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Do not emit Approval event when calling transferFrom (#4370)

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Co-authored-by: Ernesto García <ernestognw@gmail.com>
Co-authored-by: Francisco <fg@frang.io>
This commit is contained in:
Hadrien Croubois
2023-06-22 18:41:56 +02:00
committed by GitHub
parent 6ddacdbde8
commit 1e0e4e20bb
6 changed files with 357 additions and 307 deletions
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5
.changeset/heavy-drinks-fail.md Normal file
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@ -0,0 +1,5 @@
---
'openzeppelin-solidity': major
---
`ERC20`: Remove `Approval` event previously emitted in `transferFrom` to indicate that part of the allowance was consumed. With this change, allowances are no longer reconstructible from events. See the code for guidelines on how to re-enable this event if needed.

10
contracts/mocks/token/ERC20ApprovalMock.sol Normal file
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@ -0,0 +1,10 @@
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;
import "../../token/ERC20/ERC20.sol";
abstract contract ERC20ApprovalMock is ERC20 {
function _approve(address owner, address spender, uint256 amount, bool) internal virtual override {
super._approve(owner, spender, amount, true);
}
}

25
contracts/token/ERC20/ERC20.sol
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@ -311,6 +311,27 @@ abstract contract ERC20 is Context, IERC20, IERC20Metadata, IERC20Errors {
* - `spender` cannot be the zero address.
*/
function _approve(address owner, address spender, uint256 amount) internal virtual {
_approve(owner, spender, amount, true);
}
/**
* @dev Alternative version of {_approve} with an optional flag that can enable or disable the Approval event.
*
* By default (when calling {_approve}) the flag is set to true. On the other hand, approval changes made by
* `_spendAllowance` during the `transferFrom` operation set the flag to false. This saves gas by not emitting any
* `Approval` event during `transferFrom` operations.
*
* Anyone who wishes to continue emitting `Approval` events on the`transferFrom` operation can force the flag to true
* using the following override:
* ```
* function _approve(address owner, address spender, uint256 amount, bool) internal virtual override {
* super._approve(owner, spender, amount, true);
* }
* ```
*
* Requirements are the same as {_approve}.
*/
function _approve(address owner, address spender, uint256 amount, bool emitEvent) internal virtual {
if (owner == address(0)) {
revert ERC20InvalidApprover(address(0));
}
@ -318,8 +339,10 @@ abstract contract ERC20 is Context, IERC20, IERC20Metadata, IERC20Errors {
revert ERC20InvalidSpender(address(0));
}
_allowances[owner][spender] = amount;
if (emitEvent) {
emit Approval(owner, spender, amount);
}
}
/**
* @dev Updates `owner` s allowance for `spender` based on spent `amount`.
@ -336,7 +359,7 @@ abstract contract ERC20 is Context, IERC20, IERC20Metadata, IERC20Errors {
revert ERC20InsufficientAllowance(spender, currentAllowance, amount);
}
unchecked {
_approve(owner, spender, currentAllowance - amount);
_approve(owner, spender, currentAllowance - amount, false);
}
}
}

14
test/token/ERC20/ERC20.behavior.js
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@ -4,7 +4,10 @@ const { ZERO_ADDRESS, MAX_UINT256 } = constants;
const { expectRevertCustomError } = require('../../helpers/customError');
function shouldBehaveLikeERC20(initialSupply, initialHolder, recipient, anotherAccount) {
function shouldBehaveLikeERC20(initialSupply, accounts, opts = {}) {
const [initialHolder, recipient, anotherAccount] = accounts;
const { forcedApproval } = opts;
describe('total supply', function () {
it('returns the total amount of tokens', async function () {
expect(await this.token.totalSupply()).to.be.bignumber.equal(initialSupply);
@ -70,6 +73,7 @@ function shouldBehaveLikeERC20(initialSupply, initialHolder, recipient, anotherA
});
});
if (forcedApproval) {
it('emits an approval event', async function () {
expectEvent(await this.token.transferFrom(tokenOwner, to, amount, { from: spender }), 'Approval', {
owner: tokenOwner,
@ -77,6 +81,14 @@ function shouldBehaveLikeERC20(initialSupply, initialHolder, recipient, anotherA
value: await this.token.allowance(tokenOwner, spender),
});
});
} else {
it('does not emit an approval event', async function () {
expectEvent.notEmitted(
await this.token.transferFrom(tokenOwner, to, amount, { from: spender }),
'Approval',
);
});
}
});
describe('when the token owner does not have enough balance', function () {

