fix(batch-delegate): memoize the key arguments correctly (#396)

.changeset/wicked-islands-march.md

@@ -0,0 +1,65 @@
+---
+'@graphql-tools/batch-delegate': patch
+---
+
+Memoize the key arguments correctly;
+
+With the following schema and resolvers, `userById` should batch all the requests to `usersByIds`;
+
+```ts
+{
+      typeDefs: /* GraphQL */ `
+        type User {
+          id: ID!
+          email: String!
+        }
+        type Query {
+          userById(id: ID!): User
+          usersByIds(ids: [ID!]): [User]
+        }
+      `,
+      resolvers: {
+        Query: {
+          usersByIds: (_root, args) => {
+            return args.ids.map((id: string) => users.find((user) => user.id === id));
+          },
+          userById: (root, args, context, info) => {
+            return batchDelegateToSchema({
+              schema: userSubschema,
+              fieldName: 'usersByIds',
+              key: args.id,
+              rootValue: root,
+              context,
+              info,
+            })
+          },
+        },
+      },
+    }
+```
+
+This query should batch all the requests to `usersByIds`:
+
+```graphql
+{
+  userById(id: "1") {
+    id
+    email
+  }
+  userById(id: "2") {
+    id
+    email
+  }
+}
+```
+
+The delegation request should be;
+
+```graphql
+{
+  usersByIds(ids: ["1", "2"]) {
+    id
+    email
+  }
+}
+```

packages/batch-delegate/src/batchDelegateToSchema.ts

@@ -1,8 +1,8 @@
 import { getLoader } from './getLoader.js';
 import { BatchDelegateOptions } from './types.js';
 
-export function batchDelegateToSchema<TContext = any>(
-  options: BatchDelegateOptions<TContext>,
+export function batchDelegateToSchema<TContext = any, K = any, V = any, C = K>(
+  options: BatchDelegateOptions<TContext, K, V, C>,
 ): any {
   const key = options.key;
   if (key == null) {

packages/batch-delegate/src/getLoader.ts

@@ -14,9 +14,10 @@ import DataLoader from 'dataloader';
 import { getNamedType, GraphQLList, GraphQLSchema, print } from 'graphql';
 import { BatchDelegateOptions } from './types.js';
 
+const DEFAULT_ARGS_FROM_KEYS = (keys: ReadonlyArray<any>) => ({ ids: keys });
+
 function createBatchFn<K = any>(options: BatchDelegateOptions) {
-  const argsFromKeys =
-    options.argsFromKeys ?? ((keys: ReadonlyArray<K>) => ({ ids: keys }));
+  const argsFromKeys = options.argsFromKeys ?? DEFAULT_ARGS_FROM_KEYS;
   const fieldName = options.fieldName ?? options.info.fieldName;
   const { valuesFromResults, lazyOptionsFn } = options;
 
@@ -103,6 +104,8 @@ export function getLoader<K = any, V = any, C = K>(
     fieldNodes = info.fieldNodes[0] && getActualFieldNodes(info.fieldNodes[0]),
     selectionSet = fieldNodes?.[0]?.selectionSet,
     returnType = info.returnType,
+    argsFromKeys = DEFAULT_ARGS_FROM_KEYS,
+    key,
   } = options;
   const loaders = getLoadersMap<K, V, C>(context ?? GLOBAL_CONTEXT, schema);
 
@@ -119,7 +122,11 @@ export function getLoader<K = any, V = any, C = K>(
 
   const fieldNode = fieldNodes?.[0];
   if (fieldNode?.arguments) {
-    cacheKey += fieldNode.arguments.map((arg) => memoizedPrint(arg)).join(',');
+    const args = argsFromKeys([key]);
+    cacheKey += fieldNode.arguments
+      .filter((arg) => arg.name.value in args)
+      .map((arg) => memoizedPrint(arg))
+      .join(',');
   }
 
   let loader = loaders.get(cacheKey);

packages/batch-delegate/tests/basic.example.test.ts

@@ -102,7 +102,6 @@ describe('batch delegation within basic stitching example', () => {
     const chirps: any = result.data!['trendingChirps'];
     expect(chirps[0].chirpedAtUser.email).not.toBe(null);
   });
-
   test('works with key arrays', async () => {
     let numCalls = 0;
 
@@ -216,7 +215,6 @@ describe('batch delegation within basic stitching example', () => {
       ],
     });
   });
-
   test('works with keys passed to lazyOptionsFn', async () => {
     let numCalls = 0;