Using "args" in launch.json for an attach request reports an error

[cycloss]

Describe the bug

When trying to attach the debugger to a flutter app I get the error message:

There are multiple observatory ports available.
Rerun this command with one of the following passed in as the appId:

  flutter attach --app-id com.example.myApp
  flutter attach --app-id com.example.myApp (2)

However, there is no configuration option available for type dart in the launch.json for me to be able to specify app-id

My launch.json looks like this:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "debug app",
            "request": "attach",
            "type": "dart",
            "deviceId": "51ABDF9C-C54D-4811-BBDA-E733639AEC51",
        },
    ]
}

To Reproduce
Steps to reproduce the behavior:

1. Run an app in the terminal with flutter run
2. Run the debug app launch config specified above.

I've also tried not launching with flutter run by just tapping on the app in the emulator and then trying to attach but the same problem occurs.

Expected behavior

I expected to be able to attach to the running process.

Versions (please complete the following information):

• VS Code version: 1.57.1
• Dart extension version: 3.23.1
• Dart/Flutter SDK version: Flutter 2.2.1, Dart 2.13.1

[DanTup]

There's an open issue about improving this at #2722, although it will require some Flutter tooling changes (since the current message is just text that VS Code can't understand, nor does it know where to get those IDs from).

As a short-term workaround, you should be able to add to the args field in launch.json (["--app-id", "foo"]) though (if that doesn't work for you, let me know and we can re-open this to fix that). Thanks!

[cycloss]

@DanTup thanks for your response. Adding to the args field worked a treat. I initially thought of doing that, but the linter actually reports it as a problem if you add the args field when type is dart so I just assumed it wouldn't work.

The problem message is just: Property args is not allowed, even though it does actually work. Maybe a simple fix is just to allow the args field for the dart type?

[DanTup]

Thanks for confirming!

It definitely shouldn't be an error to add args.. I'll re-purpose this to take a look at that. Thanks!

[cycloss]

No problem. It's also worth mentioning that it's only reported as an error when the request is attach. It doesn't report an error when request is launch.

[DanTup]

Thanks - I suspected that might be the case as I was updating the title - if I remember correctly they have their own definitions. There's probably not been much reason to use args in attach before this, so may have been left off intentionally, but this seems like good reason to change it - we shouldn't report errors on settings that actually change behaviour.

Thanks!

[cycloss]

It's a fairly niche use case, but it is useful to be able to attach the debugger to a running app instead of having to wait a while for a restart when issuing a launch debug request. Thanks for your help.

[ksilz]

I had the same thing happening when debugging a Flutter app on iOS in IntelliJ. Adding --app-id com.yourhomeingoodhands.mobile.yhigh in the "Additional attach args" field of the "Run/Debug Configuration" of my Flutter app fixed it. That was suggested by somebody in the forum.