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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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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);
}
}

27
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));
}
@ -318,7 +339,9 @@ abstract contract ERC20 is Context, IERC20, IERC20Metadata, IERC20Errors {
revert ERC20InvalidSpender(address(0));
}
_allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
if (emitEvent) {
emit Approval(owner, spender, 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);
}
}
}