Michael.W基于Foundry精读Openzeppelin第40期—

Michael.W基于Foundry精读Openzeppelin第40期——ERC20Burnable.sol

- - 0. 版本
  - - 0.1 ERC20Burnable.sol
  - 1. 目标合约
  - 2. 代码精读
  - - 2.1 burn(uint256 amount)
    - 2.2 burnFrom(address account, uint256 amount)

0. 版本

[openzeppelin]：v4.8.3，[forge-std]：v1.5.6

0.1 ERC20Burnable.sol

Github: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.8.3/contracts/token/ERC20/extensions/ERC20Burnable.sol

ERC20Burnable库是ERC20的拓展。该库允许用户销毁自己和给自己授权的人名下的token。

1. 目标合约

继承ERC20Burnable合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/src/token/ERC20/extensions/MockERC20Burnable.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;import "openzeppelin-contracts/contracts/token/ERC20/extensions/ERC20Burnable.sol";contract MockERC20Burnable is ERC20Burnable {constructor(string memory name, string memory symbol)ERC20(name, symbol) {}function mint(address account, uint amount) external {_mint(account, amount);}
}

全部foundry测试合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/test/token/ERC20/extensions/ERC20Burnable.t.sol

2. 代码精读

2.1 burn(uint256 amount)

调用者销毁自己名下数量为amount的token。

    function burn(uint256 amount) public virtual {// 调用ERC20._burn()进行销毁_burn(_msgSender(), amount);}

foundry代码验证：

contract ERC20BurnableTest is Test {MockERC20Burnable private _testing = new MockERC20Burnable("test name", "test symbol");address private user1 = address(1);function setUp() external {_testing.mint(user1, 100);}function test_Burn() external {vm.prank(user1);_testing.burn(1);assertEq(_testing.balanceOf(user1), 100 - 1);// revert if burn more than balancevm.expectRevert("ERC20: burn amount exceeds balance");_testing.burn(100);}
}

2.2 burnFrom(address account, uint256 amount)

调用者销毁account名下数量为amount的token。要求调用者必须拥有account地址足够的授权额度。

注：销毁过程同样会减少account给调用者的授权额度。如果授权额度为type(uint).max，那么该过程将不做授权额度的检查和更新.

    function burnFrom(address account, uint256 amount) public virtual {// 调用ERC20._spendAllowance()进行授权额度的检查和更新_spendAllowance(account, _msgSender(), amount);// 调用ERC20._burn()进行销毁_burn(account, amount);}

foundry代码验证：

contract ERC20BurnableTest is Test {MockERC20Burnable private _testing = new MockERC20Burnable("test name", "test symbol");address private user1 = address(1);address private user2 = address(2);function setUp() external {_testing.mint(user1, 100);}function test_BurnFrom() external {// revert without approvevm.prank(user2);vm.expectRevert("ERC20: insufficient allowance");_testing.burnFrom(user1, 1);// revert if burn more than allowancevm.prank(user1);_testing.approve(user2, 1);vm.prank(user2);vm.expectRevert("ERC20: insufficient allowance");_testing.burnFrom(user1, 2);// revert if burn more than balancevm.prank(user1);_testing.approve(user2, 100 + 1);vm.prank(user2);vm.expectRevert("ERC20: burn amount exceeds balance");_testing.burnFrom(user1, 100 + 1);// passvm.prank(user2);_testing.burnFrom(user1, 10);assertEq(_testing.allowance(user1, user2), 101 - 10);assertEq(_testing.balanceOf(user1), 100 - 10);// allowance not changed if it was set to type(uint).maxvm.prank(user1);_testing.approve(user2, type(uint).max);vm.prank(user2);_testing.burnFrom(user1, 10);assertEq(_testing.allowance(user1, user2), type(uint).max);}
}