feat: send 204 response if null is returned from handler

src/app.ts

@@ -133,8 +133,11 @@ export function createAppEventHandler (stack: Stack, options: AppOptions) {
         return send(event, val, MIMES.html)
       } else if (isStream(val)) {
         return sendStream(event, val)
+      } else if (val === null) {
+        event.res.statusCode = 204
+        return send(event)
       } else if (type === 'object' || type === 'boolean' || type === 'number' /* IS_JSON */) {
-        if (val && (val as Buffer).buffer) {
+        if (type === 'object' && val.buffer) {
           return send(event, val)
         } else if (val instanceof Error) {
           throw createError(val)

src/utils/response.ts

@@ -4,7 +4,7 @@ import { MIMES } from './consts'
 
 const defer = typeof setImmediate !== 'undefined' ? setImmediate : (fn: Function) => fn()
 
-export function send (event: CompatibilityEvent, data: any, type?: string): Promise<void> {
+export function send (event: CompatibilityEvent, data?: any, type?: string): Promise<void> {
   if (type) {
     defaultContentType(event, type)
   }

test/app.test.ts

@@ -19,6 +19,23 @@ describe('app', () => {
     expect(res.body).toEqual({ url: '/' })
   })
 
+  it('can return a 204 response', async () => {
+    app.use('/api', () => null)
+    const res = await request.get('/api')
+
+    expect(res.statusCode).toBe(204)
+    expect(res.text).toEqual('')
+    expect(res.ok).toBeTruthy()
+  })
+
+  it('can return primitive values', async () => {
+    app.use('/number', () => 42)
+    expect(await request.get('/number').then(r => r.body)).toEqual(42)
+
+    app.use('/bool', () => true)
+    expect(await request.get('/bool').then(r => r.body)).toEqual(true)
+  })
+
   it('can return Buffer directly', async () => {
     app.use(() => Buffer.from('<h1>Hello world!</h1>', 'utf8'))
     const res = await request.get('/')