feat (web-server): allow injection of custom middleware.

Closes #1612

lib/web-server.js

@@ -63,9 +63,15 @@ var createWebServer = function (injector, emitter, fileList) {
     // TODO(vojta): remove, this is only here because of karma-dart
     // we need a better way of custom handlers
     .use(injector.invoke(createCustomHandler))
-    .use(function (request, response) {
-      common.serve404(response, request.url)
-    })
+
+
+  if(config.middleware) {
+    config.middleware(handler);
+  }
+
+  handler.use(function (request, response) {
+    common.serve404(response, request.url)
+  })
 
   var serverClass = http
   var serverArguments = [handler]

test/unit/web-server.spec.js

@@ -31,6 +31,7 @@ describe('web-server', () => {
   // this relies on the fact that none of these tests mutate fs
   var m = mocks.loadFile(__dirname + '/../../lib/web-server.js', _mocks, _globals)
 
+  var middlewareActivated = false;
   var customFileHandlers = server = emitter = null
 
   var servedFiles = (files) => {
@@ -41,9 +42,22 @@ describe('web-server', () => {
     beforeEach(() => {
       customFileHandlers = []
       emitter = new EventEmitter()
+      var config = {
+        basePath: '/base/path',
+        urlRoot: '/',
+        middleware: function(connect) {
+          connect.use(function (request, response, next) {
+            if(middlewareActivated) {
+              response.writeHead(222)
+              return response.end('middleware!')
+            }
+            next()
+          })
+        }
+      }
 
       var injector = new di.Injector([{
-        config: ['value', {basePath: '/base/path', urlRoot: '/'}],
+        config: ['value', config],
         customFileHandlers: ['value', customFileHandlers],
         emitter: ['value', emitter],
         fileList: ['value', {files: {served: [], included: []}}],
@@ -81,6 +95,25 @@ describe('web-server', () => {
         .expect(200, 'new-js-source')
     })
 
+    describe('middleware', function() {
+      beforeEach(() =>{
+        servedFiles(new Set([new File('/base/path/one.js')]))
+        middlewareActivated = true;
+      })
+
+      it('should use injected middleware', () => {
+        return request(server)
+          .get('/base/other.js')
+          .expect(222, 'middleware!')
+      })
+
+      it('should inject middleware behind served files', () => {
+        return request(server)
+          .get('/base/one.js')
+          .expect(200, 'js-source')
+      })
+    })
+
     it('should serve no files when they are not available yet', () => {
       return request(server)
         .get('/base/new.js')