Devtools not usable when attached to application running in custom embedder

[planetmarshall]

Summary

When devtools is attached to a Flutter application running in a custom embedder, limited functionality is available.

Steps to reproduce

1. Launch the demo GLFW embedder. In the console, the VM URL will be output, for example The Dart VM service is listening on http://127.0.0.1:38217/ajHHm0ZNdFs=/
2. Following the documentation in Using-the-Dart-Development-Service-(DDS)-and-Flutter-DevTools-with-a-custom-Flutter-Engine-Embedding, run the dart development service as follows, passing the above URI:

$ dart development-service --serve-devtools --vm-service-uri=http://127.0.0.1:38217/ajHHm0ZNdFs=/
 {"state":"started","ddsUri":"http://127.0.0.1:38961/p_UkyRqO53E=/","devToolsUri":"http://127.0.0.1:38961/p_UkyRqO53E=/devtools/?uri=ws://127.0.0.1:38961/p_UkyRqO53E=/ws","dtd":{"uri":"ws://127.0.0.1:36099/vkodRgwXROU="}}

3. Open the devToolsUri in a browser

Expected result

(Image from same application run in the Linux Desktop embedder)

Devtools launches in a browser and is fully usable

Actual result

Devtools launches but displayed information is incorrect and most functionality is not available.

• Flutter Inspector and Debugger tabs are not present.

Flutter DevTools tab:

• Connected app type is incorrect. Reports Flutter native (profile build), is actually a debug build

Performance tab:

Non functional - just a spinning wheel (an error ParallelWaitError: Exception: No Flutter Views to query: {type: FlutterViewList, views: []} appears in the web developer console log`

See also

• Document how to configure DDS and DevTools for custom embedders flutter#139241
• DevTools fails to connect to Flutter applications not launched with flutter_tool #6848

[elliette]

Thanks for the report! I believe this is a duplicate of #6848

DevTools determines whether or not it is connected to a Flutter app based on whether or not flutter_tools has registered the Flutter version service extension. In this case, since you running the app without Flutter tools (here: https://github.com/flutter/flutter/blob/1ccdcc2da596cafe5f72def54f32ff0708d94ab1/engine/src/flutter/examples/glfw/run.sh#L42), the Flutter version service extension is never registered.

As a temporary workaround, I believe the custom embedder could register the Flutter version service extension, similarly to what flutter tools does, to notify DevTools that this is a Flutter app: https://github.com/flutter/flutter/blob/1ccdcc2da596cafe5f72def54f32ff0708d94ab1/packages/flutter_tools/lib/src/vmservice.dart#L222-L234