add ERC20 preapproved conduit

src/lib/Constants.sol

@@ -12,7 +12,13 @@ uint256 constant SOLADY_ERC1155_MASTER_SLOT_SEED = 0x9a31110384e0b0c9;
 /// @dev `keccak256(bytes("TransferSingle(address,address,address,uint256,uint256)"))`.
 uint256 constant SOLADY_TRANSFER_SINGLE_EVENT_SIGNATURE =
     0xc3d58168c5ae7397731d063d5bbf3d657854427343f4c083240f7aacaa2d0f62;
-
 /// @dev `keccak256(bytes("TransferBatch(address,address,address,uint256[],uint256[])"))`.
 uint256 constant SOLADY_TRANSFER_BATCH_EVENT_SIGNATURE =
     0x4a39dc06d4c0dbc64b70af90fd698a233a518aa5d07e595d983b8c0526c8f7fb;
+/// @dev Solady ERC20 allowance slot seed.
+uint256 constant SOLADY_ERC20_ALLOWANCE_SLOT_SEED = 0x7f5e9f20;
+/// @dev Solady ERC20 balance slot seed.
+uint256 constant SOLADY_ERC20_BALANCE_SLOT_SEED = 0x87a211a2;
+/// @dev `keccak256(bytes("Transfer(address,address,uint256)"))`.
+uint256 constant SOLADY_ERC20_TRANSFER_EVENT_SIGNATURE =
+    0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef;

src/reference/tokens/erc20/ERC20Preapproved_OZ.sol

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+import {ERC20ConduitPreapproved_OZ, ERC20} from "../../../tokens/erc20/ERC20ConduitPreapproved_OZ.sol";
+
+contract ERC20_OZ is ERC20ConduitPreapproved_OZ {
+    constructor() ERC20("ERC20_OZ", "ERC20_OZ") {}
+
+    function mint(address to, uint256 amount) public {
+        _mint(to, amount);
+    }
+}

src/reference/tokens/erc20/ERC20Preapproved_Solady.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+import {ERC20ConduitPreapproved_Solady, ERC20} from "../../../tokens/erc20/ERC20ConduitPreapproved_Solady.sol";
+
+contract ERC20_Solady is ERC20ConduitPreapproved_Solady {
+    function mint(address to, uint256 amount) public {
+        _mint(to, amount);
+    }
+
+    function name() public pure override returns (string memory) {
+        return "Test";
+    }
+
+    function symbol() public pure override returns (string memory) {
+        return "TST";
+    }
+}

src/tokens/erc20/ERC20ConduitPreapproved_OZ.sol

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+import {ERC20} from "openzeppelin-contracts/token/ERC20/ERC20.sol";
+import {CONDUIT} from "../../lib/Constants.sol";
+import {IPreapprovalForAll} from "../../interfaces/IPreapprovalForAll.sol";
+
+abstract contract ERC20ConduitPreapproved_OZ is ERC20, IPreapprovalForAll {
+    constructor() {
+        emit PreapprovalForAll(CONDUIT, true);
+    }
+
+    /**
+     * @param owner Owner of tokens
+     * @param spender Account to check allowance of `owner`'s tokens
+     * @dev If `spender` is `CONDUIT` and allowance is 0, return `type(uint256).max`, since users must explicitly revoke the pre-approved conduit.
+     *      Setting an allowance of 0 for the conduit with `approve` will revoke the pre-approval.
+     */
+    function allowance(address owner, address spender) public view virtual override returns (uint256) {
+        uint256 allowance = super.allowance(owner, spender);
+        if (spender == CONDUIT) {
+            if (allowance == 0) {
+                return type(uint256).max;
+            } else if (allowance == type(uint256).max) {
+                return 0;
+            }
+        }
+        return allowance;
+    }
+
+    /**
+     * @param owner Owner of tokens
+     * @param spender Account to approve allowance of `owner`'s tokens
+     * @param value Amount to approve
+     * @param emitEvent Whether to emit the Approval event
+     * @dev `allowance` inverts the value of the approval if `spender` is `CONDUIT`, since users must explicitly revoke the pre-approved conduit.
+     *       E.g. if 0 is passed, it is stored as `type(uint256).max`, and if `type(uint256).max` is passed, it is stored as 0.
+     */
+    function _approve(address owner, address spender, uint256 value, bool emitEvent) internal virtual override {
+        if (spender == CONDUIT) {
+            if (value == 0) {
+                value = type(uint256).max;
+            } else if (value == type(uint256).max) {
+                value = 0;
+            }
+        }
+        super._approve(owner, spender, value, emitEvent);
+    }
+}

