How to use the Language Server Protocol for Python in Neovim

Question

I've spend quite some time figuring out how to use the Language Server Protocol (LSP) for Python (3) in neovim. Mainly I'm looking for autocompletion with Python 3 and it's modules like PySide2.

Sadly I just can't get my config file (.config/vim/init.vim) to work. I know there are a lot of them on github. But they include so many additional functionality that I've not yet been able to adapt one of the to my needs. And some are also outdated.

So here is what I've tried so far:

www.langserver.org has a quite long list of language clients and servers.

I installed Palantirs Language Server Protocol for Python (https://github.com/palantir/python-language-server):

pip3 install 'python-language-server[all]'

In the next step I installed a language client for neovim via vim-plug. Actually I tried several but let's stick to ale for the example (https://github.com/dense-analysis/ale):

call plug#begin('~/.local/share/nvim/plugged')
" Plugins:
Plug 'dense-analysis/ale'

" Initialize plugin system
call plug#end()

And installed it via :PlugInstall

Then the for autocompletion to work a setting must be made before Ale is loaded:

" initialize before ale is loaded
let g:ale_completion_enabled = 1

For usage with Omnicompletion one more setting is needed:

set omnifunc=ale#completion#OmniFunc

And after some more googling I read that I've to register the language server (https://vi.stackexchange.com/questions/20958/use-the-pyls-python-lsp-with-ale-on-neovim):

if executable('pyls')
    au User lsp_setup call lsp#register_server({
        \ 'name': 'pyls',
        \ 'cmd': {server_info->['pyls']},
        \ 'whitelist': ['python'],
        \ })
endif

This gives me the final init.vim:

" Specify a directory for plugins
" - For Neovim: ~/.local/share/nvim/plugged
" - Avoid using standard Vim directory names like 'plugin'
call plug#begin('~/.local/share/nvim/plugged')
" Plugins go here:

" Language Server Client
Plug 'dense-analysis/ale'

" initialize before ale is loaded
" is that the right spot?
let g:ale_completion_enabled = 1

" Initialize plugin system
call plug#end()

set omnifunc=ale#completion#OmniFunc

" register the language server
if executable('pyls')
    au User lsp_setup call lsp#register_server({
        \ 'name': 'pyls',
        \ 'cmd': {server_info->['pyls']},
        \ 'whitelist': ['python'],
        \ })
endif

If I now open a file like the following and press Ctrl + N for completion after PySide2. I only get the following screen in nvim:

#!/usr/bin/env python

>>from PySide2.usr 
--             usr            
~              bin            
~              env            
~              python         
~              from           
~              PySide2        
~

It's just a list of the word that already appeared in the file - just like normal Omnicompletion but not the modules from the PySide2 lib.

I'm just looking for a minimalistic configuration to enable autocompletion via LSP.

For one thing... To activate Omni completion, you need to use <C-x><C-o>, not just <C-n> which will actually only complete from symbols on the same file (which is what you're seeing there...) Not sure if that's the only issue, but I'd start there 😁 — filbranden
– filbranden, Commented Dec 21, 2019 at 16:47
Thanks you so much for this hint! So far I've only been using the jedi-vim plugin and sometimes it completed names from Python modules and sometimes not. I never understood why it behaved kind of randomly. But after your hint and a bit more reading it totally makes sense now. <C-n> only completes from the local file and <C-x><C-o> also looks into the modules. Even the jedi-vim plugin without LSP has become so much more useful to me now. Big thanks! — stack_anonymous
– stack_anonymous, Commented Dec 22, 2019 at 18:04
Did it solve your issue? If so, feel free to post a self-answer with the details... — filbranden
– filbranden, Commented Dec 22, 2019 at 18:05
I just tried it with LSP and the ALE plugin. Here I haven't got it working yet. But jedi-vim is now already pretty close to what I've been looking for. But I'll post a reply if I can make it work with ALE as well. — stack_anonymous
– stack_anonymous, Commented Dec 22, 2019 at 18:12
Consider trying coc.nvim, it's a modern plug-in directly aimed at LSPs. Please note it's not NeoVim-only (as the name might suggest), it works on Vim 8 as well. — filbranden
– filbranden, Commented Dec 22, 2019 at 18:22

Ethan · Accepted Answer · 2020-01-05 13:01:22Z

7

coc.nvim is much easier to setup than ale for lsp

vimrc:

Plug 'neoclide/coc.nvim', {'branch': 'release'}

then from within vim8/nvim:

:PlugInstall
:CocInstall coc-python

answered Jan 5, 2020 at 13:01

Ethan

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1 Comment

Michael F Over a year ago

coc-python is not maintained since November 2020.

stack_anonymous · Accepted Answer · 2019-12-24 16:59:58Z

2

Self reply 1:

I haven't given up on this yet. I found the following useful link and want to share this: https://yufanlu.net/2018/09/03/neovim-python/

Actually not everything works perfectly with the setup shown in the link, but it already showed me some mistakes I made.

But the ALE plugin in the link is outdate, so you have to change the following line:

Plug 'w0rp/ale'

to this line:

Plug 'dense-analysis/ale'

I assume.

edited Dec 24, 2019 at 16:59

answered Dec 24, 2019 at 16:25

stack_anonymous

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Comments

d33tah · Accepted Answer · 2021-12-07 16:45:30Z

2

Note that the latest versions of neovim have language server (LSP) support built in. My relevant part of ~/.vimrc looks like this:

call plug#begin('~/.vim/plugged')
:Plug 'neovim/nvim-lsp'
call plug#end()

lua<<
    local status, nvim_lsp = pcall(require, "nvim_lsp")
    if(status) then
        nvim_lsp.pyls.setup{}
    end
.

While at it, I totally recommend adding nnoremap <silent> <F5> <cmd>lua vim.lsp.buf.formatting()<CR>. Having F5 bound to reformat capability bought me into LSP ecosystem immediately.

answered Dec 7, 2021 at 16:45

d33tah

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stack_anonymous · Accepted Answer · 2019-12-25 16:36:47Z

1

Self reply 2:

Ok, no LSP yet for Python. But I got the feature working that is most important to me, autocompletion. Actually this requires three plugins: jedi-vim, deoplete.nvim and deoplete-jedi. Now nvim shows potential syntax as you're typing. The config file is still quite easy:

call plug#begin('~/.local/share/nvim/plugged')
" Plugins:

" autocompletion for Python
Plug 'davidhalter/jedi-vim'

" show autocompletion
if has('nvim')
  Plug 'Shougo/deoplete.nvim', { 'do': ':UpdateRemotePlugins' }
else
  Plug 'Shougo/deoplete.nvim'
  Plug 'roxma/nvim-yarp'
  Plug 'roxma/vim-hug-neovim-rpc'
endif
" further plugin for autocompletion
Plug 'deoplete-plugins/deoplete-jedi'

" Initialize plugin system
call plug#end()

" enable deoplete
let g:deoplete#enable_at_startup = 1

The first time autocompletion is used, there's a littel lag, as it need some time to load. But afterwards the suggestions are shown quickly. You can switch through the list via the arrow keys or <Ctrl>-Nand <Ctrl>-P, finally <Enter> pasts the selected expression.

And of course nvim needs Python to be available:

pip3 install --user neovim

edited Dec 25, 2019 at 16:36

answered Dec 24, 2019 at 16:56

stack_anonymous

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2 Comments

Jay Lee Over a year ago

I'm using coc.nvim with Python LSP and it works great.

jdhao Over a year ago

You should put all your answers into to one answer instead of two. This is not how stack overflow works.

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