Allow custom domains in Vite's allowedHosts

[ryanclark]

#51356 introduces the change of setting allowedHost to whatever the domain of the proxy target is, if it isn't localhost. That doesn't really work for my setup, and possibly others, as I use a different domain than localhost and the proxy target. This allows the option of setting a VITE_HOST environment variable (I followed the same convention in TAG), so we're not allowing all hosts.

[ravicious]

Could be something like this to allow target and VITE_HOST at the same time because why not.

function resolveAllowedHost(target: string) {
  const allowedHosts = [];
  if (process.env.VITE_HOST) {
    allowedHosts.push(process.env.VITE_HOST);
  }

  if (target !== DEFAULT_PROXY_TARGET) {
    const { hostname } = new URL(`http://${target}`);

    allowedHosts.push(hostname);
  }

  return allowedHosts;
}

I guess it all comes down to which domains you have in the cert that Vite uses? But I noticed that the docs say "When using HTTPS, this check is skipped" and that is true, but the thing that falls apart without allowedHosts is websockets (and thus HMR).

[ryanclark]

Yeah I think if your cert accepts localhost it'll still work without setting allowedHosts - but first Vite will try the hostname you're using, so there will be one error in the console always, but HMR would still work

I think your suggestion is good, I'll add it