Prevent project shutdown on watch mode

[elyse0]

Hi, I've just discovered this package and I was surprised on how fast it was 🚀

Unfortunately I tried using it on watch mode, but the program kept ending on any file change (apparently someone else has already noticed the same issue #45 )

So... this is my shot into fixing it 🐞

Issue

In order to react to changes in our files, the watcher triggers a change event, that in turn triggers a project reload.

This project reload forces a supervisor restart, that in the code is implemented by killing the current process and creating a new one.

wds/src/Supervisor.ts

Lines 32 to 46 in f89b208

	restart() {
	if (this.process) {
	this.process.kill("SIGKILL");
	}
	this.process = spawn("node", this.argv, {
	cwd: process.cwd(),
	env: {
	...process.env,
	WDS_SOCKET_PATH: this.socketPath,
	WDS_EXTENSIONS: this.project.config.extensions.join(","),
	},
	stdio: [null, "inherit", "inherit", "ipc"],
	});

This process exit is caught in the supervisor exit event, but it's only prevented for the supervise mode case.

wds/src/index.ts

Lines 172 to 177 in f89b208

	project.supervisor.process.on("exit", (code) => {
	log.debug(`child process exited with code ${code}, ${options.supervise ? "not exiting because supervise mode" : "exiting..."}`);
	if (!options.supervise) {
	project.shutdown(code ?? 1);
	}
	});

Possible solution

My proposed solution is to add the missing reload on changes mode case, preventing to kill our 'project' on any file change.

Images

Running original file (watch mode is enabled by default)

Modifying and saving changes to file

Previously the program would just end, like in the logs of #45

[airhorns]

Ah, thanks for the PR! I think I've always just run with wds --watch --supervise to turn on both bits of behaviour! I agree though that it isn't very useful to turn on --watch without also turning on the supervise behaviour -- you told wds you wanted it to watch and that you're gonna make changes, seems silly it would just quit! What do you think about making the --watch flag imply the --supervise flag, documenting it like that and fixing the issue at a higher level when doing argparsing? Also curious what @gmalette thinks

[gmalette]

I've so far considered --watch to be fs-related, and --supervise to be essentially keep-alive, but that's perhaps the wrong way to think about it.

Given the role of wds, I can't think of a reason you'd want --supervise without --watch. Why keep the process alive, but not reload it with the changed code, except if it exited by itself and/or crashed?

I have used --watch without supervise to let the process die, when booting the process caused a significant amount of logs, making it hard to find the breakage.

Unless there's compelling arguments to keep --supervise, I think I'd be in favour of:

1. Getting rid of --supervise
2. --watch by default also keeps the project alive if the child process exits
3. Add a flag to --watch that allows the process to die

Given that my usage of --watch without --supervise may be a special case, I'd also be open to deferring (3).

[elyse0]

Okay, I've removed supervise mode

3. Add a flag to --watch that allows the process to die

I think--no-watch already does this, is that what you meant?

[airhorns]

LGTM after one comment! Thanks!

[gmalette]

I think--no-watch already does this, is that what you meant?

There's a subtle difference for long-running processes that don't automatically end. With only --watch changing its files will cause it to be reloaded. However, if it crashes (or exits normally for that matter), previously to this PR it would not have been restarted.

[gmalette]

@airhorns can you publish a new version pls?

[elyse0]

There's a subtle difference for long-running processes that don't automatically end. With only --watch changing its files will cause it to be reloaded. However, if it crashes (or exits normally for that matter), previously to this PR it would not have been restarted.

Got it. I also noticed the tests keep running infinitely, it's probably because, as you say, now the process doesn't end

https://github.com/gadget-inc/wds/runs/7234432137