How does Python LSP integration work?

[cbarrete]

My understanding is that Python LSP integration is supposed to be built using the source-db subtargets (and accompanying BXL scripts in the prelude), but I cannot find any mentions of "source db" in language server docs.
I'm very unfamiliar with the Python ecosystem, could somebody give me some pointers for where to start looking?

My understanding is that in the Bazel world, this is achieved by making venvs that contain both third-party and local dependencies. Is it similar in the Buck2 world?

I've looked at the git log for prelude/python/sourcedb/ide.bxl, but it's not quite enough context I believe.

[connernilsen]

Hey @cbarrete, I have an understanding of how this works internally for the Pyre type checker, but let me see if I understand your question correctly. Are you looking to build the source-db and use it in some other language server? Which Python LSP integration do you mean?

The source-db is a mapping from files on disk to where files would end up in a par (so essentially how files get remapped in the resulting executable). It also makes sure any other generated files are 'ensured', so they exist on disk for you to utilize. Depending on what you're looking for here, one of the other sourcedb scripts might be more useful to you, or this may be doing something other than what you're expecting.

For Pyre, we use the resulting sourcedb to understand what file an import in a Python file actually points to, and to make sure something like a .pyi file generated from specific c(++) rules exist for us to use.