python-language-server

How about the fact that some extensions like Remote Development [1] and LiveShare [2] work only on proprietary builds of vscode, and not on code-oss or vscodium? I get it that those are proprietary extensions, but they still show up in the extension marketplace for OSS builds. And I don't see a technical reason why they wont run on OSS builds, other than that the extension builders want it that way. And these extensions are important enough that you will end up downloading the proprietary build while you are too busy solving something with your team mates. This is a very subtle way to push even privacy-aware developers to use the proprietary build with built-in telemetry. And how about the fact that the de-facto reference implementation of LSP client (most language servers are developed against vscode) uses many undocumented and non-stand

Well there is Pyright by MS (that's what Pylance is based on) and python-language-server by MS - that one has been superseded by Pyright and is deprecated in Code. https://github.com/microsoft/pyright https://github.com/Microsoft/python-language-server The only(?) one not by MS is Jedi: https://github.com/pappasam/jedi-language-server

This title is inaccurate. The language server _is_ open source, and is available here: https://github.com/microsoft/python-language-server. This is the default one VSCode ships with. This issue is filed on Pylance, a new (released June 2020) language server that's currently still in beta (announcement: https://devblogs.microsoft.com/python/announcing-pylance-fas...). Also, like the contributor notes, a lot of the "secret sauce" in Pylance is part of the open source Pyright typechecker: https://github.com/microsoft/pyright.