How to setup pylsp with black formatter?

[MarkuBu]

Hi, I try to configure the Python LSP for Helix. The LSP itself is running. But I want to add the black formatter plugin, but it doesn't work automatically.

I created a venv and activated it. Then I installed pylsp with pip. If I open a file in Helix the LSP is working. I installed the black lsp plugin and I can run black manually. But I don't know how to run it automatically inside Helix, e.g. if I save a file, and reload the new version.

How can I set this up?

Edit: found the answer

https://github.com/helix-editor/helix/wiki/External-binary-formatter-configuration#black

[akhilman]

Black formatter can be integrated to pylsp itself. Here is my configuration (not tested, just ported from NeoVIM):

languages.toml

[language-server.pylsp.config.pylsp]
plugins.black.enabled = true
plugins.pylint.enabled = true
plugins.pyflakes.enabled = false
plugins.pyls_mypy.enabled = true
plugins.pyls_mypy.live_mode = false
plugins.isort.enabled = true
plugins.rope_autoimport.enabled = true

And requirements.txt to install everything needed:

black
isort
jedi
pyflakes
pylint
pyls-isort
python-lsp-black
python-lsp-server[rope,pylint]
rope

Update Dec 11 2023:
Tested it in a virtual environment. everything works fine. The ending of the language-server.pylsp.config.pylsp is required, without this extra .pylsp auto-import does not work.

[marktforsyth]

Thanks, this is super helpful! Except I got an error on the fifth package, pyling. Did you perhaps mean pylint? When I made that change, everything worked.

[akhilman]

Yep. It was typo.

[dc740]

Thanks! I was looking for this. I may add that setting the isort profile in the pyproject.toml file of your project does wonders to the imports and general consistency.

[tool.black]
line-length = 100

[tool.pylint.format]
max-line-length = 100


[tool.isort]
line_length = 100
profile = "black"

As a side note, if you don't want to deal with manually installing each pylsp module, you can pip install python-lsp-server[all] and it will bring the other dependencies too.

UPDATE:
pycodestyle will show an error regarding the line length if you modify it for these tools, so the formatting will change the line length but the warning will pop up anyway. You need to tell pycodestyle the max line length, but since the pypropject.toml support on that project is weird (*) it's better to set it in the .helix/languages.toml file in your project (or in ~/.config/helix/languages.toml)

❯ cat .helix/languages.toml
[language-server.pylsp.config]
pylsp.plugins.black.enabled = true
pylsp.plugins.pylint.enabled = true
pylsp.plugins.pyflakes.enabled = false
pylsp.plugins.pyls_mypy.enabled = false
pylsp.plugins.pyls_mypy.live_mode = false
pylsp.plugins.isort.enabled = true
pylsp.plugins.rope_autoimport.enabled = true
pylsp.plugins.pycodestyle.maxLineLength = 100
pylsp.plugins.flake8.maxLineLength = 100

(* AFAIK they didn't want to add it PyCQA/pycodestyle#813 )