Added hardfork support + deterministic state to reference implementation

src/examples/simple/ERC6551Account.sol

@@ -14,7 +14,7 @@ interface IERC6551Account {
         view
         returns (uint256 chainId, address tokenContract, uint256 tokenId);
 
-    function state() external view returns (uint256);
+    function state() external view returns (bytes32);
 
     function isValidSigner(address signer, bytes calldata context)
         external
@@ -30,7 +30,9 @@ interface IERC6551Executable {
 }
 
 contract ERC6551Account is IERC165, IERC1271, IERC6551Account, IERC6551Executable {
-    uint256 public state;
+    uint256 immutable deploymentChainId = block.chainid;
+
+    bytes32 public state;
 
     receive() external payable {}
 
@@ -43,7 +45,7 @@ contract ERC6551Account is IERC165, IERC1271, IERC6551Account, IERC6551Executabl
         require(_isValidSigner(msg.sender), "Invalid signer");
         require(operation == 0, "Only call operations are supported");
 
-        ++state;
+        state = keccak256(abi.encode(state, msg.data));
 
         bool success;
         (success, result) = to.call{value: value}(data);
@@ -96,7 +98,8 @@ contract ERC6551Account is IERC165, IERC1271, IERC6551Account, IERC6551Executabl
 
     function owner() public view virtual returns (address) {
         (uint256 chainId, address tokenContract, uint256 tokenId) = token();
-        if (chainId != block.chainid) return address(0);
+
+        if (chainId != deploymentChainId) return address(0);
 
         return IERC721(tokenContract).ownerOf(tokenId);
     }

src/examples/upgradeable/ERC6551AccountUpgradeable.sol

@@ -36,7 +36,9 @@ contract ERC6551AccountUpgradeable is
     bytes32 internal constant _IMPLEMENTATION_SLOT =
         0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
 
-    uint256 public state;
+    uint256 immutable deploymentChainId = block.chainid;
+
+    bytes32 public state;
 
     receive() external payable {}
 
@@ -51,7 +53,7 @@ contract ERC6551AccountUpgradeable is
     {
         require(_isValidSigner(msg.sender), "Caller is not owner");
         require(_operation == 0, "Only call operations are supported");
-        ++state;
+        state = keccak256(abi.encode(state, msg.data));
         bool success;
         // solhint-disable-next-line avoid-low-level-calls
         (success, _result) = _target.call{value: _value}(_data);
@@ -65,7 +67,7 @@ contract ERC6551AccountUpgradeable is
     function upgrade(address implementation_) external virtual {
         require(_isValidSigner(msg.sender), "Caller is not owner");
         require(implementation_ != address(0), "Invalid implementation address");
-        ++state;
+        state = keccak256(abi.encode(state, msg.data));
         StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = implementation_;
     }
 
@@ -139,7 +141,7 @@ contract ERC6551AccountUpgradeable is
 
     function owner() public view virtual returns (address) {
         (uint256 chainId, address contractAddress, uint256 tokenId) = token();
-        if (chainId != block.chainid) return address(0);
+        if (chainId != deploymentChainId) return address(0);
         return IERC721(contractAddress).ownerOf(tokenId);
     }
 

src/interfaces/IERC6551Account.sol

@@ -32,7 +32,7 @@ interface IERC6551Account {
      *
      * @return The current account state
      */
-    function state() external view returns (uint256);
+    function state() external view returns (bytes32);
 
     /**
      * @dev Returns a magic value indicating whether a given signer is authorized to act on behalf

test/examples/simple/ERC6551Account.t.sol

@@ -49,11 +49,44 @@ contract AccountTest is Test {
 
         vm.deal(account, 1 ether);
 
+        bytes32 expectedState = keccak256(
+            abi.encode(
+                bytes32(0),
+                abi.encodeWithSignature(
+                    "execute(address,uint256,bytes,uint8)", vm.addr(2), 0.5 ether, "", 0
+                )
+            )
+        );
+
         vm.prank(vm.addr(1));
         executableAccountInstance.execute(payable(vm.addr(2)), 0.5 ether, "", 0);
 
