fix: emit correct transfer and approval events (#194) (#215)

Signed-off-by: Mariusz Jasuwienas <[email protected]>

contracts/HtsSystemContract.sol

@@ -10,7 +10,7 @@ import {SetTokenInfo} from "./SetTokenInfo.sol";
 
 address constant HTS_ADDRESS = address(0x167);
 
-contract HtsSystemContract is IHederaTokenService, IERC20Events, IERC721Events {
+contract HtsSystemContract is IHederaTokenService {
 
     /**
      * The slot's value contains the next token ID to use when a token is being created.
@@ -574,7 +574,7 @@ contract HtsSystemContract is IHederaTokenService, IERC20Events, IERC721Events {
                 address to = address(bytes20(msg.data[72:92]));
                 uint256 amount = uint256(bytes32(msg.data[92:124]));
                 _approve(from, to, amount);
-                emit Approval(from, to, amount);
+                emit IERC20Events.Approval(from, to, amount);
                 return abi.encode(true);
             }
             if (selector == this.approveNFT.selector) {
@@ -670,7 +670,7 @@ contract HtsSystemContract is IHederaTokenService, IERC20Events, IERC721Events {
             uint256 amount = uint256(bytes32(msg.data[60:92]));
             address owner = msg.sender;
             _approve(owner, spender, amount);
-            emit Approval(owner, spender, amount);
+            emit IERC20Events.Approval(owner, spender, amount);
             return abi.encode(true);
         }
         return _redirectForHRC719(selector);
@@ -844,7 +844,7 @@ contract HtsSystemContract is IHederaTokenService, IERC20Events, IERC721Events {
         require(from != address(0), "hts: invalid sender");
         require(to != address(0), "hts: invalid receiver");
         _update(from, to, amount);
-        emit Transfer(from, to, amount);
+        emit IERC20Events.Transfer(from, to, amount);
     }
 
     function _transferNFT(address sender, address from, address to, uint256 serialId) private {
@@ -872,7 +872,7 @@ contract HtsSystemContract is IHederaTokenService, IERC20Events, IERC721Events {
 
         // Set the new owner
         assembly { sstore(slot, to) }
-        emit Transfer(from, to, serialId);
+        emit IERC721Events.Transfer(from, to, serialId);
     }
 
     function _update(address from, address to, uint256 amount) public {
@@ -917,8 +917,7 @@ contract HtsSystemContract is IHederaTokenService, IERC20Events, IERC721Events {
         bytes32 slot = _getApprovedSlot(uint32(serialId));
         address newApproved = isApproved ? spender : address(0);
         assembly { sstore(slot, newApproved) }
-
-        emit Approval(owner, spender, serialId);
+        emit IERC721Events.Approval(owner, spender, serialId);
     }
 
     /**
@@ -939,6 +938,6 @@ contract HtsSystemContract is IHederaTokenService, IERC20Events, IERC721Events {
         require(operator != address(0) && operator != sender, "setApprovalForAll: invalid operator");
         bytes32 slot = _isApprovedForAllSlot(sender, operator);
         assembly { sstore(slot, approved) }
-        emit ApprovalForAll(sender, operator, approved);
+        emit IERC721Events.ApprovalForAll(sender, operator, approved);
     }
 }

contracts/IERC20.sol

@@ -52,7 +52,7 @@ interface IERC20 {
 
     /**
      * @dev Returns the value of tokens owned by `account`.
-     */    
+     */
     function balanceOf(address account) external view returns (uint256);
 
     /**

contracts/IERC721.sol

@@ -2,9 +2,34 @@
 pragma solidity ^0.8.0;
 
 /**
+ * These events should be emitted by `transfer|transferFrom`, `approve` and `setApprovalForAll` respectively.
+ *
  * See https://ethereum.org/en/developers/docs/standards/tokens/erc-721/#events for more information.
  */
 interface IERC721Events {
+    /**
+     * @dev Emitted when ownership of any NFT changes by any mechanism.
+     * This event emits when NFTs are created (`from` == 0) and destroyed (`to` == 0).
+     * Otherwise, it indicates that the token with ID {tokenId} was transferred from {from} to {to},
+     * where {from} represents the previous owner of the token, not the approved spender.
+     *
+     * Exception: during contract creation, any number of NFTs may be created and assigned without emitting Transfer.
+     *
+     * At the time of any transfer, the approved address for that NFT (if any) is reset to none.
+     */
+    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
+
+    /**
+     * @dev Emitted when the approved address for an NFT is changed or reaffirmed from {from} to {to} address.
+     * The zero {to} address indicates there will be no approved address.
+     * Additionally the approved address for that NFT (if any) is reset to none.
+     */
+    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
+
+    /**
+     * @dev Emitted when an operator {operator} is enabled or disabled {approved}
+     * for an owner {owner}. The operator {operator} can than manage all NFTs of the owner {owner}.
+     */
     event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
 }
 
