mojo: fail gracefully if ServiceRegistry can't find ServiceConnector

mojo/public/cpp/application/lib/service_registry.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/public/cpp/application/lib/service_registry.h"
 
 #include "mojo/public/cpp/application/application.h"
 #include "mojo/public/cpp/application/lib/service_connector.h"
 
 namespace mojo {
@@ skipping 40 matching lines @@
 void ServiceRegistry::BindRemoteServiceProvider(
     ScopedMessagePipeHandle service_provider_handle) {
   remote_service_provider_.Bind(service_provider_handle.Pass());
   remote_service_provider_.set_client(this);
 }
 
 void ServiceRegistry::ConnectToService(const mojo::String& service_url,
                                        const mojo::String& service_name,
                                        ScopedMessagePipeHandle client_handle,
                                        const mojo::String& requestor_url) {
-  if (!application_->AllowIncomingConnection(service_name, requestor_url)) {
+  if (!application_->AllowIncomingConnection(service_name, requestor_url) ||
+      name_to_service_connector_.find(service_name) ==

[viettrungluu, 2014/06/18 14:52:06]

I wonder if we shouldn't reverse the order of the checks, i.e., not call
application_->AllowIncomingConnection() on nonexistent service names.

(Just a thought. I'll defer to Dave's opinion on this.)

[tim (not reviewing), 2014/06/18 20:18:20]

I like that better than what I had. It seems more in line with the expectation
of AllowIncomingConnection that it only makes decisions for realistic
connections. Also, the way the test was structured was to increment a
num_connected_ bool as a side effect of an overridden AllowIncomingConnection,
which was weird in this case where the ++ happened but the connection didn't.
Now I can add an additional assertion to the unit test.  Done.

+          name_to_service_connector_.end()) {
     client_handle.reset();
     return;
   }
 
   internal::ServiceConnectorBase* service_connector =
       name_to_service_connector_[service_name];
   assert(service_connector);
   // requestor_url is ignored because the service_connector stores the url
   // of the requestor safely.
   return service_connector->ConnectToService(
       service_url, service_name, client_handle.Pass());
 }
 
 }  // namespace internal
 }  // namespace mojo