Hot Restart should be notified to program code so it can dispose of resources.

[ditman]

I have a plugin/app that attaches a listener to the window.navigator.connection.onChange Stream.

However, when the app/plugin hot restarts, I don't have any opportunity of canceling my old listener before attaching again.

Since connection.onChange is a DOM global, I end up with callbacks firing multiple times (+1 after each hot reload).

Is there any way I can detect a Hot Restart from app/plugin code before it happens, so I can dispose of the resources I've taken?

See also: flutter/flutter#10437

(I have worked around this issue by writing directly to the onchange property of the underlying DOM object, but that is not "polite")

• SDK Version: 2.9.0-21.0.dev.flutter-06cb010247 (be) (Tue Jul 7 08:14:51 2020 +0000) on "linux_x64"
• OS: Linux (doesn't matter)
• Browser: Chrome (doesn't matter)

[jonahwilliams]

Running any/arbitrary user code on hot reload/restart has the risk of stalling or creating deadlocks in the core development experience. That is, If dependencies can hook into hot reload/restart they can break it too.

Are there less intrusive options here? If the problem is resource cleanup, can we try a more targeted solution?

[ditman]

This problem is caused, probably in part by the architecture of the app that causes this.

What does/doesn't survive when hot restart happens? Maybe there's a better lifecycle hook than initState to attach that listener... (Whatever is "symmetrical" to dispose, I guess?)

[ditman]

This can be solved by using Streams correctly (using transforms) instead of needing anything else from the outside world. Closing.

[ditman]

I take the above back, this is still happening. I tried to use reassemble from flutter, but that doesn't seem to be called in my app :/

[ditman]

/cc @ferhatb

[maks]

Sadly this problem is still an issue now, is not just for Dart on Web, is affecting more and more projects (see number of incoming issue links to the downstream bug on Flutter: flutter/flutter#10437) and is an issue for the growing use of FFI.

In my case, I'm using a library via FFI in a Flutter plugin that needs to be able to clean up resources, which is impossible with the current hot-restart behaviour, which leads to a much degraded developer UX of making hot-restart useless as hot-restart removes Dart side ref to the instance of the native libraries resources and it's not possible to re-initialise the native lib in that state, so the only thing I can do is hot-reload or full app stop and restart :-(

[pcrady]

Im running into this problem with websockets on web. See issue 93793 in flutter.