How to use pylint within a virtualenv? neovim + ale + pylint

[landonstewart]

Hello,

I'm hoping to use ale + pylint within a virtual environment without having to install pylint into every virtualenv I'm working in at the time. When I use import <something> that's only installed within the virtualenv it can't find it because ale (or pylint) is not using the virtual environment that neovim's :CheckHealth reports. For example while editing a new python script within a virtualenv where gunicorn is installed I see import-error: Unable to import 'gunicorn'.

g:python3_host_prog is set to "/opt/homebrew/bin/python3"
pylint is installed in the system environment
neovim is installed in the system environment

I've tried setting g:ale_python_auto_virtualenv to 1 but this has no effect.
I've tried setting g:ale_virtualenv_dir_names to '[]' but this has no effect.

The problem I'm having seems similar to #1777 but my issue is much simpler than that. I just want to not have to install pylint inside every virtualenv I'm coding within.

Perhaps there's an argument for pylint I'm missing that will tell it to use the virtualenv I'm working in? I read the massive number of lines from pylint --help and didn't see anything applicable in there.

Before entering virtual environment:

➜ pip freeze | egrep '(neovim|pylint|gunicorn)'
neovim==0.3.1
pylint==2.16.2

After entering virtual environment (neither of the above are installed - this is on purpose):

(.venv) ➜ pip freeze | egrep '(neovim|pylint|gunicorn)'
gunicorn==20.1.0

neovim config:

let g:python3_host_prog = '/opt/homebrew/bin/python3'

" Show linting only in the status bar
let g:ale_virtualtext_cursor = 0

let g:ale_linters = {
\   '*': ['remove_trailing_lines', 'trim_whitespace'],
\   'python': ['pylint'],
\}

" Ale Fixing
let g:ale_fix_on_save = 1
let g:ale_fixers = {
\   'python': ['black'],
\}

ALEInfo:

