0. 版本

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

0.1 Ownable2Step.sol

Github: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.8.3/contracts/access/Ownable2Step.sol

Ownable2Step库是Ownable库的拓展版本。其提供的访问权限机制同Ownable完全一致，只是owner的更换机制从由原owner直接指定（一次交互）变成原owner指定 + 新owner确认（两次交互）。Ownable2Step库具有Ownable库所有的功能函数。

1. 目标合约

继承Ownable2Step成为一个可调用合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/src/access/MockOwnable2Step.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

import "openzeppelin-contracts/contracts/access/Ownable2Step.sol";

contract MockOwnable2Step is Ownable2Step {
    uint public i;

    function transferOwnershipInternal(address newOwner) external {
        _transferOwnership(newOwner);
    }

    function setI(uint value) external onlyOwner {
        i = value;
    }
}

全部foundry测试合约：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/test/access/Ownable2Step.t.sol

2. 代码精读

2.1 pendingOwner() && transferOwnership(address newOwner) && _transferOwnership(address newOwner)

• pendingOwner()：返回当前合约处于待确认状态的owner地址；
• transferOwnership(address newOwner)：合约当前owner指定新的owner（步骤一），该操作会覆盖之前设置的_pendingOwner。注: 该函数重写了Ownerable库的transferOwnership函数；
• _transferOwnership(address newOwner)：转移本合约owner身份给一个新的地址。注：该函数重写了Ownerable库的_transferOwnership函数且不具有对访问权限的限制；

	// 处于待确认状态的owner地址
    address private _pendingOwner;

    event OwnershipTransferStarted(address indexed previousOwner, address indexed newOwner);

    function pendingOwner() public view virtual returns (address) {
    	// 返回状态变量_pendingOwner
        return _pendingOwner;
    }
    
    function transferOwnership(address newOwner) public virtual override onlyOwner {
        // 新owner地址处于待确认状态，写入状态变量_pendingOwner
        _pendingOwner = newOwner;
        // 抛出event
        emit OwnershipTransferStarted(owner(), newOwner);
    }
    
    function _transferOwnership(address newOwner) internal virtual override {
        // 清空状态变量_pendingOwner
        delete _pendingOwner;
        // 调用Ownerable.transferOwnership()进行owner身份的转移
        super._transferOwnership(newOwner);
    }

foundry代码验证

contract Ownable2StepTest is Test {
    MockOwnable2Step private _testing;

    function setUp() external {
        _testing = new MockOwnable2Step();
    }

    event OwnershipTransferStarted(address indexed previousOwner, address indexed newOwner);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function test_TransferOwnership() external {
        // test for public function: transferOwnership
        assertEq(address(0), _testing.pendingOwner());
        // case 1: pass
        vm.expectEmit(true, true, false, false, address(_testing));
        emit OwnershipTransferStarted(address(this), address(1024));
        _testing.transferOwnership(address(1024));
        assertEq(address(1024), _testing.pendingOwner());

        // test for internal function: _transferOwnership
        // case 1: pass with clearing pending owner and new owner transferred
        vm.expectEmit(true, true, false, false, address(_testing));
        emit OwnershipTransferred(address(this), address(2048));
        _testing.transferOwnershipInternal(address(2048));
        // new owner transferred
        assertEq(address(2048), _testing.owner());
        // clear the pending owner
        assertEq(address(0), _testing.pendingOwner());
    }
}

2.2 acceptOwnership()

新owner确认owner身份的转移（步骤二）。

    function acceptOwnership() external {
        address sender = _msgSender();
        // 确认本次调用者为处于待确认状态的owner地址，否则revert
        require(pendingOwner() == sender, "Ownable2Step: caller is not the new owner");
        // 将owner身份转移给本次调用者（即处于待确认状态的owner地址）
        _transferOwnership(sender);
    }

foundry代码验证

contract Ownable2StepTest is Test {
    MockOwnable2Step private _testing;

    function setUp() external {
        _testing = new MockOwnable2Step();
    }

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function test_AcceptOwnership() external {
        // case 1: pass
        _testing.transferOwnership(address(1024));
        assertEq(address(1024), _testing.pendingOwner());
        assertEq(address(this), _testing.owner());
        vm.prank(address(1024));
        vm.expectEmit(true, true, false, false, address(_testing));
        emit OwnershipTransferred(address(this), address(1024));
        _testing.acceptOwnership();
        // clear the pending owner
        assertEq(address(0), _testing.pendingOwner());
        // new owner transferred
        assertEq(address(1024), _testing.owner());

        // case 2: revert if _msgSender() is not pending owner
        // current pending owner is address(0)
        vm.expectRevert("Ownable2Step: caller is not the new owner");
        vm.prank(address(1));
        _testing.acceptOwnership();
    }
    
    function test_OnlyOwner() external {
        assertEq(address(this), _testing.owner());

        // test for modifier: onlyOwner
        // case 1: pass the check of modifier
        assertEq(0, _testing.i());
        _testing.setI(1024);
        assertEq(1024, _testing.i());
        // case 2: revert if the msgSender() is not owner
        vm.prank(address(1024));
        vm.expectRevert("Ownable: caller is not the owner");
        _testing.setI(1024);
    }
}

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