From c5f6ebee188e35a4e7fc8b9363d04ca90e4f31ee Mon Sep 17 00:00:00 2001
From: Jacob Evans <jacob@dekz.net>
Date: Fri, 10 May 2019 16:09:09 +0200
Subject: [PATCH] Mutate ERC20 ABI to handle WETH Deposit and Withdrawl

---
 .../collision_resistant_abi_decoder.ts          | 17 +++++++----------
 .../src/order_watcher/order_watcher.ts          | 15 +++++++++++++--
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/packages/order-watcher/src/order_watcher/collision_resistant_abi_decoder.ts b/packages/order-watcher/src/order_watcher/collision_resistant_abi_decoder.ts
index 52f28cd4a3..2ea7969470 100644
--- a/packages/order-watcher/src/order_watcher/collision_resistant_abi_decoder.ts
+++ b/packages/order-watcher/src/order_watcher/collision_resistant_abi_decoder.ts
@@ -26,19 +26,16 @@ export class CollisionResistanceAbiDecoder {
         this._restAbiDecoder = new AbiDecoder(abis);
     }
     public tryToDecodeLogOrNoop<ArgsType extends DecodedLogArgs>(log: LogEntry): LogWithDecodedArgs<ArgsType> | RawLog {
-        let maybeDecodedLog = log;
         if (this._knownERC20Tokens.has(log.address)) {
-            maybeDecodedLog = this._erc20AbiDecoder.tryToDecodeLogOrNoop(log);
+            const maybeDecodedERC20Log = this._erc20AbiDecoder.tryToDecodeLogOrNoop(log);
+            return maybeDecodedERC20Log;
         } else if (this._knownERC721Tokens.has(log.address)) {
-            maybeDecodedLog = this._erc721AbiDecoder.tryToDecodeLogOrNoop(log);
+            const maybeDecodedERC721Log = this._erc721AbiDecoder.tryToDecodeLogOrNoop(log);
+            return maybeDecodedERC721Log;
+        } else {
+            const maybeDecodedLog = this._restAbiDecoder.tryToDecodeLogOrNoop(log);
+            return maybeDecodedLog;
         }
-        // Fall back to the supplied ABIs for decoding if the ERC20/ERC721 decoding fails
-        // This ensures we hit events like Deposit and Withdraw given WETH can be a known ERC20Token
-        const isLogDecoded = ((maybeDecodedLog as any) as LogWithDecodedArgs<DecodedLogArgs>).event !== undefined;
-        if (!isLogDecoded) {
-            maybeDecodedLog = this._restAbiDecoder.tryToDecodeLogOrNoop(log);
-        }
-        return maybeDecodedLog;
     }
     // Hints the ABI decoder that a particular token address is ERC20 and events from it should be decoded as ERC20 events
     public addERC20Token(address: string): void {
diff --git a/packages/order-watcher/src/order_watcher/order_watcher.ts b/packages/order-watcher/src/order_watcher/order_watcher.ts
index 78c619859f..c298cbcac4 100644
--- a/packages/order-watcher/src/order_watcher/order_watcher.ts
+++ b/packages/order-watcher/src/order_watcher/order_watcher.ts
@@ -119,10 +119,20 @@ export class OrderWatcher {
         };
 
         this._provider = provider;
+        const wethDepositEvent = _.find(
+            artifacts.WETH9.compilerOutput.abi,
+            item => item.type === 'event' && item.name === 'Deposit',
+        );
+        const wethWithdrawEvent = _.find(
+            artifacts.WETH9.compilerOutput.abi,
+            item => item.type === 'event' && item.name === 'Withdrawal',
+        );
+        // Combine ERC20 and WETH events into a single ABI. This is used as the default ERC20 ABI when decoding
+        const combinedWETHERC20Abi = [...artifacts.ERC20Token.compilerOutput.abi, wethDepositEvent, wethWithdrawEvent];
         this._collisionResistantAbiDecoder = new CollisionResistanceAbiDecoder(
-            artifacts.ERC20Token.compilerOutput.abi,
+            combinedWETHERC20Abi,
             artifacts.ERC721Token.compilerOutput.abi,
-            [artifacts.WETH9.compilerOutput.abi, artifacts.Exchange.compilerOutput.abi],
+            [artifacts.Exchange.compilerOutput.abi],
         );
         const contractWrappers = new ContractWrappers(provider, {
             networkId,
@@ -150,6 +160,7 @@ export class OrderWatcher {
         this._cleanupJobInterval = config.cleanupJobIntervalMs;
         const zrxTokenAddress = assetDataUtils.decodeERC20AssetData(orderFilledCancelledFetcher.getZRXAssetData())
             .tokenAddress;
+        this._collisionResistantAbiDecoder.addERC20Token(zrxTokenAddress);
         this._dependentOrderHashesTracker = new DependentOrderHashesTracker(zrxTokenAddress);
     }
     /**