src/tokens/erc20/ERC20ConduitPreapproved_Solady.sol

@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+import {ERC20} from "solady/src/tokens/ERC20.sol";
+import {
+    CONDUIT,
+    SOLADY_ERC20_ALLOWANCE_SLOT_SEED,
+    SOLADY_ERC20_BALANCE_SLOT_SEED,
+    SOLADY_ERC20_TRANSFER_EVENT_SIGNATURE
+} from "../../lib/Constants.sol";
+import {IPreapprovalForAll} from "../../interfaces/IPreapprovalForAll.sol";
+
+abstract contract ERC20ConduitPreapproved_Solady is ERC20, IPreapprovalForAll {
+    constructor() {
+        emit PreapprovalForAll(CONDUIT, true);
+    }
+
+    /**
+     * @param owner Owner of tokens
+     * @param spender Account to check allowance of `owner`'s tokens
+     * @dev If `spender` is `CONDUIT` and allowance is 0, return `type(uint256).max`, since users must explicitly revoke the pre-approved conduit.
+     *      Setting an allowance of 0 for the conduit with `approve` will revoke the pre-approval.
+     */
+    function allowance(address owner, address spender) public view virtual override returns (uint256) {
+        uint256 allowance_ = super.allowance(owner, spender);
+        if (spender == CONDUIT) {
+            if (allowance_ == 0) {
+                return type(uint256).max;
+            } else if (allowance_ == type(uint256).max) {
+                return 0;
+            }
+        }
+        return allowance_;
+    }
+
+    /**
+     * @param spender Account to approve allowance of `msg.sender`'s tokens
+     * @param amount Amount to approve
+     * @dev `allowance` inverts the value of the approval if `spender` is `CONDUIT`, since users must explicitly revoke the pre-approved conduit.
+     *       E.g. if 0 is passed, it is stored as `type(uint256).max`, and if `type(uint256).max` is passed, it is stored as 0.
+     */
+    function approve(address spender, uint256 amount) public virtual override returns (bool) {
+        if (spender == CONDUIT) {
+            if (amount == 0) {
+                amount = type(uint256).max;
+            } else if (amount == type(uint256).max) {
+                amount = 0;
+            }
+        }
+        super._approve(msg.sender, spender, amount);
+        return true;
+    }
+
+    function transferFrom(address from, address to, uint256 amount) public virtual override returns (bool) {
+        _beforeTokenTransfer(from, to, amount);
+        /// @solidity memory-safe-assembly
+        assembly {
+            let from_ := shl(96, from)
+            // Compute the allowance slot and load its value.
+            mstore(0x20, caller())
+            mstore(0x0c, or(from_, SOLADY_ERC20_ALLOWANCE_SLOT_SEED))
+            let allowanceSlot := keccak256(0x0c, 0x34)
+            let allowance_ := sload(allowanceSlot)
+            // If the caller is the conduit and allowance is 0, set to type(uint256).max. If the allowance is type(uint256).max, set to 0.
+            let isConduit := eq(caller(), CONDUIT)
+            if isConduit {
+                let conduitAllowance_ := allowance_
+                if eq(allowance_, 0) { conduitAllowance_ := not(0) }
+                if eq(allowance_, not(0)) { conduitAllowance_ := 0 }
+                if iszero(eq(allowance_, conduitAllowance_)) { allowance_ := conduitAllowance_ }
+            }
+            // If the allowance is not the maximum uint256 value.
+            if add(allowance_, 1) {
+                // Revert if the amount to be transferred exceeds the allowance.
+                if gt(amount, allowance_) {
+                    mstore(0x00, 0x13be252b) // `InsufficientAllowance()`.
+                    revert(0x1c, 0x04)
+                }
+                // Subtract and store the updated allowance.
+                sstore(allowanceSlot, sub(allowance_, amount))
+            }
+            // Compute the balance slot and load its value.
+            mstore(0x0c, or(from_, SOLADY_ERC20_BALANCE_SLOT_SEED))
+            let fromBalanceSlot := keccak256(0x0c, 0x20)
+            let fromBalance := sload(fromBalanceSlot)
+            // Revert if insufficient balance.
+            if gt(amount, fromBalance) {
+                mstore(0x00, 0xf4d678b8) // `InsufficientBalance()`.
+                revert(0x1c, 0x04)
+            }
+            // Subtract and store the updated balance.
+            sstore(fromBalanceSlot, sub(fromBalance, amount))
+            // Compute the balance slot of `to`.
+            mstore(0x00, to)
+            let toBalanceSlot := keccak256(0x0c, 0x20)
+            // Add and store the updated balance of `to`.
+            // Will not overflow because the sum of all user balances
+            // cannot exceed the maximum uint256 value.
+            sstore(toBalanceSlot, add(sload(toBalanceSlot), amount))
+            // Emit the {Transfer} event.
+            mstore(0x20, amount)
+            log3(0x20, 0x20, SOLADY_ERC20_TRANSFER_EVENT_SIGNATURE, shr(96, from_), shr(96, mload(0x0c)))
+        }
+        _afterTokenTransfer(from, to, amount);
+        return true;
+    }
+
+    function _spendAllowance(address owner, address spender, uint256 amount) internal virtual override {
+        if (spender == CONDUIT) {
+            uint256 allowance_ = super.allowance(owner, spender);
+            if (allowance_ == type(uint256).max) {
+                // Max allowance, no need to spend.
+                return;
+            } else if (allowance_ == 0) {
+                revert InsufficientAllowance();
+            }
+        }
+        super._spendAllowance(owner, spender, amount);
+    }
+}