@@ -45,6 +70,8 @@ interface IERC721 {
      *
      * Requirements:
      * - `serialId` must exist.
+     *
+     * This value changes when {approve} or {transferFrom} are called.
      */
     function ownerOf(uint256 serialId) external view returns (address);
 

test/ERC721.t.sol

@@ -4,10 +4,9 @@ pragma solidity ^0.8.0;
 import {HtsSystemContract} from "../contracts/HtsSystemContract.sol";
 import {Test, console} from "forge-std/Test.sol";
 import {IERC721, IERC721Events} from "../contracts/IERC721.sol";
-import {IERC20Events} from "../contracts/IERC20.sol";
 import {TestSetup} from "./lib/TestSetup.sol";
 
-contract ERC721TokenTest is Test, TestSetup, IERC721Events, IERC20Events {
+contract ERC721TokenTest is Test, TestSetup, IERC721Events {
 
     function setUp() external {
         setUpMockStorageForNonFork();

test/HTS.t.sol

@@ -686,7 +686,7 @@ contract HTSTest is Test, TestSetup {
         uint256 serialId = 1;
         vm.startPrank(CFNFTFF_TREASURY);
         vm.expectEmit(CFNFTFF);
-        emit IERC20Events.Transfer(CFNFTFF_TREASURY, to, serialId);
+        emit IERC721Events.Transfer(CFNFTFF_TREASURY, to, serialId);
         IHederaTokenService(HTS_ADDRESS).transferNFT(CFNFTFF, CFNFTFF_TREASURY, to, int64(int256(serialId)));
         vm.stopPrank();
         assertEq(IERC721(CFNFTFF).ownerOf(serialId), to);
@@ -697,7 +697,7 @@ contract HTSTest is Test, TestSetup {
         uint256 serialId = 1;
         vm.startPrank(CFNFTFF_TREASURY);
         vm.expectEmit(CFNFTFF);
-        emit IERC20Events.Transfer(CFNFTFF_TREASURY, to, serialId);
+        emit IERC721Events.Transfer(CFNFTFF_TREASURY, to, serialId);
         IHederaTokenService(HTS_ADDRESS).transferFromNFT(CFNFTFF, CFNFTFF_TREASURY, to, serialId);
         vm.stopPrank();
         assertEq(IERC721(CFNFTFF).ownerOf(serialId), to);
@@ -770,7 +770,7 @@ contract HTSTest is Test, TestSetup {
         to[0] = makeAddr("recipient");
         vm.startPrank(CFNFTFF_TREASURY);
         vm.expectEmit(CFNFTFF);
-        emit IERC20Events.Transfer(CFNFTFF_TREASURY, to[0], serialId[0]);
+        emit IERC721Events.Transfer(CFNFTFF_TREASURY, to[0], serialId[0]);
         IHederaTokenService(HTS_ADDRESS).transferNFT(CFNFTFF, from[0], to[0], int64(int256(serialId[0])));
         vm.stopPrank();
         assertEq(IERC721(CFNFTFF).ownerOf(serialId[0]), to[0]);
@@ -811,7 +811,7 @@ contract HTSTest is Test, TestSetup {
         assertNotEq(IERC721(token).getApproved(1), newSpender);
         vm.prank(CFNFTFF_TREASURY);
         vm.expectEmit(token);
-        emit IERC20Events.Approval(CFNFTFF_TREASURY, newSpender, 1);
+        emit IERC721Events.Approval(CFNFTFF_TREASURY, newSpender, 1);
         int64 responseCodeApprove = IHederaTokenService(HTS_ADDRESS).approveNFT(token, newSpender, 1);
         assertEq(responseCodeApprove, HederaResponseCodes.SUCCESS);
         assertEq(IERC721(token).getApproved(1), newSpender);