERC20 _token) public {
+        Crowdsale.initialize(_rate, _wallet, _token);
+        PausableCrowdsale.initialize(_msgSender());
     }
 }

contracts/mocks/PausableMock.sol

@@ -9,6 +9,8 @@ contract PausableMock is Pausable, PauserRoleMock {
     uint256 public count;
 
     constructor () public {
+        Pausable.initialize(_msgSender());
+
         drasticMeasureTaken = false;
         count = 0;
     }

contracts/mocks/PauserRoleMock.sol

@@ -3,6 +3,10 @@ pragma solidity ^0.5.2;
 import "../access/roles/PauserRole.sol";
 
 contract PauserRoleMock is PauserRole {
+    constructor () public {
+        PauserRole.initialize(_msgSender());
+    }
+
     function removePauser(address account) public {
         _removePauser(account);
     }

contracts/mocks/PaymentSplitterMock.sol

@@ -0,0 +1,9 @@
+pragma solidity ^0.5.0;
+
+import "../payment/PaymentSplitter.sol";
+
+contract PaymentSplitterMock is PaymentSplitter {
+    constructor(address[] memory payees, uint256[] memory shares) public {
+        PaymentSplitter.initialize(payees, shares);
+    }
+}

contracts/mocks/PostDeliveryCrowdsaleImpl.sol

@@ -6,9 +6,8 @@ import "../crowdsale/distribution/PostDeliveryCrowdsale.sol";
 contract PostDeliveryCrowdsaleImpl is PostDeliveryCrowdsale {
     constructor (uint256 openingTime, uint256 closingTime, uint256 rate, address payable wallet, IERC20 token)
         public
-        TimedCrowdsale(openingTime, closingTime)
-        Crowdsale(rate, wallet, token)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(rate, wallet, token);
+        TimedCrowdsale.initialize(openingTime, closingTime);
     }
 }

contracts/mocks/PullPaymentMock.sol

@@ -5,7 +5,7 @@ import "../payment/PullPayment.sol";
 // mock class using PullPayment
 contract PullPaymentMock is PullPayment {
     constructor () public payable {
-        // solhint-disable-previous-line no-empty-blocks
+        PullPayment.initialize();
     }
 
     // test helper function to call asyncTransfer

contracts/mocks/ReentrancyAttack.sol

@@ -1,9 +1,10 @@
 pragma solidity ^0.5.2;
 
-contract ReentrancyAttack {
+import "../GSN/Context.sol";
+contract ReentrancyAttack is Context {
     function callSender(bytes4 data) public {
         // solhint-disable-next-line avoid-low-level-calls
-        (bool success,) = msg.sender.call(abi.encodeWithSelector(data));
-        require(success);
+        (bool success,) = _msgSender().call(abi.encodeWithSelector(data));
+        require(success, "ReentrancyAttack: failed call");
     }
 }

contracts/mocks/ReentrancyMock.sol

@@ -7,6 +7,7 @@ contract ReentrancyMock is ReentrancyGuard {
     uint256 public counter;
 
     constructor () public {
+        ReentrancyGuard.initialize();
         counter = 0;
     }
 

contracts/mocks/RefundEscrowMock.sol

@@ -0,0 +1,9 @@
+pragma solidity ^0.5.0;
+
+import "../payment/escrow/RefundEscrow.sol";
+
+contract RefundEscrowMock is RefundEscrow {
+    constructor(address payable beneficiary) public {
+        RefundEscrow.initialize(beneficiary, _msgSender());
+    }
+}

contracts/mocks/RefundableCrowdsaleImpl.sol

@@ -3,7 +3,7 @@ pragma solidity ^0.5.2;
 import "../token/ERC20/IERC20.sol";
 import "../crowdsale/distribution/RefundableCrowdsale.sol";
 
