How to format files on save using black with neovim and coc

Question

I'm trying to have python files format on save using black and neovim, with coc.

Coc config

I have the following coc config:

{
  "coc.preferences.useQuickfixForLocations": true,
  "coc.preferences.snippets.enable": true,

  // python config
  "python.venvFolders": [".virtualenvs"],
  "python.venvPath" : "~/",
  "python.linting.enabled": true,
  "python.linting.pylintEnabled": true,
  "python.jediEnabled": false,
  "python.formatting.provider": "black",
  "python.formatting.blackPath": "~/.virtualenvs/neovim/bin/black",
  "coc.preferences.formatOnSaveFiletypes": ["python"]
}

Venv packages

Within the venv above I have the following black version:

-> % which python
/Users/x/.virtualenvs/neovim/bin/python

(neovim) x@y [14:31:38] [~/.virtualenvs]
-> % pip list | grep black
black           19.10b0

Other packages in this env are:

-> % pip list
Package         Version
--------------- ---------
appdirs         1.4.4
attrs           19.3.0
black           19.10b0
click           7.1.2
greenlet        0.4.16
isort           5.1.4
jedi            0.17.2
msgpack         1.0.0
neovim          0.3.1
numpy           1.19.1
pandas          1.0.5
parso           0.7.1
pathspec        0.8.0
pip             20.1.1
pynvim          0.4.1
python-dateutil 2.8.1
pytz            2020.1
regex           2020.7.14
setuptools      41.2.0
six             1.15.0
toml            0.10.1
typed-ast       1.4.1

Behaviour / errors

I see no errors, but I see no results. For example I would expect the following to work given that setup is functioning:

# from
print('hi')
# to (having saved file)
print("hi")

I don't get this though, nothing happens.

Something unusual that does happen is that my buffer for a python file is constantly in need of saving. By which I mean - I constantly have No write since last change warning when trying to do :q, which makes me think there's something funny going on, but I don't know where.

Edit

Here is the output of :checkhealth

Edit 2

Black seems to be working, for me, these are settings that I currently have.

coc-settings.json

   "python.formatting.provider": "black",
   "python.formatting.blackPath": "~/.virtualenvs/neovim/bin/black",
   "coc.preferences.formatOnSaveFiletypes": ["python"]

I also have nothing of the psf/black plugin anymore, that was (i think) causing some issues.

Answer 1

This is a coc.nvim setup procedure that works for Neovim, which aims to:

• Use coc-pyright as language server.

• Provide static type checking from a Python virtualenv (e.g. I have created a venv called coc with pyenv, which resides in ~/.pyenv/versions, I'll use this as an example).

• Format with black manually and automatically on save.

So here is my setup procedure:

1. Configure venv in coc-settings.json:

   {
     "python.venvPath": "/Users/gbai/.pyenv/versions"
   }
   

   Here an absolute path is necessary for now, see this issue comment.

   Update: You could use ${env:HOME} (no space after :!) to replace ~:

   {
     "python.venvPath": "${env:HOME}/.pyenv/versions"
   }
   

2. Choose a Python language server:

   Per coc.nvim's official doc section, I installed coc-pyright as language server by

   :CocInstall coc-pyright
   

   It has its own config file pyrightconfig.json per project, and should be placed at project root. I simply put this line in pyrightconfig.json:

   {
     "venv": "coc"
   }
   

   Of course for different project, the venv differs.

3. Configure black

   Install black in the venv (coc in my config), and add these to coc-settings.json:

   {
     "python.formatting.provider": "black",
     "python.formatting.blackPath": "~/.pyenv/versions/coc/bin/black"
   }
   

   Interestingly, I can use relative path ~ here without problem.

4. Formatting

   As per this issue comment:

   • Use "coc.preferences.formatOnType": true to enable format on type feature.

   • Use "coc.preferences.formatOnSaveFiletypes": ["python"] to include filetypes you want format on save.

   • Use :call CocAction('format') to format currrent document.

   • Use

     xmap <leader>f  <Plug>(coc-format-selected)
     nmap <leader>f  <Plug>(coc-format-selected)
     

     to format selected range.

   To inspect if formatting went well, as per this issue comment:

   coc-pyright v1.1.97 adds more formatting logs, you can get it by: :CocCommand workspace.showOutput - coc-pyright-formatting.

   through which you can tell if black is loaded and run correctly.

5. Some more info

   Apart from using "coc.preferences.formatOnSaveFiletypes": ["python"] as mentioned above, also see this issue comment and another issue comment:

   The latest coc has added coc.preferences.willSaveHandlerTimeout, the default is 500ms, you can increase this time limitation.

   This is useful especially when you have very large files, which takes long to format.

Yes I have referenced a few issue comments where the actually instructions are. Maybe they should have a more detailed documentation :)

Answer 2

I had the exact same issue. I solved it as below:

1. Don't use black and isort from inside coc. Coc timeout issue mentioned by @Gorden Bai seems unresolved. My coc-settings.json:

{
    "python.sortImports.path": "/usr/bin/isort",
    "coc.preferences.willSaveHandlerTimeout": 1000,
    // this is required. Else coc looks for autopep8
    "python.formatting.provider": "black",
    "python.formatting.blackPath": "/usr/bin/black",
    // removed python from below to run black and isort independently
    "coc.preferences.formatOnSaveFiletypes": [
        "json",
        "markdown"
    ],
    "coc.source.around.firstMatch": false,
    "pyright.enable": true,
    "python.pythonPath": "/usr/bin/python",
    "python.linting.pylintEnabled": false,
    "python.linting.flake8Enabled": true,
    "python.linting.flake8Path": "flake8",
    "python.linting.enabled": true 
}

2. In init.vim:

call plug#begin('~/.vim/plugged')
Plug 'psf/black', { 'branch': 'main' }
Plug 'fisadev/vim-isort'
call plug#end()

" This triggers all formatting before coc linter is triggered
aug python
    au!
    autocmd BufWritePre *.py Isort
    autocmd BufWritePre *.py Black
aug END

P.S. I am not using virtual environment.

Answer 3

You don't really need coc to format on save.

See the official document: https://black.readthedocs.io/en/stable/integrations/editors.html#vim

After install black as a vim plugin, add this line in your .vimrc

autocmd BufWritePre *.py execute ':Black'

Or as @D.Ben Knoble pointed out

autocmd BufWritePre *.py Black