Add promise support

lib/layer.js

@@ -47,6 +47,31 @@ function Layer(path, options, fn) {
   }
 }
 
+/**
+ * Handle any request for the layer.
+ *
+ * @api private
+ */
+
+Layer.prototype._handle_any = function _handle_any(/* ...args, next */) {
+  var self = this
+  var next = arguments[arguments.length - 1]
+  var handle = this.handle
+  var result
+  var hasNextBeenCalled = function () { return next._currentLayer === self }
+
+  try {
+    result = handle.apply(undefined, arguments)
+  } catch (err) {
+    return next(err)
+  }
+
+  if (result != null && typeof result.then === 'function') {
+    var onRejected = function (error) { if (!hasNextBeenCalled()) { next(error) } }
+    result.then(null, onRejected)
+  }
+}
+
 /**
  * Handle the error for the layer.
  *
@@ -58,18 +83,12 @@ function Layer(path, options, fn) {
  */
 
 Layer.prototype.handle_error = function handle_error(error, req, res, next) {
-  var fn = this.handle
-
-  if (fn.length !== 4) {
+  if (this.handle.length !== 4) {
     // not a standard error handler
     return next(error)
   }
 
-  try {
-    fn(error, req, res, next)
-  } catch (err) {
-    next(err)
-  }
+  this._handle_any(error, req, res, next)
 }
 
 /**
@@ -82,18 +101,12 @@ Layer.prototype.handle_error = function handle_error(error, req, res, next) {
  */
 
 Layer.prototype.handle_request = function handle(req, res, next) {
-  var fn = this.handle
-
-  if (fn.length > 3) {
+  if (this.handle.length > 3) {
     // not a standard request handler
     return next()
   }
 
-  try {
-    fn(req, res, next)
-  } catch (err) {
-    next(err)
-  }
+  this._handle_any(req, res, next)
 }
 
 /**

lib/route.js

@@ -127,6 +127,9 @@ Route.prototype.dispatch = function dispatch(req, res, done) {
       match = !layer.method || layer.method === method
     }
 
+    // set a reference to the current layer
+    next._currentLayer = layer
+
     // no match
     if (match !== true) {
       return done(err)

package.json

@@ -16,6 +16,7 @@
   },
   "devDependencies": {
     "after": "0.8.1",
+    "bluebird": "2.10.2",
     "finalhandler": "0.4.0",
     "istanbul": "0.3.17",
     "mocha": "2.2.5",

test/promise.js

@@ -0,0 +1,88 @@
+
+var Router = require('..')
+var utils = require('./support/utils')
+var Promise = require('bluebird')
+
+var assert = utils.assert
+var createServer = utils.createServer
+var request = utils.request
+
+describe('Promise', function () {
+  it('rejecting will trigger error handlers', function (done) {
+    var router = Router()
+    var server = createServer(router)
+
+    router.use(function (req, res) {
+      return new Promise(function (resolve, reject) {
+        reject(new Error('Happy error'))
+      })
+    })
+
+    request(server)
+    .get('/')
+    .expect(500, done)
+  })
+
+  it('will be ignored if next is called', function (done) {
+    var router = Router()
+    var server = createServer(router)
+    var count = 0
+
+    router.use(function (req, res, next) {
+      count++
+      return new Promise(function (resolve, reject) {
+        count++
+        next()
+        setTimeout(function () {
+          count++
+          resolve()
+        }, 5)
+      })
+    })
+
+    router.use(function (req, res) {
+      assert.equal(count, 2)
+      res.end('Awesome!')
+    })
+
+    request(server)
+    .get('/')
+    .expect(200, done)
+  })
+
+  it('can be used in error handlers', function (done) {
+    var router = Router()
+    var server = createServer(router)
+    var count = 0
+
+    router.use(function (req, res, next) {
+      count++
+      next(new Error('Happy error'))
+    })
+
+    router.use(function (error, req, res, next) {
+      count++
+      return new Promise(function (resolve, reject) {
+        count++
+        setTimeout(function () {
+          count++
+          next(error)
+          resolve()
+        }, 5)
+      })
+    })
+
+    router.use(function () {
+      done(new Error('This should never be reached'))
+    })
+
+    router.use(function (error, req, res, next) {
+      assert.equal(count, 4)
+      res.end('Awesome!')
+    })
+
+    request(server)
+    .get('/')
+    .expect(200, done)
+  })
+})