fix: prefer multipart/mixed content-type for defer/stream operations (#2676)

Author: n1ru4l

.changeset/polite-rats-hunt.md

@@ -0,0 +1,5 @@
+---
+'graphql-yoga': patch
+---
+
+Prefer `content-type: multipart/mixed` over `content-type: text/event-stream` when the client sends `accept: text/event-stream, multipart/mixed`.

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

@@ -1,4 +1,4 @@
-import { createSchema, createYoga } from '../src/index.js'
+import { Repeater, createSchema, createYoga } from '../src/index.js'
 import { createClient } from 'graphql-sse'
 
 describe('GraphQL over SSE', () => {
@@ -182,6 +182,46 @@ describe('GraphQL over SSE', () => {
         "
       `)
     })
+
+    it('accept: application/graphql-response+json, application/json,  multipart/mixed, text/event-stream', async () => {
+      const yoga = createYoga({
+        schema: createSchema({
+          typeDefs: /* GraphQL */ `
+            type Query {
+              hi: [String]
+            }
+
+            type Subscription {
+              hi: String!
+            }
+          `,
+          resolvers: {
+            Query: {
+              hi: () => 'hi',
+            },
+            Subscription: {
+              hi: {
+                subscribe: () => new Repeater((push) => push({ hi: 'hi' })),
+              },
+            },
+          },
+        }),
+        plugins: [],
+      })
+
+      const response = await yoga.fetch('http://yoga/graphql', {
+        method: 'POST',
+        headers: {
+          'content-type': 'application/json',
+          accept:
+            'application/graphql-response+json, application/json, multipart/mixed, text/event-stream',
+        },
+        body: JSON.stringify({ query: 'subscription { hi }' }),
+      })
+
+      expect(response.status).toEqual(200)
+      expect(response.headers.get('content-type')).toEqual('text/event-stream')
+    })
   })
 
   it.todo('Single connections mode')

packages/graphql-yoga/src/plugins/useResultProcessor.ts

@@ -43,6 +43,7 @@ export function useResultProcessors(opts: SSEProcessorOptions): Plugin {
   const sse = getSSEProcessorConfig(opts)
   const defaultList = [sse, multipart, regular]
   const subscriptionList = [multipart, sse, regular]
+
   return {
     onSubscribe({ args: { contextValue } }) {
       if (contextValue.request) {
@@ -61,8 +62,9 @@ export function useResultProcessors(opts: SSEProcessorOptions): Plugin {
         : defaultList
       const requestMediaTypes = getMediaTypesForRequestInOrder(request)
       const isAsyncIterableResult = isAsyncIterable(result)
-      for (const requestMediaType of requestMediaTypes) {
-        for (const resultProcessorConfig of processorConfigList) {
+
+      for (const resultProcessorConfig of processorConfigList) {
+        for (const requestMediaType of requestMediaTypes) {
           if (isAsyncIterableResult && !resultProcessorConfig.asyncIterables) {
             continue
           }

packages/plugins/defer-stream/__tests__/defer-stream.spec.ts

@@ -458,6 +458,42 @@ describe('Defer/Stream', () => {
         'multipart/mixed; boundary="-"',
       )
     })
+
+    it('accept: application/graphql-response+json, application/json, text/event-stream, multipart/mixed', async () => {
+      const yoga = createYoga({
+        schema: createSchema({
+          typeDefs: /* GraphQL */ `
+            type Query {
+              hi: [String]
+            }
+          `,
+          resolvers: {
+            Query: {
+              hi: () =>
+                new Repeater(async (push, stop) => {
+                  await push('A')
+                  stop()
+                }),
+            },
+          },
+        }),
+        plugins: [useDeferStream()],
+      })
+
+      const response = await yoga.fetch('http://yoga/graphql', {
+        method: 'POST',
+        headers: {
+          'content-type': 'application/json',
+          accept:
+            'application/graphql-response+json, application/json, text/event-stream, multipart/mixed',
+        },
+        body: JSON.stringify({ query: '{ hi @stream }' }),
+      })
+      expect(response.status).toEqual(200)
+      expect(response.headers.get('content-type')).toEqual(
+        'multipart/mixed; boundary="-"',
+      )
+    })
   })
 
   describe('@graphql-tools/buildHTTPExecutor', () => {