36
test/token/ERC20/ERC20.test.js
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@ -9,22 +9,27 @@ const {
} = require('./ERC20.behavior');
const { expectRevertCustomError } = require('../../helpers/customError');
const ERC20 = artifacts.require('$ERC20');
const ERC20Decimals = artifacts.require('$ERC20DecimalsMock');
const TOKENS = [
{ Token: artifacts.require('$ERC20') },
{ Token: artifacts.require('$ERC20ApprovalMock'), forcedApproval: true },
];
contract('ERC20', function (accounts) {
const [initialHolder, recipient, anotherAccount] = accounts;
const [initialHolder, recipient] = accounts;
const name = 'My Token';
const symbol = 'MTKN';
const initialSupply = new BN(100);
for (const { Token, forcedApproval } of TOKENS) {
describe(`using ${Token._json.contractName}`, function () {
beforeEach(async function () {
this.token = await ERC20.new(name, symbol);
this.token = await Token.new(name, symbol);
await this.token.$_mint(initialHolder, initialSupply);
});
shouldBehaveLikeERC20(initialSupply, accounts, { forcedApproval });
it('has a name', async function () {
expect(await this.token.name()).to.equal(name);
});
@ -37,17 +42,6 @@ contract('ERC20', function (accounts) {
expect(await this.token.decimals()).to.be.bignumber.equal('18');
});
describe('set decimals', function () {
const decimals = new BN(6);
it('can set decimals during construction', async function () {
const token = await ERC20Decimals.new(name, symbol, decimals);
expect(await token.decimals()).to.be.bignumber.equal(decimals);
});
});
shouldBehaveLikeERC20(initialSupply, initialHolder, recipient, anotherAccount);
describe('decrease allowance', function () {
describe('when the spender is not the zero address', function () {
const spender = recipient;
@ -212,7 +206,9 @@ contract('ERC20', function (accounts) {
describe('_mint', function () {
const amount = new BN(50);
it('rejects a null account', async function () {
await expectRevertCustomError(this.token.$_mint(ZERO_ADDRESS, amount), 'ERC20InvalidReceiver', [ZERO_ADDRESS]);
await expectRevertCustomError(this.token.$_mint(ZERO_ADDRESS, amount), 'ERC20InvalidReceiver', [
ZERO_ADDRESS,
]);
});
it('rejects overflow', async function () {
@ -247,7 +243,9 @@ contract('ERC20', function (accounts) {
describe('_burn', function () {
it('rejects a null account', async function () {
await expectRevertCustomError(this.token.$_burn(ZERO_ADDRESS, new BN(1)), 'ERC20InvalidSender', [ZERO_ADDRESS]);
await expectRevertCustomError(this.token.$_burn(ZERO_ADDRESS, new BN(1)), 'ERC20InvalidSender', [
ZERO_ADDRESS,
]);
});
describe('for a non zero account', function () {
@ -363,3 +361,5 @@ contract('ERC20', function (accounts) {
});
});
});
}
});

20
test/token/ERC20/extensions/ERC20Wrapper.test.js
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@ -10,7 +10,7 @@ const ERC20Decimals = artifacts.require('$ERC20DecimalsMock');
const ERC20Wrapper = artifacts.require('$ERC20Wrapper');
contract('ERC20Wrapper', function (accounts) {
const [initialHolder, recipient, anotherAccount] = accounts;
const [initialHolder, receiver] = accounts;
const name = 'My Token';
const symbol = 'MTKN';
@ -85,7 +85,7 @@ contract('ERC20Wrapper', function (accounts) {
it('to other account', async function () {
await this.underlying.approve(this.token.address, initialSupply, { from: initialHolder });
const { tx } = await this.token.depositFor(anotherAccount, initialSupply, { from: initialHolder });
const { tx } = await this.token.depositFor(receiver, initialSupply, { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: initialHolder,
to: this.token.address,
@ -93,7 +93,7 @@ contract('ERC20Wrapper', function (accounts) {
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: ZERO_ADDRESS,
to: anotherAccount,
to: receiver,
value: initialSupply,
});
});
@ -144,10 +144,10 @@ contract('ERC20Wrapper', function (accounts) {
});
it('to other account', async function () {
const { tx } = await this.token.withdrawTo(anotherAccount, initialSupply, { from: initialHolder });
const { tx } = await this.token.withdrawTo(receiver, initialSupply, { from: initialHolder });
await expectEvent.inTransaction(tx, this.underlying, 'Transfer', {
from: this.token.address,
to: anotherAccount,
to: receiver,
value: initialSupply,
});
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
@ -163,10 +163,10 @@ contract('ERC20Wrapper', function (accounts) {
await this.underlying.approve(this.token.address, initialSupply, { from: initialHolder });
await this.token.depositFor(initialHolder, initialSupply, { from: initialHolder });
const { tx } = await this.token.$_recover(anotherAccount);
const { tx } = await this.token.$_recover(receiver);
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: ZERO_ADDRESS,
to: anotherAccount,
to: receiver,
value: '0',
});
});
@ -174,10 +174,10 @@ contract('ERC20Wrapper', function (accounts) {
it('something to recover', async function () {
await this.underlying.transfer(this.token.address, initialSupply, { from: initialHolder });
const { tx } = await this.token.$_recover(anotherAccount);
const { tx } = await this.token.$_recover(receiver);
await expectEvent.inTransaction(tx, this.token, 'Transfer', {
from: ZERO_ADDRESS,
to: anotherAccount,
to: receiver,
value: initialSupply,
});
});
@ -189,6 +189,6 @@ contract('ERC20Wrapper', function (accounts) {
await this.token.depositFor(initialHolder, initialSupply, { from: initialHolder });
});
shouldBehaveLikeERC20(initialSupply, initialHolder, recipient, anotherAccount);
shouldBehaveLikeERC20(initialSupply, accounts);
});
});