-contract RefundableCrowdsaleImpl is RefundableCrowdsale {
+contract RefundableCrowdsaleImpl is Crowdsale, TimedCrowdsale, RefundableCrowdsale {
     constructor (
         uint256 openingTime,
         uint256 closingTime,
@@ -13,10 +13,9 @@ contract RefundableCrowdsaleImpl is RefundableCrowdsale {
         uint256 goal
     )
         public
-        Crowdsale(rate, wallet, token)
-        TimedCrowdsale(openingTime, closingTime)
-        RefundableCrowdsale(goal)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(rate, wallet, token);
+        TimedCrowdsale.initialize(openingTime, closingTime);
+        RefundableCrowdsale.initialize(goal);
     }
 }

contracts/mocks/RefundablePostDeliveryCrowdsaleImpl.sol

@@ -13,10 +13,9 @@ contract RefundablePostDeliveryCrowdsaleImpl is RefundablePostDeliveryCrowdsale
         uint256 goal
     )
         public
-        Crowdsale(rate, wallet, token)
-        TimedCrowdsale(openingTime, closingTime)
-        RefundableCrowdsale(goal)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(rate, wallet, token);
+        TimedCrowdsale.initialize(openingTime, closingTime);
+        RefundableCrowdsale.initialize(goal);
     }
 }

contracts/mocks/SafeERC20Helper.sol

@@ -1,9 +1,10 @@
 pragma solidity ^0.5.2;
 
+import "../GSN/Context.sol";
 import "../token/ERC20/IERC20.sol";
 import "../token/ERC20/SafeERC20.sol";
 
-contract ERC20ReturnFalseMock {
+contract ERC20ReturnFalseMock is Context {
     uint256 private _allowance;
 
     // IERC20's functions are not pure, but these mock implementations are: to prevent Solidity from issuing warnings,
@@ -31,7 +32,7 @@ contract ERC20ReturnFalseMock {
     }
 }
 
-contract ERC20ReturnTrueMock {
+contract ERC20ReturnTrueMock is Context {
     mapping (address => uint256) private _allowances;
 
     // IERC20's functions are not pure, but these mock implementations are: to prevent Solidity from issuing warnings,
@@ -54,7 +55,7 @@ contract ERC20ReturnTrueMock {
     }
 
     function setAllowance(uint256 allowance_) public {
-        _allowances[msg.sender] = allowance_;
+        _allowances[_msgSender()] = allowance_;
     }
 
     function allowance(address owner, address) public view returns (uint256) {
@@ -62,7 +63,7 @@ contract ERC20ReturnTrueMock {
     }
 }
 
-contract ERC20NoReturnMock {
+contract ERC20NoReturnMock is Context {
     mapping (address => uint256) private _allowances;
 
     // IERC20's functions are not pure, but these mock implementations are: to prevent Solidity from issuing warnings,
@@ -82,7 +83,7 @@ contract ERC20NoReturnMock {
     }
 
     function setAllowance(uint256 allowance_) public {
-        _allowances[msg.sender] = allowance_;
+        _allowances[_msgSender()] = allowance_;
     }
 
     function allowance(address owner, address) public view returns (uint256) {
@@ -90,7 +91,7 @@ contract ERC20NoReturnMock {
     }
 }
 
-contract SafeERC20Wrapper {
+contract SafeERC20Wrapper is Context {
     using SafeERC20 for IERC20;
 
     IERC20 private _token;

contracts/mocks/SampleCrowdsaleMock.sol

@@ -0,0 +1,26 @@
+pragma solidity ^0.5.0;
+
+import "../examples/SampleCrowdsale.sol";
+
+
+contract SampleCrowdsaleTokenMock is SampleCrowdsaleToken {
+    constructor() public {
+        SampleCrowdsaleToken.initialize(_msgSender());
+    }
+}
+
+contract SampleCrowdsaleMock is SampleCrowdsale {
+    constructor(
+        uint256 openingTime,
+        uint256 closingTime,
+        uint256 rate,
+        address payable wallet,
+        uint256 cap,
+        ERC20Mintable token,
+        uint256 goal
+    )
+        public
+    {
+        SampleCrowdsale.initialize(openingTime, closingTime, rate, wallet, cap, token, goal);
+    }
+}

