fix(handler): context option can return a response

Author: enisdenjo

src/__tests__/handler.ts

@@ -1 +1,15 @@
-it.todo('should behave as advertised');
+import fetch from 'node-fetch';
+import { startTServer } from './utils/tserver';
+
+it('should use the response returned from context', async () => {
+  const server = startTServer({
+    context: () => {
+      return [null, { status: 418 }];
+    },
+  });
+
+  const url = new URL(server.url);
+  url.searchParams.set('query', '{ __typename }');
+  const res = await fetch(url.toString());
+  expect(res.status).toBe(418);
+});

src/handler.ts

@@ -453,8 +453,10 @@ export function createHandler<RawRequest = unknown>(
     }
 
     if (!('contextValue' in args)) {
-      args.contextValue =
+      const maybeResOrContext =
         typeof context === 'function' ? await context(req, args) : context;
+      if (isResponse(maybeResOrContext)) return maybeResOrContext;
+      args.contextValue = maybeResOrContext;
     }
 
     const validationErrs = validate(args.schema, args.document);