Handle template create events processing order during reorgs

packages/codegen/src/templates/indexer-template.handlebars

@@ -635,6 +635,10 @@ export class Indexer implements IndexerInterface {
     return this._baseIndexer.watchContract(address, kind, checkpoint, startingBlock, context);
   }
 
+  async removeContract (address: string, kind: string): Promise<void> {
+    return this._baseIndexer.removeContract(address, kind);
+  }
+
   updateStateStatusMap (address: string, stateStatus: StateStatus): void {
     this._baseIndexer.updateStateStatusMap(address, stateStatus);
   }

packages/graph-node/src/loader.ts

@@ -734,25 +734,13 @@ export const instantiate = async (
         return __newString(dataSource.network);
       },
       'dataSource.create': async (name: number, params: number) => {
-        const [addressStringPtr] = __getArray(params);
+        await handleDataSourceCreate(name, params);
-        const addressString = __getString(addressStringPtr);
-        const contractKind = __getString(name);
-
-        assert(indexer.watchContract);
-        assert(context.block);
-        await indexer.watchContract(utils.getAddress(addressString), contractKind, true, Number(context.block.blockNumber));
       },
       'dataSource.createWithContext': async (name: number, params: number, dataSourceContext: number) => {
-        const [addressStringPtr] = __getArray(params);
-        const addressString = __getString(addressStringPtr);
-        const contractKind = __getString(name);
-
         const contextInstance = await Entity.wrap(dataSourceContext);
         const dbData = await database.fromGraphContext(instanceExports, contextInstance);
 
-        assert(indexer.watchContract);
+        await handleDataSourceCreate(name, params, dbData);
-        assert(context.block);
-        await indexer.watchContract(utils.getAddress(addressString), contractKind, true, Number(context.block.blockNumber), dbData);
       }
     },
     json: {
@@ -786,6 +774,34 @@ export const instantiate = async (
     }
   };
 
+  const handleDataSourceCreate = async (name: number, params: number, dbData?: {[key: string]: any}) => {
+    const [addressStringPtr] = __getArray(params);
+    const addressString = __getString(addressStringPtr);
+    const contractKind = __getString(name);
+
+    assert(context.block);
+    const contractAddress = utils.getAddress(addressString);
+    const watchedContracts = indexer.isContractAddressWatched(contractAddress);
+
+    // If template contract is already watched (incase of reorgs)
+    // Remove from watched contracts and throw error to reprocess block with correct order of template contract events
+    if (
+      watchedContracts &&
+      watchedContracts.some(watchedContract => watchedContract.kind === contractKind)
+    ) {
+      await indexer.removeContract(contractAddress, contractKind);
+      throw new Error(`Template contract ${contractAddress} of kind ${contractKind} already exists; removed from watched contracts`);
+    }
+
+    await indexer.watchContract(
+      contractAddress,
+      contractKind,
+      true,
+      Number(context.block.blockNumber),
+      dbData
+    );
+  };
+
   const instance = await loader.instantiate(source, imports);
   const { exports: instanceExports } = instance;
 

packages/util/src/indexer.ts

@@ -920,6 +920,22 @@ export class Indexer {
     }
   }
 
+  async removeContract (address: string, kind: string): Promise<void> {
+    const dbTx = await this._db.createTransactionRunner();
+
+    try {
+      await this._db.deleteEntitiesByConditions(dbTx, 'contract', { kind, address });
+      this._clearWatchedContracts(
+        watchedContract => watchedContract.kind === kind && watchedContract.address === address
+      );
+    } catch (error) {
+      await dbTx.rollbackTransaction();
+      throw error;
+    } finally {
+      await dbTx.release();
+    }
+  }
+
   cacheContract (contract: ContractInterface): void {
     if (!this._watchedContractsByAddressMap[contract.address]) {
       this._watchedContractsByAddressMap[contract.address] = [];

packages/util/src/types.ts

@@ -217,6 +217,7 @@ export interface IndexerInterface {
   addContracts?: () => Promise<void>
   cacheContract: (contract: ContractInterface) => void;
   watchContract: (address: string, kind: string, checkpoint: boolean, startingBlock: number, context?: any) => Promise<void>
+  removeContract: (address: string, kind: string) => Promise<void>;
   getEntityTypesMap?: () => Map<string, { [key: string]: string }>
   getRelationsMap?: () => Map<any, { [key: string]: any }>
   processInitialState: (contractAddress: string, blockHash: string) => Promise<any>