         assertEq(account.balance, 0.5 ether);
         assertEq(vm.addr(2).balance, 0.5 ether);
-        assertEq(accountInstance.state(), 1);
+        assertEq(accountInstance.state(), expectedState);
+    }
+
+    function testChainIdPostHardfork() public {
+        nft.mint(vm.addr(1), 1);
+
+        uint256 anvilChainId = block.chainid;
+        uint256 anvilHardforkChainId = anvilChainId + 1;
+        uint256 otherChainId = anvilChainId + 2;
+
+        address anvilAccount =
+            registry.createAccount(address(implementation), 0, anvilChainId, address(nft), 1);
+        address otherChainOnAnvilAccount =
+            registry.createAccount(address(implementation), 0, otherChainId, address(nft), 1);
+
+        assertTrue(anvilAccount != address(0));
+        assertTrue(otherChainOnAnvilAccount != address(0));
+
+        assertEq(ERC6551Account(payable(anvilAccount)).owner(), vm.addr(1));
+        assertEq(ERC6551Account(payable(otherChainOnAnvilAccount)).owner(), address(0));
+
+        vm.chainId(anvilHardforkChainId);
+
+        assertEq(ERC6551Account(payable(anvilAccount)).owner(), vm.addr(1));
+        assertEq(ERC6551Account(payable(otherChainOnAnvilAccount)).owner(), address(0));
     }
 }

test/examples/upgradeable/ERC6551AccountUpgradeable.t.sol

@@ -94,6 +94,15 @@ contract AccountProxyTest is Test {
         IERC6551Account accountInstance = IERC6551Account(payable(account));
         IERC6551Executable executableAccountInstance = IERC6551Executable(account);
 
+        bytes32 expectedState = keccak256(
+            abi.encode(
+                bytes32(0),
+                abi.encodeWithSignature(
+                    "execute(address,uint256,bytes,uint8)", vm.addr(2), 0.5 ether, "", 0
+                )
+            )
+        );
+
         vm.prank(vm.addr(3));
         vm.expectRevert("Caller is not owner");
         executableAccountInstance.execute(payable(vm.addr(2)), 0.5 ether, "", 0);
@@ -103,7 +112,7 @@ contract AccountProxyTest is Test {
 
         assertEq(account.balance, 0.5 ether);
         assertEq(vm.addr(2).balance, 0.5 ether);
-        assertEq(accountInstance.state(), 1);
+        assertEq(accountInstance.state(), expectedState);
     }
 
     function testCannotOwnSelf() public {
@@ -287,14 +296,13 @@ contract AccountProxyTest is Test {
         assertEq(address(uint160(uint256(rawImplementation))), address(0));
 
         // Send ETH to initialize.
-        (bool success, ) = payable(account).call{value: 0}("");
+        (bool success,) = payable(account).call{value: 0}("");
         assertTrue(success);
 
         rawImplementation =
             vm.load(account, 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc);
 
         assertEq(address(uint160(uint256(rawImplementation))), address(implementation));
-
     }
 
     function testERC721Receive() public {
@@ -396,4 +404,28 @@ contract AccountProxyTest is Test {
         vm.expectRevert(InvalidImplementation.selector);
         new ERC6551AccountProxy(address(0));
     }
+
+    function testChainIdPostHardfork() public {
+        nft.mint(vm.addr(1), 1);
+
+        uint256 anvilChainId = block.chainid;
+        uint256 anvilHardforkChainId = anvilChainId + 1;
+        uint256 otherChainId = anvilChainId + 2;
+
+        address anvilAccount =
+            registry.createAccount(address(implementation), 0, anvilChainId, address(nft), 1);
+        address otherChainOnAnvilAccount =
+            registry.createAccount(address(implementation), 0, otherChainId, address(nft), 1);
+
+        assertTrue(anvilAccount != address(0));
+        assertTrue(otherChainOnAnvilAccount != address(0));
+
+        assertEq(ERC6551AccountUpgradeable(payable(anvilAccount)).owner(), vm.addr(1));
+        assertEq(ERC6551AccountUpgradeable(payable(otherChainOnAnvilAccount)).owner(), address(0));
+
+        vm.chainId(anvilHardforkChainId);
+
+        assertEq(ERC6551AccountUpgradeable(payable(anvilAccount)).owner(), vm.addr(1));
+        assertEq(ERC6551AccountUpgradeable(payable(otherChainOnAnvilAccount)).owner(), address(0));
+    }
 }

test/mocks/MockERC6551Account.sol

@@ -8,7 +8,7 @@ import "../../src/interfaces/IERC6551Executable.sol";
 import "../../src/lib/ERC6551AccountLib.sol";
 
 contract MockERC6551Account is IERC165, IERC6551Account, IERC6551Executable {
-    uint256 public state;
+    bytes32 public state;
     bool private _initialized;
 
     receive() external payable {}