 Current Filetype: python
Available Linters: ['bandit', 'cspell', 'flake8', 'flakehell', 'jedils', 'mypy', 'prospector', 'pycln', 'pycodestyle', 'pydocstyle', 'pyflakes', 'pylama', 'pylint', 'pylsp', 'pyre'
, 'pyright', 'refurb', 'ruff', 'unimport', 'vulture']
  Enabled Linters: ['pylint']
  Ignored Linters: []
 Suggested Fixers:
  'add_blank_lines_for_python_control_statements' - Add blank lines before control statements.
  'autoflake' - Fix flake issues with autoflake.
  'autoimport' - Fix import issues with autoimport.
  'autopep8' - Fix PEP8 issues with autopep8.
  'black' - Fix PEP8 issues with black.
  'isort' - Sort Python imports with isort.
  'pycln' - remove unused python import statements
  'pyflyby' - Tidy Python imports with pyflyby.
  'remove_trailing_lines' - Remove all blank lines at the end of a file.
  'reorder-python-imports' - Sort Python imports with reorder-python-imports.
  'ruff' - A python linter/fixer for Python written in Rust
  'trim_whitespace' - Remove all trailing whitespace characters at the end of every line.
  'yapf' - Fix Python files with yapf.
 Linter Variables:
let g:ale_python_auto_pipenv = 0
let g:ale_python_auto_poetry = 0
let g:ale_python_auto_virtualenv = 0
let g:ale_python_pylint_auto_pipenv = 0
let g:ale_python_pylint_auto_poetry = 0
let g:ale_python_pylint_change_directory = 1
let g:ale_python_pylint_executable = 'pylint'
let g:ale_python_pylint_options = ''
let g:ale_python_pylint_use_global = 0
let g:ale_python_pylint_use_msg_id = 0
 Global Variables:
let g:ale_cache_executable_check_failures = v:null
let g:ale_change_sign_column_color = 0
let g:ale_command_wrapper = ''
let g:ale_completion_delay = v:null
let g:ale_completion_enabled = 0
let g:ale_completion_max_suggestions = v:null
let g:ale_disable_lsp = 0
let g:ale_echo_cursor = 1
let g:ale_echo_msg_error_str = 'Error'
let g:ale_echo_msg_format = '%code: %%s'
let g:ale_echo_msg_info_str = 'Info'
let g:ale_echo_msg_warning_str = 'Warning'
let g:ale_enabled = 1
let g:ale_fix_on_save = 1
let g:ale_fixers = {'python': ['black']}
let g:ale_history_enabled = 1
let g:ale_history_log_output = 1
let g:ale_keep_list_window_open = 0
let g:ale_lint_delay = 200
let g:ale_lint_on_enter = 1
let g:ale_lint_on_filetype_changed = 1
let g:ale_lint_on_insert_leave = 1
let g:ale_lint_on_save = 1
let g:ale_lint_on_text_changed = 'normal'
let g:ale_linter_aliases = {}
let g:ale_linters = {'*': ['remove_trailing_lines', 'trim_whitespace'], 'python': ['pylint']}
let g:ale_linters_explicit = 0
let g:ale_linters_ignore = {}
let g:ale_list_vertical = 0
let g:ale_list_window_size = 10
let g:ale_loclist_msg_format = '%code: %%s'
let g:ale_max_buffer_history_size = 20
let g:ale_max_signs = -1
let g:ale_maximum_file_size = v:null
let g:ale_open_list = 0
let g:ale_pattern_options = v:null
let g:ale_pattern_options_enabled = v:null
let g:ale_root = {}
let g:ale_set_balloons = 0
let g:ale_set_highlights = 1
let g:ale_set_loclist = 1
let g:ale_set_quickfix = 0
let g:ale_set_signs = 1
let g:ale_sign_column_always = 0
let g:ale_sign_error = '>>'
let g:ale_sign_info = '--'
let g:ale_sign_offset = 1000000
let g:ale_sign_style_error = '>>'
let g:ale_sign_style_warning = '--'
let g:ale_sign_warning = '--'
let g:ale_sign_highlight_linenrs = 0
let g:ale_statusline_format = v:null
let g:ale_type_map = {}
let g:ale_use_neovim_diagnostics_api = 0
let g:ale_use_global_executables = v:null
let g:ale_virtualtext_cursor = 0
let g:ale_warn_about_trailing_blank_lines = 1
let g:ale_warn_about_trailing_whitespace = 1
  Command History:
(finished - exit code 0) ['/bin/zsh', '-c', '''pylint'' --version']
<<<OUTPUT STARTS>>>
pylint 2.16.2
astroid 2.14.2
Python 3.11.2 (main, Feb 13 2023, 03:31:04) [Clang 14.0.0 (clang-1400.0.29.202)]
<<<OUTPUT ENDS>>>
(executable check - success) pylint
(finished - exit code 22) ['/bin/zsh', '-c', 'cd ''/Users/lstewart/Projects/LSWAC'' && ''pylint'' --output-format text --msg-template="{path}:{line}:{column}: {msg_id} ({symbol}) {
msg}" --reports n --from-stdin ''/Users/lstewart/Projects/LSWAC/temp.py'' < ''/var/folders/mj/b2t_3cyx5gg9l_tnykyjtqt80000gn/T/nvim.lstewart/7SPaeQ/1/temp.py''']
<<<OUTPUT STARTS>>>
************* Module temp
temp.py:1:0: C0114 (missing-module-docstring) Missing module docstring
temp.py:1:0: E0401 (import-error) Unable to import 'gunicorn'
temp.py:1:0: W0611 (unused-import) Unused import gunicorn
------------------------------------------------------------------
Your code has been rated at 0.00/10 (previous run: 0.00/10, +0.00)

CheckHealth:

...
## Python 3 provider (optional)
  - INFO: Using: g:python3_host_prog = "/opt/homebrew/bin/python3"
  - INFO: Executable: /opt/homebrew/bin/python3
  - INFO: Python version: 3.11.2
  - INFO: pynvim version: 0.4.3
  - OK: Latest pynvim is installed.

## Python virtualenv
  - INFO: $VIRTUAL_ENV is set to: /Users/lstewart/Projects/LSWAC/.venv
  - INFO: Python version: 3.11.2
  - OK: $VIRTUAL_ENV provides :!python.
...

[w0rp]

This is actually an issue with pylint and other tools, and it was seen with VSCode too. microsoft/vscode-python#2336

The only way I know of to get pylint to do the right thing is to install it into every virtualenv. The upside to this is that you can ensure pylint behaves consistently for other users by everyone running the same pylint version in virtualenv.