`yarn start` allocates port 8000 all the time in addition to 4242 (or custom port)

[canova]

I noticed this while building another project that uses localhost:8000. It looks like we are exposing two localhost ports in for the development server.

One is coming from buildContext.serve here:

profiler/scripts/lib/dev-server.mjs

Line 64 in 2eba5df

const { hosts, port: esbuildServerPort } = await buildContext.serve({

And another one is that we actually use with 4242 port:

profiler/scripts/lib/dev-server.mjs

Lines 113 to 118 in 2eba5df

	server.listen(port, host, () => {
	if (onServerStart) {
	onServerStart(`http://${host}:${port}`);
	}
	resolve();
	});

In the first one, esbuild always allocates localhost:8000, which is easy to block other projects since that port is used pretty frequently.

It looks like we did this 2 step to implement the middleware approach (the second one does some header checks and adds headers to the response. It's not possible to do it with pure esbuild). I don't know how much it's necessary, but probably it was there in the previous webpack implementation.

[canova]

If we can't remove one of these servers, there might be a workaround. It looks like when I pass port: 0 to buildContext.serve it starts automatically picking a random ephemeral port instead, which might be better for us. I get ports like 52563 which I'm pretty sure is not going to be used by other projects.