test/reference/ExampleNFT.t.sol

@@ -8,7 +8,7 @@ contract ExampleNFTTest is Test {
     ExampleNFT testExampleNft;
 
     function setUp() public {
-        testExampleNft = new ExampleNFT('Example', 'EXNFT');
+        testExampleNft = new ExampleNFT("Example", "EXNFT");
     }
 
     function testName() public {

test/tokens/ERC20ConduitPreapproved_OZ.t.sol

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+import {Test} from "forge-std/Test.sol";
+import {ERC20_OZ} from "src/reference/tokens/erc20/ERC20Preapproved_OZ.sol";
+import {CONDUIT} from "src/lib/Constants.sol";
+import {IPreapprovalForAll} from "src/interfaces/IPreapprovalForAll.sol";
+
+contract ERC20ConduitPreapproved_OZTest is Test, IPreapprovalForAll {
+    ERC20_OZ test;
+
+    function setUp() public {
+        test = new ERC20_OZ();
+    }
+
+    function testConstructorEvent() public {
+        vm.expectEmit(true, true, false, false);
+        emit PreapprovalForAll(CONDUIT, true);
+        new ERC20_OZ();
+    }
+
+    function testConduitPreapproved(address acct) public {
+        if (acct == address(0)) {
+            acct = address(1);
+        }
+        assertEq(test.allowance(acct, CONDUIT), type(uint256).max);
+        vm.prank(acct);
+        test.approve(CONDUIT, 0);
+        assertEq(test.allowance(acct, CONDUIT), 0);
+        vm.prank(acct);
+        test.approve(CONDUIT, 1 ether);
+        assertEq(test.allowance(acct, CONDUIT), 1 ether);
+    }
+
+    function testNormalApprovals(address acct, address operator) public {
+        if (acct == address(0)) {
+            acct = address(1);
+        }
+        if (operator == address(0)) {
+            operator = address(1);
+        }
+        vm.assume(operator != CONDUIT);
+        vm.assume(acct != operator);
+        assertEq(test.allowance(acct, operator), 0);
+        vm.prank(acct);
+        test.approve(operator, 1 ether);
+        assertEq(test.allowance(acct, operator), 1 ether);
+        vm.prank(acct);
+        test.approve(operator, 0);
+        assertEq(test.allowance(acct, operator), 0);
+    }
+
+    function testConduitCanTransfer(address acct) public {
+        if (acct == address(0)) {
+            acct = address(1);
+        }
+        test.mint(address(acct), 1);
+        vm.prank(CONDUIT);
+        test.transferFrom(address(acct), address(this), 1);
+    }
+}

test/tokens/ERC20ConduitPreapproved_Solady.t.sol

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+import {Test} from "forge-std/Test.sol";
+import {ERC20_Solady} from "src/reference/tokens/erc20/ERC20Preapproved_Solady.sol";
+import {CONDUIT} from "src/lib/Constants.sol";
+import {IPreapprovalForAll} from "src/interfaces/IPreapprovalForAll.sol";
+
+contract ERC20ConduitPreapproved_SoladyTest is Test, IPreapprovalForAll {
+    ERC20_Solady test;
+
+    function setUp() public {
+        test = new ERC20_Solady();
+    }
+
+    function testConstructorEvent() public {
+        vm.expectEmit(true, true, false, false);
+        emit PreapprovalForAll(CONDUIT, true);
+        new ERC20_Solady();
+    }
+
+    function testConduitPreapproved(address acct) public {
+        if (acct == address(0)) {
+            acct = address(1);
+        }
+        assertEq(test.allowance(acct, CONDUIT), type(uint256).max);
+        vm.prank(acct);
+        test.approve(CONDUIT, 0);
+        assertEq(test.allowance(acct, CONDUIT), 0);
+        vm.prank(acct);
+        test.approve(CONDUIT, 1 ether);
+        assertEq(test.allowance(acct, CONDUIT), 1 ether);
+    }
+
+    function testNormalApprovals(address acct, address operator) public {
+        if (acct == address(0)) {
+            acct = address(1);
+        }
+        if (operator == address(0)) {
+            operator = address(1);
+        }
+        vm.assume(operator != CONDUIT);
+        vm.assume(acct != operator);
+        assertEq(test.allowance(acct, operator), 0);
+        vm.prank(acct);
+        test.approve(operator, 1 ether);
+        assertEq(test.allowance(acct, operator), 1 ether);
+        vm.prank(acct);
+        test.approve(operator, 0);
+        assertEq(test.allowance(acct, operator), 0);
+    }
+
+    function testConduitCanTransfer(address acct) public {
+        if (acct == address(0)) {
+            acct = address(1);
+        }
+        test.mint(address(acct), 1);
+        vm.prank(CONDUIT);
+        test.transferFrom(address(acct), address(this), 1);
+    }
+}