test: verify middleware req.body/query/params/headers modifications reach handler

Author: yanxue-22

packages/express-wrapper/src/middleware.ts

@@ -202,7 +202,7 @@ export async function runMiddlewareChainIgnoringResults<
   Input,
   Chain extends MiddlewareChain,
 >(
-  input: Input,
+  _input: Input,
   chain: Chain,
   req: express.Request,
   res: express.Response,
@@ -216,11 +216,11 @@ export async function runMiddlewareChainIgnoringResults<
       }
     });
   }
-  return { 
-    ...(req as any).decoded, 
-    ...(req.body || {}), 
-    ...(req.query || {}), 
+  return {
+    ...(req as any).decoded,
+    ...(req.body || {}),
+    ...(req.query || {}),
     ...(req.params || {}),
-    ...(req.headers || {})
+    ...(req.headers || {}),
   };
 }

packages/express-wrapper/test/middleware.test.ts

@@ -40,38 +40,6 @@ test('should handle errors passed to next()', async () => {
   );
 });
 
-test('middleware that modifies req should pass changes through chain', async () => {
-  const testReq = { body: {}, headers: {} } as express.Request;
-  const testRes = {} as express.Response;
-
-  const modifyReqMiddleware: express.RequestHandler = (req, _res, next) => {
-    (req as any).userId = 123;
-    next();
-  };
-
-  const checkReqMiddleware: express.RequestHandler = (req, _res, next) => {
-    assert.equal(
-      (req as any).userId,
-      123,
-      'userId should still be on req in second middleware',
-    );
-    next();
-  };
-
-  await runMiddlewareChain(
-    { foo: 'test' },
-    [modifyReqMiddleware, noopMiddleware, checkReqMiddleware],
-    testReq,
-    testRes,
-  );
-
-  assert.equal(
-    (testReq as any).userId,
-    123,
-    'req should still have userId after chain',
-  );
-});
-
 test('should work with middleware that return values', async () => {
   const result = await runMiddlewareChain(
     { foo: 'test' },

packages/express-wrapper/test/server.test.ts

@@ -276,3 +276,66 @@ test('should return a 400 when request fails to decode', async () => {
 
   assert(response.body.error.startsWith('Invalid value undefined supplied to'));
 });
+
+test('middleware that modifies req.body should reach handler even without routeHandler()', async () => {
+  const PostWithData = httpRoute({
+    path: '/data',
+    method: 'POST',
+    request: httpRequest({
+      body: {
+        originalField: t.string,
+        addedByMiddleware: optional(t.string),
+      },
+    }),
+    response: {
+      200: t.type({
+        originalField: t.string,
+        addedByMiddleware: optional(t.string),
+      }),
+    },
+  });
+
+  const testApiSpec = apiSpec({
+    'test.route': {
+      post: PostWithData,
+    },
+  });
+
+  const modifyBodyMiddleware: express.RequestHandler = (req, _res, next) => {
+    req.body.addedByMiddleware = 'ADDED';
+    next();
+  };
+
+  const handler = async (params: {
+    originalField: string;
+    addedByMiddleware?: string;
+  }) => {
+    return {
+      type: 200,
+      payload: {
+        originalField: params.originalField,
+        addedByMiddleware: params.addedByMiddleware,
+      },
+    } as const;
+  };
+
+  const app = createServer(testApiSpec, (app: express.Application) => {
+    app.use(express.json());
+    return {
+      'test.route': {
+        post: { middleware: [modifyBodyMiddleware], handler },
+      },
+    };
+  });
+
+  const response = await supertest(app)
+    .post('/data')
+    .send({ originalField: 'test' })
+    .expect(200);
+
+  assert.equal(
+    response.body.addedByMiddleware,
+    'ADDED',
+    'addedByMiddleware should be present because req.body is part of req.decoded',
+  );
+});