Feature request: add options to use location.port for hmr connection.

[lcjnil]

Clear and concise description of the problem

We use vite dev server locally and behind proxy, for example, we start vite at localhost:8080, we want to access it via http://localhost:8080 or we use local proxy (caddy, nginx, whistle...) to access via some domain(like http://local.dev.app).

But currently, vite's hmr options is not working for our scenario. Vite can only configure hmr's websocket port to one specific port, which means we can't let it connect in ws://localhost:8080 when access via http://localhost:8080 and connect in ws://local.dev.app via http://local.dev.app.

And we cannot find any way to edit it dynamicly.

The code is https://github.com/vitejs/vite/blob/v2.6.9/packages/vite/src/node/plugins/clientInjections.ts#L26-L34

Suggested solution

We can add an option to enforce hmr connection use location.port, like server.hmr.useLocationPort.

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[malobre]

I use a similar setup (caddy proxy) to try and make the development environment as similar to production as possible (w.r.t https, CORS, subdomains, etc).
This would be a very useful feature.

[malobre]

This seems to be a duplicate of #3093

[Niputi]

duplicate of #3093