contracts/mocks/SecondaryMock.sol

@@ -3,6 +3,10 @@ pragma solidity ^0.5.2;
 import "../ownership/Secondary.sol";
 
 contract SecondaryMock is Secondary {
+    constructor() public {
+        Secondary.initialize(_msgSender());
+    }
+
     function onlyPrimaryMock() public view onlyPrimary {
         // solhint-disable-previous-line no-empty-blocks
     }

contracts/mocks/SignatureBouncerMock.sol

@@ -4,6 +4,10 @@ import "../drafts/SignatureBouncer.sol";
 import "./SignerRoleMock.sol";
 
 contract SignatureBouncerMock is SignatureBouncer, SignerRoleMock {
+    constructor() public {
+        SignatureBouncer.initialize(_msgSender());
+    }
+
     function checkValidSignature(address account, bytes memory signature)
         public view returns (bool)
     {

contracts/mocks/SignerRoleMock.sol

@@ -3,6 +3,10 @@ pragma solidity ^0.5.2;
 import "../access/roles/SignerRole.sol";
 
 contract SignerRoleMock is SignerRole {
+    constructor() public {
+        SignerRole.initialize(_msgSender());
+    }
+
     function removeSigner(address account) public {
         _removeSigner(account);
     }

contracts/mocks/SimpleTokenMock.sol

@@ -0,0 +1,9 @@
+pragma solidity ^0.5.0;
+
+import "../examples/SimpleToken.sol";
+
+contract SimpleTokenMock is SimpleToken {
+    constructor() public {
+        SimpleToken.initialize(_msgSender());
+    }
+}

contracts/mocks/TimedCrowdsaleImpl.sol

@@ -6,10 +6,9 @@ import "../crowdsale/validation/TimedCrowdsale.sol";
 contract TimedCrowdsaleImpl is TimedCrowdsale {
     constructor (uint256 openingTime, uint256 closingTime, uint256 rate, address payable wallet, IERC20 token)
         public
-        Crowdsale(rate, wallet, token)
-        TimedCrowdsale(openingTime, closingTime)
     {
-        // solhint-disable-previous-line no-empty-blocks
+        Crowdsale.initialize(rate, wallet, token);
+        TimedCrowdsale.initialize(openingTime, closingTime);
     }
 
     function extendTime(uint256 closingTime) public {

contracts/mocks/TokenTimelockMock.sol

@@ -0,0 +1,13 @@
+pragma solidity ^0.5.0;
+
+import "../token/ERC20/TokenTimelock.sol";
+
+contract TokenTimelockMock is TokenTimelock {
+    constructor(
+        IERC20 token,
+        address beneficiary,
+        uint256 releaseTime
+    ) public {
+        TokenTimelock.initialize(token, beneficiary, releaseTime);
+    }
+}

contracts/mocks/TokenVestingMock.sol

@@ -0,0 +1,22 @@
+pragma solidity ^0.5.0;
+
+import "../drafts/TokenVesting.sol";
+
+contract TokenVestingMock is TokenVesting {
+    constructor(
+        address beneficiary,
+        uint256 start,
+        uint256 cliffDuration,
+        uint256 duration,
+        bool revocable
+    ) public {
+        TokenVesting.initialize(
+            beneficiary,
+            start,
+            cliffDuration,
+            duration,
+            revocable,
+            _msgSender()
+        );
+    }
+}

contracts/mocks/WhitelistAdminRoleMock.sol

@@ -3,6 +3,10 @@ pragma solidity ^0.5.2;
 import "../access/roles/WhitelistAdminRole.sol";
 
 contract WhitelistAdminRoleMock is WhitelistAdminRole {
+    constructor () public {
+        WhitelistAdminRole.initialize(_msgSender());
+    }
+
     function removeWhitelistAdmin(address account) public {
         _removeWhitelistAdmin(account);
     }