build_runner build_runner serve --live-reload doesn't reload on changes

[jhenso]

Hello, according to build_runner documentation:

Some commands also have additional options:

serve
--hostname: The host to run the server on.
--live-reload: Enables automatic page reloading on rebuilds.

However if you run dart run build_runner serve --live-reload, the application is built and served, but live-reload doesn't work, with the following error when the browser tries to connect to the WebSocket:

Serving `web` on http://localhost:8080
ERROR - 2022-10-17 10:06:11.398101
Asynchronous error
NoSuchMethodError: Closure call with mismatched arguments: function 'BuildUpdatesWebSocketHandler.createHandlerByRootDir.closureForRootDir'
Receiver: Closure: (WebSocketChannel, String) => void
Tried calling: BuildUpdatesWebSocketHandler.createHandlerByRootDir.closureForRootDir(Instance of 'WebSocketChannel')
Found: BuildUpdatesWebSocketHandler.createHandlerByRootDir.closureForRootDir(WebSocketChannel, String) => void
dart:core                                                   _objectNoSuchMethod
package:shelf_web_socket/shelf_web_socket.dart 49:55        webSocketHandler.<fn>
package:shelf_web_socket/src/web_socket_handler.dart 81:20  WebSocketHandler.handle.<fn>

Repository with minimal reproduction: https://github.com/jhenso/dart-build-runner

• Dart SDK Version (dart --version)
  Dart SDK version: 2.18.2 (stable) (Tue Sep 27 13:24:11 2022 +0200) on "macos_x64"

• What package(s) from this repo you are using, and the version (i.e. build_runner 0.7.12)

• build_runner 2.3.0
• build_runner_core 7.2.4
• build_web_compilers 3.2.6

• Whether you are using Windows, MacOSX, or Linux (if applicable)
  MacOSX
• Whether you are using Chrome, Safari, Firefox, Edge (if applicable)
  Chrome

[jakemac53]

cc @grouma I think we maybe added a client ID to this so we could have multiple channels?

[grouma]

I'm not sure what client ID you are referring to. I'm pretty sure this has been broken since #1786. I'm not sure why closureForRootDir takes a String protocol parameter.

[jakemac53]

I am probably just misremembering, I hadn't actually looked into this at all I just thought you had added something for multiple apps on the page so we could know which one we were talking to

[jakemac53]

@jhenso if you want to take a look at fixing this we would accept a PR. Given it has been broken for a long time without any issues being filed, it probably isn't going to be high priority to fix.

[simolus3]

It looks like this is actually a bug in shelf_web_socket, this should be (Never, Never) to test for a binary function. Null is no longer a bottom type, so build_runner's callback of void Function(WebSocketChannel, String) is not a void Function(Null, Null).

https://github.com/dart-lang/shelf/blob/39d820d4e32fc99c65f562786097487d597dcee1/pkgs/shelf_web_socket/lib/shelf_web_socket.dart#L46

Why this surfaces in build_runner and not in shelf_web_socket tests is another question. Do these original tests not run with sound null safety? Maybe this got broken by migrating build_runner to sound null safety?