pub serve hangs forever after code change on 0.13.0

[ewot]

Pub serve (both from cli and from editor) works on first access. But after changing a dart file and reloading the app the browser hangs forever on loading the .dart or .dart.js file depending on if using Dartium or Chrome.

To reproduce:

1. run the hello_world.dart example from Dart editor
2. wait until initialized and running in Dartium
3. change some whitespace in hello_world.dart
4. reload i dartium -> hangs forever on request GET hello_world.dart

This behaviour started after upgrading from 0.12 and adding the angular transformer to pubspec.yaml.

I'm running on Ubuntu 14.04 64bit and Dart SDK version 1.6.0-dev.4.0.

[taisph]

I'm seeing the same behavior on Ubuntu 14.04 64bit and Dart SDK version 1.5.3.

[ewot]

One workaround for me was to turn off the angular transformer and set DI to use dynamic type factories:

  Module.DEFAULT_REFLECTOR = new DynamicTypeFactories();
  applicationFactory()
      .addModule(new MainModule())
      .run();

I guess this generates huge output but at least the turn-around time is fast while developing. Hopefully there is a way to have the transformers off while running from editor and turn them on while running from cli, but I don't know how.

[taisph]

I can confirm setting Module.DEFAULT_REFLECTOR = new DynamicTypeFactories(); stops pub serve from hanging on reload and re-runs (without explicitly stopping pub serve first). I didn't remove the angular transformer though.

[vicb]

Things you can try:

• run a pub upgrade (or upgarde via the editor) and report if this changes anything,
• run pub serve --verbose from the command line rather than from the IDE (to see if the issue is related to angular or the editor).

[taisph]

@vicb I just tried that and it hangs with no apparent error. The trigger seems to be changing and saving a dart-file. I assume it should say MSG : Build completed successfully after the save as it does when editing and saving an html-file but it never does.

Reloading the browser page shows a few requests and then just sits there waiting for "main.dart".

pub serve output hitting reload in browser window:

FINE: Instance of 'BarbackServer' GET /packages/browser/dart.js
    | Loading browser|lib/dart.js
FINE: Instance of 'BarbackServer' GET /packages/browser/dart.js
    | getAssetById(browser|lib/dart.js) returned
FINE: Instance of 'BarbackServer' GET /index.html
    | Loading angular_dart_attach_test|web/index.html
FINE: Instance of 'BarbackServer' GET /index.html
    | getAssetById(angular_dart_attach_test|web/index.html) returned
MSG : [web] GET /packages/browser/dart.js → browser|lib/dart.js
MSG : [web] GET /index.html → angular_dart_attach_test|web/index.html
FINE: Instance of 'BarbackServer' GET /main.dart
    | Loading angular_dart_attach_test|web/main.dart
FINE: Instance of 'BarbackServer' GET /packages/browser/dart.js
    | Loading browser|lib/dart.js
FINE: Instance of 'BarbackServer' GET /packages/browser/dart.js
    | getAssetById(browser|lib/dart.js) returned
MSG : [web] GET /packages/browser/dart.js → browser|lib/dart.js

[vicb]

And if you terminate pub serve (ctrl+c) and execute it again ?

[taisph]

Browser says GET http://localhost:8080/main.dart net::ERR_CONNECTION_REFUSED. When I start pub again I can reload the browser properly.

I also noticed that MSG : [web] GET /main.dart → angular_dart_attach_test|web/main.dart never shows when it gets stuck.

[vicb]

I can reproduce the behavior (save + reload = hang). But when I terminate pub serve and relaunch it, it works. This is not an angular issue but a pub issue. Please create a ticket on dartbug.com

[taisph]

I cannot reproduce this when I downgrade angular to 0.12.0. Could you be more specific as to why this is a pub problem because I'm sure they'll throw it right back here given this information.

[vicb]

It is not an angular issue because:

• get a clean 0.13 & execute pub upgrade in the example folder
• execute pub serve & visit localhost:8080/hello_wold.html -> ok
• terminate pub
• update hello_world.dart
• execute pub serve & visit localhost:8080/hello_wold.html -> ok

Then there is not issue with angular.
However if you do not terminate pub before modifying the dart file, it fails.

[ewot]

It might still be a problem with the angular transformer. Removing it from pubspec fixes the problem.

However, I don't know if it is a general problem with transformers in pub or if it is the angular transformer specifically that triggers the issue.

[taisph]

I completely agree that that would point towards pub. I'm just focusing on the changes in Angular's transformer since disabling this seems to "fix" the problem and changes were made here between 0.12.0 and 0.13.0 - while pub itself didn't change. I just know a bug report towards pub would be rejected if I don't provide a near smoking gun. My last bug report against pub throwing an out-of-memory exception while upgrading was rejected "as designed". 😄

Poking around in the angular transformer it would seem like the InjectorGenerator change in lib/transformer.dart is correlated with the deadlock. I'm not experienced enough to completely understand the implementation but removing it seems to prevent the deadlock from happening - I can keep curl-getting the main.dart and I see "build completed successfully" messages when I change dart-files. I'll poke around some more before bothering the Dart team.

[vicb]

@taisph Maybe you can start by creating this dartbug with your findings and say that you're investigating. They can put the ticket on hold waiting for info if necessary.

[taisph]

I've used for too much time on this already. Reported the bug at dartbug.com.

https://code.google.com/p/dart/issues/detail?id=20312