feat: variable batching

Author: ardatan

.changeset/quiet-owls-occur.md

@@ -0,0 +1,5 @@
+---
+'graphql-yoga': minor
+---
+
+Support variable batching

packages/graphql-yoga/__tests__/batching.spec.ts

@@ -7,12 +7,14 @@ describe('Batching', () => {
       type Query {
         hello: String
         bye: String
+        greetings(name: String!): String!
       }
     `,
     resolvers: {
       Query: {
         hello: () => 'hello',
         bye: () => 'bye',
+        greetings: (_root, { name }) => `hello, ${name}`,
       },
     },
   });
@@ -352,4 +354,32 @@ describe('Batching', () => {
     expect(contexts[0]!.i).toEqual(1);
     expect(contexts[1]!.i).toEqual(2);
   });
+  it('variable batching', async () => {
+    const yoga = createYoga({
+      schema,
+      batching: {},
+    });
+    const query = /* GraphQL */ `
+      query ($name: String!) {
+        greetings(name: $name)
+      }
+    `;
+    const res = await yoga.fetch('http://yoga/graphql', {
+      method: 'POST',
+      headers: {
+        accept: 'application/graphql-response+json',
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify({
+        query,
+        variables: [{ name: 'Alice' }, { name: 'Bob' }, { name: 'Charlie' }],
+      }),
+    });
+    const result = await res.json();
+    expect(result).toEqual([
+      { data: { greetings: 'hello, Alice' } },
+      { data: { greetings: 'hello, Bob' } },
+      { data: { greetings: 'hello, Charlie' } },
+    ]);
+  });
 });

packages/graphql-yoga/src/server.ts

@@ -83,6 +83,7 @@ import {
   YogaMaskedErrorOpts,
 } from './types.js';
 import { maskError } from './utils/mask-error.js';
+import { processBatchedParams } from './utils/process-batched-params.js';
 
 /**
  * Configuration options for the server
@@ -666,6 +667,7 @@ export class YogaServer<
           if (response) {
             return response;
           }
+          requestParserResult = processBatchedParams(requestParserResult!);
           const getResultForParams = this.instrumentation?.operation
             ? (payload: { request: Request; params: GraphQLParams }, context: any) => {
                 const instrumented = getInstrumented({ context, request: payload.request });

packages/graphql-yoga/src/utils/process-batched-params.ts

@@ -0,0 +1,16 @@
+import { GraphQLParams } from '../types.js';
+
+export function processBatchedParams(
+  params: GraphQLParams | GraphQLParams[],
+): GraphQLParams | GraphQLParams[] {
+  if (Array.isArray(params)) {
+    return params.flatMap(param => processBatchedParams(param));
+  }
+  if (Array.isArray(params.variables)) {
+    return params.variables.map(variables => ({
+      ...params,
+      variables,
+    }));
+  }
+  return params;
+}