From 70971dcb53db88c1801ff837223142478142782a Mon Sep 17 00:00:00 2001
From: TJ Holowaychuk <tj@vision-media.ca>
Date: Thu, 19 Dec 2013 10:03:08 -0800
Subject: [PATCH] add GeneratorFunction assertion for app.use(). Closes #120

breaks old old shit but thats ok, super early in the game
---
 lib/application.js      |  4 +++-
 test/application.js     | 11 +++++++++++
 test/response/status.js | 20 +++++++++-----------
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/lib/application.js b/lib/application.js
index 8a8b35d..c59a089 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -10,6 +10,7 @@ var request = require('./request');
 var response = require('./response');
 var Cookies = require('cookies');
 var Keygrip = require('keygrip');
+var assert = require('assert');
 var Stream = require('stream');
 var http = require('http');
 var co = require('co');
@@ -71,12 +72,13 @@ app.listen = function(){
 /**
  * Use the given middleware `fn`.
  *
- * @param {Function} fn
+ * @param {GeneratorFunction} fn
  * @return {Application} self
  * @api public
  */
 
 app.use = function(fn){
+  assert('GeneratorFunction' == fn.constructor.name, 'app.use() requires a generator function');
   debug('use %s', fn.name || '-');
   this.middleware.push(fn);
   return this;
diff --git a/test/application.js b/test/application.js
index 64f7c8d..29c433b 100644
--- a/test/application.js
+++ b/test/application.js
@@ -58,6 +58,17 @@ describe('app.use(fn)', function(){
       done();
     });
   })
+
+  it('should error when a non-generator function is passed', function(done){
+    var app = koa();
+
+    try {
+      app.use(function(){});
+    } catch (err) {
+      err.message.should.equal('app.use() requires a generator function');
+      done();
+    }
+  })
 })
 
 describe('app.respond', function(){
diff --git a/test/response/status.js b/test/response/status.js
index b81f8e3..c01aa51 100644
--- a/test/response/status.js
+++ b/test/response/status.js
@@ -40,17 +40,15 @@ describe('res.status=', function(){
     it('should strip content related header fields', function(done){
       var app = koa();
 
-      app.use(function(next){
-        return function *(){
-          this.body = { foo: 'bar' };
-          this.set('Content-Type', 'application/json');
-          this.set('Content-Length', '15');
-          this.set('Transfer-Encoding', 'chunked');
-          this.status = status;
-          assert(null == this.response.header['content-type']);
-          assert(null == this.response.header['content-length']);
-          assert(null == this.response.header['transfer-encoding']);
-        }
+      app.use(function *(){
+        this.body = { foo: 'bar' };
+        this.set('Content-Type', 'application/json');
+        this.set('Content-Length', '15');
+        this.set('Transfer-Encoding', 'chunked');
+        this.status = status;
+        assert(null == this.response.header['content-type']);
+        assert(null == this.response.header['content-length']);
+        assert(null == this.response.header['transfer-encoding']);
       });
 
       request(app.listen())