Support 'application/graphql-response+json' (#1616)

* Support 'application/graphql-response+json'

* Bring back the old behavior

* Fix the order

* Go

Author: ardatan

.changeset/tall-paws-do.md

@@ -0,0 +1,5 @@
+---
+'graphql-yoga': patch
+---
+
+Support `application/graphql-response+json`

packages/graphql-yoga/__tests__/accept-header.spec.ts

@@ -204,4 +204,57 @@ describe('accept header', () => {
     })
     expect(response.status).toEqual(406)
   })
+
+  it('server returns "application/graphql-response+json" content-type if accept header is "application/graphql-response+json"', async () => {
+    const yoga = createYoga({
+      schema: createSchema({
+        typeDefs: /* GraphQL */ `
+          type Query {
+            ping: String
+          }
+        `,
+        resolvers: {
+          Query: { ping: () => 'pong' },
+        },
+      }),
+    })
+
+    const response = await yoga.fetch(`http://yoga/graphql?query=query{ping}`, {
+      headers: {
+        accept: 'application/graphql-response+json',
+      },
+    })
+    expect(response.headers.get('content-type')).toEqual(
+      'application/graphql-response+json',
+    )
+    const result = await response.json()
+    expect(result).toEqual({ data: { ping: 'pong' } })
+  })
+
+  it('server returns "application/graphql-response+json" content-type if accept header includes both "application/graphql-response+json" and "application/json"', async () => {
+    const yoga = createYoga({
+      schema: createSchema({
+        typeDefs: /* GraphQL */ `
+          type Query {
+            ping: String
+          }
+        `,
+        resolvers: {
+          Query: { ping: () => 'pong' },
+        },
+      }),
+    })
+
+    const response = await yoga.fetch(`http://yoga/graphql?query=query{ping}`, {
+      headers: {
+        accept:
+          'application/graphql-response+json; charset=utf-8, application/json; charset=utf-8',
+      },
+    })
+    expect(response.headers.get('content-type')).toEqual(
+      'application/graphql-response+json',
+    )
+    const result = await response.json()
+    expect(result).toEqual({ data: { ping: 'pong' } })
+  })
 })

packages/graphql-yoga/src/plugins/resultProcessor/regular.ts

@@ -12,14 +12,18 @@ export function isRegularResult(
   if (!isAsyncIterable(result)) {
     const acceptHeader = request.headers.get('accept')
     if (acceptHeader && !acceptHeader.includes('*/*')) {
-      if (acceptHeader.includes('application/json')) {
-        acceptHeaderByResult.set(result, 'application/json')
+      if (acceptHeader.includes('application/graphql-response+json')) {
+        acceptHeaderByResult.set(result, 'application/graphql-response+json')
         return true
       }
       if (acceptHeader.includes('application/graphql+json')) {
         acceptHeaderByResult.set(result, 'application/graphql+json')
         return true
       }
+      if (acceptHeader.includes('application/json')) {
+        acceptHeaderByResult.set(result, 'application/json')
+        return true
+      }
       // If there is an accept header but this processer doesn't support, reject
       return false
     }