Forwarder StaticCall and MultiAsset buy support

contracts/exchange-forwarder/contracts/src/MixinAssets.sol

@@ -20,6 +20,7 @@ pragma solidity ^0.5.9;
 
 import "@0x/contracts-utils/contracts/src/LibBytes.sol";
 import "@0x/contracts-utils/contracts/src/LibRichErrors.sol";
+import "@0x/contracts-utils/contracts/src/LibSafeMath.sol";
 import "@0x/contracts-utils/contracts/src/Ownable.sol";
 import "@0x/contracts-erc20/contracts/src/LibERC20Token.sol";
 import "@0x/contracts-erc721/contracts/src/interfaces/IERC721Token.sol";
@@ -35,6 +36,7 @@ contract MixinAssets is
     IAssets
 {
     using LibBytes for bytes;
+    using LibSafeMath for uint256;
 
     /// @dev Withdraws assets from this contract. It may be used by the owner to withdraw assets
     ///      that were accidentally sent to this contract.
@@ -95,7 +97,9 @@ contract MixinAssets is
             _transferERC20Token(assetData, amount);
         } else if (proxyId == IAssetData(address(0)).ERC721Token.selector) {
             _transferERC721Token(assetData, amount);
-        } else {
+        } else if (proxyId == IAssetData(address(0)).MultiAsset.selector) {
+            _transferMultiAsset(assetData, amount);
+        } else if (proxyId != IAssetData(address(0)).StaticCall.selector) {
             LibRichErrors.rrevert(LibForwarderRichErrors.UnsupportedAssetProxyError(
                 proxyId
             ));
@@ -141,4 +145,23 @@ contract MixinAssets is
             tokenId
         );
     }
+
+    function _transferMultiAsset(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal
+    {
+        // solhint-disable indent
+        (uint256[] memory nestedAmounts, bytes[] memory nestedAssetData) = abi.decode(
+            assetData.slice(4, assetData.length),
+            (uint256[], bytes[])
+        );
+        // solhint-enable indent
+
+        uint256 numNestedAssets = nestedAssetData.length;
+        for (uint256 i = 0; i != numNestedAssets; i++) {
+            _transferAssetToSender(nestedAssetData[i], amount.safeMul(nestedAmounts[i]));
+        }
+    }
 }

contracts/exchange-forwarder/contracts/src/MixinExchangeWrapper.sol

@@ -88,9 +88,10 @@ contract MixinExchangeWrapper is
             uint256 makerAssetAcquiredAmount
         )
     {
+        bool noTakerFee = _noTakerFee(order.takerFee, order.takerFeeAssetData);
         // No taker fee or percentage fee
         if (
-            order.takerFee == 0 ||
+            noTakerFee ||
             _areUnderlyingAssetsEqual(order.takerFeeAssetData, order.makerAssetData)
         ) {
             // Attempt to sell the remaining amount of WETH
@@ -105,7 +106,7 @@ contract MixinExchangeWrapper is
 
             // Subtract fee from makerAssetFilledAmount for the net amount acquired.
             makerAssetAcquiredAmount = singleFillResults.makerAssetFilledAmount
-                .safeSub(singleFillResults.takerFeePaid);
+                .safeSub(noTakerFee ? 0 : singleFillResults.takerFeePaid);
 
         // WETH fee
         } else if (_areUnderlyingAssetsEqual(order.takerFeeAssetData, order.takerAssetData)) {
@@ -230,9 +231,10 @@ contract MixinExchangeWrapper is
             uint256 makerAssetAcquiredAmount
         )
     {
+        bool noTakerFee = _noTakerFee(order.takerFee, order.takerFeeAssetData);
         // No taker fee or WETH fee
         if (
-            order.takerFee == 0 ||
+            noTakerFee ||
             _areUnderlyingAssetsEqual(order.takerFeeAssetData, order.takerAssetData)
         ) {
             // Calculate the remaining amount of takerAsset to sell
@@ -251,7 +253,7 @@ contract MixinExchangeWrapper is
 
             // WETH is also spent on the protocol and taker fees, so we add it here.
             wethSpentAmount = singleFillResults.takerAssetFilledAmount
-                .safeAdd(singleFillResults.takerFeePaid)
+                .safeAdd(noTakerFee ? 0 : singleFillResults.takerFeePaid)
                 .safeAdd(singleFillResults.protocolFeePaid);
 
             makerAssetAcquiredAmount = singleFillResults.makerAssetFilledAmount;
@@ -419,7 +421,7 @@ contract MixinExchangeWrapper is
         return fillResults;
     }
 
-    /// @dev Fills the input ExchangeV3 order. 
+    /// @dev Fills the input ExchangeV3 order.
     ///      Returns false if the transaction would otherwise revert.
     /// @param order Order struct containing order specifications.
     /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
@@ -480,7 +482,7 @@ contract MixinExchangeWrapper is
             address token2 = assetData2.readAddress(16);
             return (token1 == token2);
         } else {
-            return false;
+            return assetData1.equals(assetData2);
         }
     }
 
@@ -494,4 +496,24 @@ contract MixinExchangeWrapper is
     {
         return order.makerFeeAssetData.length > 3 && order.makerFeeAssetData.readBytes4(0) == EXCHANGE_V2_ORDER_ID;
     }
+
+    /// @dev Checks whether one asset is effectively equal to another asset.
+    ///      This is the case if they have the same ERC20Proxy/ERC20BridgeProxy asset data, or if
+    ///      one is the ERC20Bridge equivalent of the other.
+    /// @param takerFee Byte array encoded for the takerFee asset proxy.
+    /// @param takerFeeAssetData Byte array encoded for the maker asset proxy.
+    /// @return Whether or not the underlying assets are equal.
+    function _noTakerFee(
+        uint256 takerFee,
+        bytes memory takerFeeAssetData
+    )
+        internal
+        pure
+        returns (bool)
+    {
+        return (
+            takerFee == 0 ||
+            takerFeeAssetData.readBytes4(0) == IAssetData(address(0)).StaticCall.selector
+        );
+    }
 }