Handle OPTIONS requests to spec (#48)

* add successful response for OPTIONS requests without calling inner callback

README.md

@@ -60,3 +60,7 @@ default: `86400`
 ##### `origin`
 
 default: `*`
+
+##### `runHandlerOnOptionsRequest`
+
+default: `false`

src/index.js

@@ -25,7 +25,8 @@ const cors = (options = {}) => handler => (req, res, ...restArgs) => {
     allowMethods = DEFAULT_ALLOW_METHODS,
     allowHeaders = DEFAULT_ALLOW_HEADERS,
     allowCredentials = true,
-    exposeHeaders = []
+    exposeHeaders = [],
+    runHandlerOnOptionsRequest = false
   } = options
 
   res.setHeader('Access-Control-Allow-Origin', origin)
@@ -43,7 +44,11 @@ const cors = (options = {}) => handler => (req, res, ...restArgs) => {
     res.setHeader('Access-Control-Max-Age', String(maxAge))
   }
 
-  return handler(req, res, ...restArgs)
+  if (preFlight && !runHandlerOnOptionsRequest) {
+    res.end()
+  } else {
+    return handler(req, res, ...restArgs)
+  }
 }
 
 module.exports = cors

src/test.js

@@ -228,18 +228,39 @@ test('allows remove allow credentials header', async t => {
   }
 })
 
-test('responds to OPTIONS requests', async t => {
+test('responds to OPTIONS requests without running handler', async t => {
   const cors = microCors()
-  const router = micro(cors(() => ({})))
+  let isHandlerCalled = false
+  const router = micro(cors((req, res) => {
+    isHandlerCalled = true
+    res.end()
+  }))
   const url = await listen(router)
-  const method = 'OPTIONS'
 
   const response = await request({
     url,
-    method,
+    method: 'OPTIONS',
+    ...testRequestOptions
+  })
+
+  t.is(response.statusCode, 200)
+  t.false(isHandlerCalled)
+})
+
+test('allows to run handler on OPTIONS request', async t => {
+  const cors = microCors({ runHandlerOnOptionsRequest: true })
+  let isHandlerCalled = false
+  const router = micro(cors((req, res) => {
+    isHandlerCalled = true
+    res.end()
+  }))
+  const url = await listen(router)
+
+  await request({
+    url,
+    method: 'OPTIONS',
     ...testRequestOptions
   })
 
-  t.deepEqual(200, response.statusCode)
-  t.deepEqual({}, response.body)
+  t.true(isHandlerCalled)
 })