feat(server): Define execution/subscription context in creation opt…

…ions

Closes enisdenjo#13

src/server.ts

@@ -52,6 +52,14 @@ export interface ServerOptions {
    * from the `onSubscribe` callback.
    */
   schema?: GraphQLSchema;
+  /**
+   * A value which is provided to every resolver and holds
+   * important contextual information like the currently
+   * logged in user, or access to a database.
+   * Related operation context value will be injected to the
+   * `ExecutionArgs` BEFORE the `onSubscribe` callback.
+   */
+  context?: SubscriptionArgs['contextValue'];
   /**
    * The GraphQL root fields or resolvers to go
    * alongside the schema. Learn more about them
@@ -213,6 +221,7 @@ export function createServer(
 ): Server {
   const {
     schema,
+    context,
     roots,
     execute,
     subscribe,
@@ -403,6 +412,7 @@ export function createServer(
             }
 
             let execArgsMaybeSchema: Optional<ExecutionArgs, 'schema'> = {
+              contextValue: context,
               schema,
               operationName: operation.operationName,
               document,

src/tests/fixtures/simple.ts

@@ -33,6 +33,14 @@ export const schema = new GraphQLSchema({
   subscription: new GraphQLObjectType({
     name: 'Subscription',
     fields: {
+      greetings: {
+        type: new GraphQLNonNull(GraphQLString),
+        subscribe: async function* () {
+          for (const hi of ['Hi', 'Bonjour', 'Hola', 'Ciao', 'Zdravo']) {
+            yield { greetings: hi };
+          }
+        },
+      },
       becameHappy: {
         type: personType,
         args: {

src/tests/server.ts

@@ -1,5 +1,5 @@
 import WebSocket from 'ws';
-import { parse, buildSchema } from 'graphql';
+import { parse, buildSchema, execute, subscribe } from 'graphql';
 import { GRAPHQL_TRANSPORT_WS_PROTOCOL } from '../protocol';
 import { MessageType, parseMessage, stringifyMessage } from '../message';
 import { startServer, url, schema, pubsub } from './fixtures/simple';
@@ -998,3 +998,75 @@ it('should use the provided roots as resolvers', async () => {
   });
   expect(nextFn).toBeCalledTimes(3);
 });
+
+it('should pass in the context value from the config', async () => {
+  const context = {};
+
+  const executeFn = jest.fn((args) => execute(args));
+  const subscribeFn = jest.fn((args) => subscribe(args));
+
+  await makeServer({
+    context,
+    execute: executeFn,
+    subscribe: subscribeFn,
+  });
+
+  const client = new WebSocket(url, GRAPHQL_TRANSPORT_WS_PROTOCOL);
+  await new Promise((resolve) => {
+    client.onopen = () => {
+      client.send(
+        stringifyMessage<MessageType.ConnectionInit>({
+          type: MessageType.ConnectionInit,
+        }),
+      );
+    };
+    client.onmessage = ({ data }) => {
+      const message = parseMessage(data);
+      if (message.type === MessageType.ConnectionAck) {
+        resolve();
+      }
+    };
+  });
+
+  await new Promise((resolve) => {
+    client.send(
+      stringifyMessage<MessageType.Subscribe>({
+        id: '1',
+        type: MessageType.Subscribe,
+        payload: {
+          query: `{ getValue }`,
+        },
+      }),
+    );
+    client.onmessage = ({ data }) => {
+      const message = parseMessage(data);
+      if (message.type === MessageType.Next && message.id === '1') {
+        resolve();
+      }
+    };
+  });
+
+  expect(executeFn).toBeCalled();
+  expect(executeFn.mock.calls[0][0].contextValue).toBe(context);
+
+  await new Promise((resolve) => {
+    client.send(
+      stringifyMessage<MessageType.Subscribe>({
+        id: '2',
+        type: MessageType.Subscribe,
+        payload: {
+          query: `subscription { greetings }`,
+        },
+      }),
+    );
+    client.onmessage = ({ data }) => {
+      const message = parseMessage(data);
+      if (message.type === MessageType.Complete && message.id === '2') {
+        resolve();
+      }
+    };
+  });
+
+  expect(subscribeFn).toBeCalled();
+  expect(subscribeFn.mock.calls[0][0].contextValue).toBe(context);
+});