Need a way to specify --local-engine for locally built engine

[littlesome]

I'm using a locally built engine, all flutter commands should pass --local-engine argument or we will got an error : "You must specify --local-engine if you are using a locally built engine."

Maybe globalFlutterArgs is a good place to do this? src/extension/utils/processes.ts

[littlesome]

Found some flutter tools code convert environment variable LOCAL_ENGINE, FLUTTER_ENGINE into
--local-engine, --local-engine-src-path in flutter_tools
Should we do the same in setupToolEnv?

[DanTup]

I think you should be able to do this by just specifying the args in your launch.json:

{
	"name": "Flutter",
	"request": "launch",
	"type": "dart",
	"args": ["--local-engine", "foo"]
}

I don't have a locally built engine to test this, but if I supply only "--local-engine" it complains about not having the next argument.

Another option if those env settings work, is you could set dart.env in your VS Code User Settings (this would apply to all projects instead of just the one you modified launch.json), like:

"dart.env": {
  "LOCAL_ENGINE": "foo"
}

Do either of these do what you need?

[littlesome]

Hi, I think the args in launch.json is not passed to some spawn calls, such as:

• FlutterDaemon
• runFlutterInFolder in sdk.ts

The second option only works for some flutter tools which convert env LOCAL_ENGINE to --local-engine and pass it to flutter.
All flutter commands need --local-engine cmd line argument such as :

flutter doctor --local-engine=host_debug_unopt

---

And you can test with a simulated locally built engine:
(I am on Windows, and not sure if the steps below works for you)

• add a global env var FLUTTER_ENGINE=/some/path/
• create an empty dir named out/host_debug_unopt in /some/path/
• copy gen_snapshot from dart-sdk/bin/utils to /some/path/out/host_debug_unopt
• run flutter doctor and see if you got an error You must specify --local-engine if you are using a locally built engine.
• run flutter doctor --local-engine=host_debug_unopt

[DanTup]

Ah, I didn't realise it would affect things like the daemon. I don't think globalFlutterArgs is the best place for this, as that would make it completely global (eg. you can't override it per-workspace). I think it would be better handled similar to pubAdditionalArgs but because we can't read config in the debug adapter (at least, we can't when we move it back out of process) we'll need to pass it in.

I haven't tested it yet, but I think something like this may do?

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