Any advice on picking a Python language server for emacs? (programming.dev)

submitted 2 months ago by webbureaucrat@programming.dev to c/python@programming.dev

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Hi, folks!

I'd like to set up my emacs with lsp-mode and lsp-ui, but I am finding myself in some analysis paralysis. Ruling out the Palantir language server because it's deprecated and because it's Palantir, that still leaves me with five language server recommendations from lsp-mode.

Anybody have any opinions they'd like to share? Any really bad experiences I should avoid? How do I configure your favorite? (Feel free to assume I know very little about configuring emacs.)

If it makes a difference, I am a poetry user and a religious mypy --strict user.

Thanks in advance!

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[-] eager_eagle@lemmy.world 3 points 2 months ago* (last edited 2 months ago)

Ruff.

MS LSP is also deprecated in favor of Microsoft's pylance AFAIK. I've never used Jedi much, but it's one of the older ones and not very comprehensive to my knowledge. Ruff is relatively new but they already have >800 rules and increasing. Ruff is by far the fastest too.

No thoughts on py-lsp.

Ah, just be sure to enable most (or all) rules with ruff, as the default rule sets are pretty relaxed.

[-] Fred@programming.dev 2 points 2 months ago

That seems like a weird dichotomy between ruff and Jedi. One does linting & formatting, the other code completion, goto-definition, refactoring. With pylsp you can have both: it uses Jedi (in the default config), and has a plugin to call ruff for linting and formatting (according to the doc; I don't actually use ruff).

[-] wewbull@feddit.uk 2 points 2 months ago

Sounds like things are going very wrong in lsp land. The point of a language server is to support lots of types of tools through an abstracted server. Not to have one server per tool.

Otherwise, just use fly-checker. It can even get information from multiple tools at once.

[-] eager_eagle@lemmy.world 1 points 2 months ago

what do you mean by one server per tool?

[-] wewbull@feddit.uk 2 points 2 months ago

Op was listing different Lsp servers for things like jedi, pyright, etc. All of those things should really integrate with a single server.

[-] eager_eagle@lemmy.world 1 points 2 months ago

insert standards xkcd

[-] eager_eagle@lemmy.world 1 points 2 months ago* (last edited 2 months ago)

I forgot pyright: it might be a good choice, but since you like strict mode, see basedpyright instead. I don't know about integrating it with emacs though.

I'd pick between Ruff and (based)pyright - maybe both if that works in emacs.

[-] Fred@programming.dev 2 points 2 months ago

I'm using pylsp (python-language-server). My reason being a process of elimination. I also use mypy for type-checking, so even without considering the danger of allowing MS to entrench itself into my tooling, it didn't make much sense to use a tool built around pyright.

The ruff-lsp seems to only do the things that ruff is good at: linting, code formatting, auto-fix of certain issues, and I wanted more.

Since I saw that pylsp uses Jedi under the hood, and offered a mypy plugin, I felt that pylsp offer a superset of the features that the Jedi LSP has. In the end I'm happy with pylsp, and never tried Jedi LSP.

However: with the mypy plugin for pylsp, the memory usage kept growing to ridiculous amounts and getting killed, so I ended up disabling it. I had a look in their bug tracker Instead, I'm using flymake that triggers mypy on save, and that seems to work well. (I have a few changes on top of com4/flymake-mypy.el, because it leaves behind plenty of temporary files.)

That offers me:

jump to definition (using Jedi under the hood)
rename symbol (and then Jedi goes and rename uses of that symbol)
smart completion (eg. offers only variables in scope, or after a . only the instance members, etc.)
short documentation on hover
squiggly lines for errors found by flake8 or mypy
and a few more that I don't really notice

One thing I struggled with: where do you install the LSP? Using pipx for a user installation, or in a per-project venv? I did the latter, which works for me because I work on a small number of projects. That also means that mypy finds all the relevant third-party libraries in that venv. I wrote a bit of elisp that allow emacs to find the right mypy binary to check code.

[-] fossphi@lemm.ee 2 points 2 months ago* (last edited 2 months ago)

Another recommendation for pylsp. Ruff is good, but it doesn't provide lookups and completions. For now, think of it as just a linter/formatter to augment pylsp

[-] FizzyOrange@programming.dev 1 points 2 months ago

In VSCode the best answer by far is Pylance, which uses Pyright under the hood for type analysis.

Unfortunately while Pyright is open source, Pylance isn't (part of Microsoft's strategy to maintain control over VSCode), so you can't use it in Emacs.

Still, I would give the Pyright LSP server a try. I haven't used it but I would guess it will give you type error squiggles but maybe not code completion / go-to-definition.

Ruff is really a different thing - it is a linter like Pylint, so it only gives you some hints and fixits. You can maybe install it in addition to Pyright if you can be bothered.

Btw Pyright is far superior to Mypy - even with --strict. I would ditch Mypy asap.