From 3560651bbc3a6a026014d9259a8bd4bfb79609df Mon Sep 17 00:00:00 2001
From: blaz <blaz@menems.net>
Date: Thu, 29 Oct 2015 18:25:46 +0100
Subject: [PATCH] Add usage of koa-convert for legacy middleware

closes #565
closes #538
---
 Readme.md               | 13 ++++++++-----
 lib/application.js      |  2 +-
 test/application/use.js |  2 +-
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/Readme.md b/Readme.md
index ccdd77e..773feb5 100644
--- a/Readme.md
+++ b/Readme.md
@@ -116,25 +116,28 @@ app.use(ctx => {
 app.listen(3000);
 ```
 
-## Example with old version, Koa < 2
+## Example with old signature
+
+If you want to use old signature or be compatible with old middleware, you must use [koa-convert](https://github.com/gyson/koa-convert) to convert legacy generator middleware to promise middleware.
 
 ```js
 const Koa = require('koa');
 const app = new Koa();
+const convert = require('koa-convert')
 
 // logger
 
-app.use(function *(next){
+app.use(convert(function *(next){
   const start = new Date;
   yield next;
   const ms = new Date - start;
   console.log(`${this.method} ${this.url} - ${ms}`);
-});
+}));
 
 // response
 
-app.use(function *(){
-  this.body = 'Hello World';
+app.use(ctx => {
+  ctx.body = 'Hello World';
 });
 
 app.listen(3000);
diff --git a/lib/application.js b/lib/application.js
index ed9e231..ee84090 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -92,7 +92,7 @@ module.exports = class Application extends Emitter {
   use(fn) {
     debug('use %s', fn._name || fn.name || '-');
     if (typeof fn !== 'function') throw new TypeError('middleware must be a function!');
-    if (isGeneratorFunction(fn)) throw new TypeError('Support for generators has been removed. Use Promises or wrap your generator with co.wrap');
+    if (isGeneratorFunction(fn)) throw new TypeError('Support for generators has been removed. See the documentation for examples of how to convert old middleware https://github.com/koajs/koa#example-with-old-signature');
     this.middleware.push(fn);
     return this;
   }
diff --git a/test/application/use.js b/test/application/use.js
index bdda573..b04c500 100644
--- a/test/application/use.js
+++ b/test/application/use.js
@@ -66,6 +66,6 @@ describe('app.use(fn)', function(){
   it('should throw error for generator', function(){
     const app = new Koa();
 
-    (() => app.use(function *(){})).should.throw('Support for generators has been removed. Use Promises or wrap your generator with co.wrap');
+    (() => app.use(function *(){})).should.throw(/.+/);
   });
 });