Is it possible to restart the language server in place and hand the connection over to a subprocess?

[dcermak]

I have a rather peculiar use-case for my language server: depending on the contents of the file that I am currently editing, I would like to restart the language server in a container and preferably seamlessly hand over the connection to the container process.

Background: this is about the rpm-spec-language server that unfortunately greatly depends on the system rpm. Simulating a different distribution really works best from within a container.

[tombh]

That's an interesting usecase. My first reaction is to put a light custom proxy in front of the LSP server. It could intercept the file open messages and depending on the contents, redirect to a different server. There may be a fair bit of maintenance, for example you might need to cache the startup message from the editor, so it can also be sent to any other LSP servers that the proxy sets up.