Serve on Windows spawns many terminals

[grouma]

Root cause of issue outlined here: #110

I believe one solution is to update the persistent workers in package:build_modules to also start from the snapshot instead of the .bat files.

[grouma]

We'll need to update package:build_modules to always spawn with mode detachedWithStdio. We'll also need to work around dart-lang/sdk#35874

[natebosch]

Why do we need detachedWithStdio if we're running from a snapshot?

If we want to run from a snapshot, should we run in an isolate?

[grouma]

The daemon needs to continue to run when webdev is killed. detachedWithStdio provides this behavior. I don't think it's possible to do this with an isolate.

[natebosch]

The persistent workers in build_modules have the same lifespan as the daemon... Are those the workers under discussion?

[grouma]

Sorry, there are a couple things going on so let me be clear.

WebDev starts the daemon through package:build_daemon here:
https://github.com/dart-lang/build/blob/master/build_daemon/lib/client.dart#L75

Obviously this process needs to be long running and thus uses detachedWithStdio. Right now it works around pub spawning a new terminal by calling the snapshot directly:
https://github.com/dart-lang/webdev/blob/master/webdev/lib/src/serve/daemon_client.dart#L20

Ideally it would call pub.bat instead of the snapshot.

Now this daemon process spins up a bunch of worker processes through package:build_modules here: https://github.com/dart-lang/build/blob/master/build_modules/lib/src/workers.dart#L68

These don't necessarily have to be long running. Since they are spawned with the default process mode, they create new terminals. See why here: dart-lang/sdk#35809

We could change them to be isolates but that would be a breaking change to BazelWorkerDriver. These worker processes already properly shutdown if the daemon shuts down. I think it makes sense to leave them as processes and just update their mode.

[grouma]

This is mostly resolved. There is still a single flash of a terminal due to dart-lang/pub#2042

[jakemac53]

@grouma should we close this?

[grouma]

There is no work to be done on webdev. This issue will be fully resolved once dart-lang/pub#2042 is resolved.

[grouma]

Closing this since there isn't work to be done in webdev.