Use hardhat-exposed to reduce the need for mocks (#3666)

Co-authored-by: Francisco <fg@frang.io>

contracts/mocks/proxy/BadBeacon.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+contract BadBeaconNoImpl {}
+
+contract BadBeaconNotContract {
+    function implementation() external pure returns (address) {
+        return address(0x1);
+    }
+}

contracts/mocks/proxy/ClashingImplementation.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Implementation contract with an admin() function made to clash with
+ * @dev TransparentUpgradeableProxy's to test correct functioning of the
+ * @dev Transparent Proxy feature.
+ */
+contract ClashingImplementation {
+    function admin() external pure returns (address) {
+        return 0x0000000000000000000000000000000011111142;
+    }
+
+    function delegatedFunction() external pure returns (bool) {
+        return true;
+    }
+}

contracts/mocks/proxy/UUPSLegacy.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "./UUPSUpgradeableMock.sol";
+
+// This contract implements the pre-4.5 UUPS upgrade function with a rollback test.
+// It's used to test that newer UUPS contracts are considered valid upgrades by older UUPS contracts.
+contract UUPSUpgradeableLegacyMock is UUPSUpgradeableMock {
+    // Inlined from ERC1967Upgrade
+    bytes32 private constant _ROLLBACK_SLOT = 0x4910fdfa16fed3260ed0e7147f7cc6da11a60208b5b9406d12a635614ffd9143;
+
+    // ERC1967Upgrade._setImplementation is private so we reproduce it here.
+    // An extra underscore prevents a name clash error.
+    function __setImplementation(address newImplementation) private {
+        require(Address.isContract(newImplementation), "ERC1967: new implementation is not a contract");
+        StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
+    }
+
+    function _upgradeToAndCallSecureLegacyV1(address newImplementation, bytes memory data, bool forceCall) internal {
+        address oldImplementation = _getImplementation();
+
+        // Initial upgrade and setup call
+        __setImplementation(newImplementation);
+        if (data.length > 0 || forceCall) {
+            Address.functionDelegateCall(newImplementation, data);
+        }
+
+        // Perform rollback test if not already in progress
+        StorageSlot.BooleanSlot storage rollbackTesting = StorageSlot.getBooleanSlot(_ROLLBACK_SLOT);
+        if (!rollbackTesting.value) {
+            // Trigger rollback using upgradeTo from the new implementation
+            rollbackTesting.value = true;
+            Address.functionDelegateCall(
+                newImplementation,
+                abi.encodeWithSignature("upgradeTo(address)", oldImplementation)
+            );
+            rollbackTesting.value = false;
+            // Check rollback was effective
+            require(oldImplementation == _getImplementation(), "ERC1967Upgrade: upgrade breaks further upgrades");
+            // Finally reset to the new implementation and log the upgrade
+            _upgradeTo(newImplementation);
+        }
+    }
+
+    // hooking into the old mechanism
+    function upgradeTo(address newImplementation) external override {
+        _upgradeToAndCallSecureLegacyV1(newImplementation, bytes(""), false);
+    }
+
+    function upgradeToAndCall(address newImplementation, bytes memory data) external payable override {
+        _upgradeToAndCallSecureLegacyV1(newImplementation, data, false);
+    }
+}

contracts/mocks/proxy/UUPSUpgradeableMock.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../../proxy/utils/UUPSUpgradeable.sol";
+import "../../utils/Counters.sol";
+
+contract NonUpgradeableMock {
+    Counters.Counter internal _counter;
+
+    function current() external view returns (uint256) {
+        return Counters.current(_counter);
+    }
+
+    function increment() external {
+        return Counters.increment(_counter);
+    }
+}
+
+contract UUPSUpgradeableMock is NonUpgradeableMock, UUPSUpgradeable {
+    // Not having any checks in this function is dangerous! Do not do this outside tests!
+    function _authorizeUpgrade(address) internal override {}
+}
+
+contract UUPSUpgradeableUnsafeMock is UUPSUpgradeableMock {
+    function upgradeTo(address newImplementation) external override {
+        ERC1967Upgrade._upgradeToAndCall(newImplementation, bytes(""), false);
+    }
+
+    function upgradeToAndCall(address newImplementation, bytes memory data) external payable override {
+        ERC1967Upgrade._upgradeToAndCall(newImplementation, data, false);
+    }
+}