Expose the current request query path to the "willSendRequest" and "d…

…idReceiveResponse" hooks (#2384)

This commit exposes the `path` to a given subgraph fetch in the hooks of `RemoteGraphQLDataSource`.

.changeset/flat-books-sin.md

@@ -0,0 +1,5 @@
+---
+"@apollo/gateway": patch
+---
+
+Exposes, for each subgraph request, the path in the overall gateway operation at which that subgraph request gets inserted. This path is now available as the pathInIncomingRequest field in the arguments of RemoteGraphQLDataSource.willSendRequest and RemoteGraphQLDataSource.didReceiveResponse.

gateway-js/src/datasources/RemoteGraphQLDataSource.ts

@@ -1,6 +1,7 @@
 import { isObject } from '../utilities/predicates';
 import { GraphQLDataSource, GraphQLDataSourceProcessOptions, GraphQLDataSourceRequestKind } from './types';
 import { createHash } from '@apollo/utils.createhash';
+import { ResponsePath } from '@apollo/query-planner';
 import { parseCacheControlHeader } from './parseCacheControlHeader';
 import fetcher from 'make-fetch-happen';
 import { Headers as NodeFetchHeaders, Request as NodeFetchRequest } from 'node-fetch';
@@ -67,6 +68,11 @@ export class RemoteGraphQLDataSource<
     options: GraphQLDataSourceProcessOptions<TContext>,
   ): Promise<GatewayGraphQLResponse> {
     const { request, context: originalContext } = options;
+    const pathInIncomingRequest =
+      options.kind === GraphQLDataSourceRequestKind.INCOMING_OPERATION
+        ? options.pathInIncomingRequest
+        : undefined;
+
     // Deal with a bit of a hairy situation in typings: when doing health checks
     // and schema checks we always pass in `{}` as the context even though it's
     // not really guaranteed to be a `TContext`, and then we pass it to various
@@ -143,6 +149,7 @@ export class RemoteGraphQLDataSource<
           request: requestWithoutQuery,
           context,
           overallCachePolicy,
+          pathInIncomingRequest
         });
       }
     }
@@ -160,6 +167,7 @@ export class RemoteGraphQLDataSource<
       request: requestWithQuery,
       context,
       overallCachePolicy,
+      pathInIncomingRequest
     });
   }
 
@@ -226,15 +234,17 @@ export class RemoteGraphQLDataSource<
     request,
     context,
     overallCachePolicy,
+    pathInIncomingRequest
   }: {
     response: GatewayGraphQLResponse;
     request: GatewayGraphQLRequest;
     context: TContext;
     overallCachePolicy: GatewayCachePolicy | null;
+    pathInIncomingRequest?: ResponsePath
   }): Promise<GatewayGraphQLResponse> {
     const processedResponse =
       typeof this.didReceiveResponse === 'function'
-        ? await this.didReceiveResponse({ response, request, context })
+        ? await this.didReceiveResponse({ response, request, context, pathInIncomingRequest })
         : response;
 
     if (overallCachePolicy) {
@@ -266,7 +276,7 @@ export class RemoteGraphQLDataSource<
   public didReceiveResponse?(
     requestContext: Required<
       Pick<GatewayGraphQLRequestContext<TContext>, 'request' | 'response' | 'context'>
-    >,
+    > & { pathInIncomingRequest?: ResponsePath }
   ): GatewayGraphQLResponse | Promise<GatewayGraphQLResponse>;
 
   public didEncounterError(

gateway-js/src/datasources/types.ts

@@ -1,3 +1,4 @@
+import { ResponsePath } from '@apollo/query-planner';
 import { GatewayGraphQLResponse, GatewayGraphQLRequestContext } from '@apollo/server-gateway-interface';
 
 export interface GraphQLDataSource<
@@ -47,6 +48,12 @@ export type GraphQLDataSourceProcessOptions<
        * this will increase the memory used by the gateway query plan cache.
        */
       document?: GatewayGraphQLRequestContext<TContext>['document'];
+
+      /**
+      * The path in the overall gateway operation at which that subgraph request gets inserted.
+      * Please note that this could be set to `undefined` when the path is not available, or set to an empty array for top-level fetch operations.
+      */
+      pathInIncomingRequest?: ResponsePath;
     }
   | {
       kind:

gateway-js/src/executeQueryPlan.ts

@@ -489,6 +489,7 @@ async function executeFetch(
       incomingRequestContext: context.requestContext,
       context: context.requestContext.context,
       document: fetch.operationDocumentNode,
+      pathInIncomingRequest: currentCursor.path
     });
 
     if (response.errors) {