ALE gives an error at Neovim startup #5062
Description
Information
VIM version
NVIM v0.11.5
Build type: Release
LuaJIT 2.1.1761727121
Operating System: Ubuntu 24.04
What went wrong
I have installed Neovim from Linuxbrew and installed all the plugins from scratch via vim-plug (so they are not outdated or something, as of 7 Nov 2025).
At the start, when I open a file, Neovim complains that ALE function violates some Lua/RPC expectations:
Error executing vim.schedule lua callback: function ale#lsp#CallInitCallbacks[11]..<lambda>18[1]..ale#lsp_
linter#OnInit[7]..ale#lsp#UpdateConfig[10]..ale#lsp#Send, line 12: Vim(return):E5108: Error executing lua
...lar/neovim/0.11.5/share/nvim/runtime/lua/vim/lsp/rpc.lua:281: Cannot serialise boolean: table key must
be a number or string
stack traceback:
[C]: in function 'encode'
...lar/neovim/0.11.5/share/nvim/runtime/lua/vim/lsp/rpc.lua:281: in function 'notify'
.../neovim/0.11.5/share/nvim/runtime/lua/vim/lsp/client.lua:773: in function 'notify'
/home/dima/.vim/plugged/ale/lua/ale/lsp.lua:135: in function 'send_message'
[string "luaeval()"]:1: in main chunk
[C]: in function 'ale#lsp#CallInitCallbacks'
/home/dima/.vim/plugged/ale/lua/ale/lsp.lua:88: in function ''
vim/_editor.lua: in function ''
vim/_editor.lua: in function <vim/_editor.lua:0>
stack traceback:
[C]: in function 'ale#lsp#CallInitCallbacks'
/home/dima/.vim/plugged/ale/lua/ale/lsp.lua:88: in function ''
vim/_editor.lua: in function ''
vim/_editor.lua: in function <vim/_editor.lua:0>
Reproducing the bug
- Install Neovim from Linuxbrew
- Install ALE
- Try to open some file, for example, a Python script.
:ALEInfo
Expand
Current Filetype: python
Available Linters: ['bandit', 'cspell', 'flake8', 'flakehell', 'jedils', 'mypy', 'prospector', 'pycln', 'pycodestyle', 'pydocstyle', 'pyflakes', 'pylama', 'pylint', 'pylsp', 'pyre', 'pyrefly', 'pyright', 'refurb', 'ruff', 'unimport', 'vulture']
Linter Aliases:
'jedils' -> ['jedi_language_server']
Enabled Linters: ['flake8', 'mypy', 'pylint', 'pyright', 'ruff']
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
'ruff_format' - Fix python files with the ruff formatter.
'trim_whitespace' - Remove all trailing whitespace characters at the end of every line.
'yapf' - Fix Python files with yapf.
Linter Variables:
" Press Space to read :help for a setting
let g:ale_python_auto_pipenv = v:false
let g:ale_python_auto_poetry = v:false
let g:ale_python_auto_uv = v:false
let g:ale_python_auto_virtualenv = v:false
let g:ale_python_flake8_auto_pipenv = 0
let g:ale_python_flake8_auto_poetry = 0
let g:ale_python_flake8_auto_uv = 0
let g:ale_python_flake8_change_directory = 'project'
let g:ale_python_flake8_executable = 'flake8'
let g:ale_python_flake8_options = ''
let g:ale_python_flake8_use_global = 0
let g:ale_python_mypy_auto_pipenv = 0
let g:ale_python_mypy_auto_poetry = 0
let g:ale_python_mypy_auto_uv = 0
let g:ale_python_mypy_executable = 'mypy'
let g:ale_python_mypy_ignore_invalid_syntax = 0
let g:ale_python_mypy_options = ''
let b:ale_python_mypy_options = '--ignore-missing-imports'
let g:ale_python_mypy_show_notes = 1
let g:ale_python_mypy_use_global = 0
let g:ale_python_pylint_auto_pipenv = 0
let g:ale_python_pylint_auto_poetry = 0
let g:ale_python_pylint_auto_uv = 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
let g:ale_python_pyright_auto_pipenv = 0
let g:ale_python_pyright_auto_poetry = 0
let g:ale_python_pyright_auto_uv = 0
let g:ale_python_pyright_config = {}
let g:ale_python_pyright_executable = 'pyright-langserver'
let g:ale_python_pyright_use_global = 0
let g:ale_python_ruff_auto_pipenv = 0
let g:ale_python_ruff_auto_poetry = 0
let g:ale_python_ruff_auto_uv = 0
let g:ale_python_ruff_change_directory = 1
let g:ale_python_ruff_executable = 'ruff'
let g:ale_python_ruff_options = ''
let g:ale_python_ruff_use_global = 0
Global Variables:
" Press Space to read :help for a setting
let g:ale_cache_executable_check_failures = v:null
let g:ale_change_sign_column_color = v:null
let g:ale_command_wrapper = ''
let g:ale_completion_delay = v:null
let g:ale_completion_enabled = v:false
let g:ale_completion_max_suggestions = v:null
let g:ale_disable_lsp = 'auto'
let g:ale_echo_cursor = v:true
let g:ale_echo_msg_error_str = 'Error'
let g:ale_echo_msg_format = '[%linter%] %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 = {}
let b:ale_fixers = ['isort', 'black']
let g:ale_history_enabled = v:true
let g:ale_info_default_mode = 'preview'
let g:ale_history_log_output = v:true
let g:ale_keep_list_window_open = 0
let g:ale_lint_delay = 200
let g:ale_lint_on_enter = v:true
let g:ale_lint_on_filetype_changed = v:true
let g:ale_lint_on_insert_leave = v:true
let g:ale_lint_on_save = v:true
let g:ale_lint_on_text_changed = 'normal'
let g:ale_linter_aliases = {}
let g:ale_linters = {}
let g:ale_linters_explicit = v:false
let g:ale_linters_ignore = {}
let g:ale_list_vertical = v:false
let g:ale_list_window_size = 10
let g:ale_loclist_msg_format = '[%linter%] %code: %%s'
let g:ale_max_buffer_history_size = 20
let g:ale_max_signs = v:null
let g:ale_maximum_file_size = v:null
let g:ale_open_list = v:false
let g:ale_pattern_options = v:null
let g:ale_pattern_options_enabled = v:null
let g:ale_root = {}
let g:ale_set_balloons = v:false
let g:ale_set_highlights = v:true
let g:ale_set_loclist = v:true
let g:ale_set_quickfix = v:false
let g:ale_set_signs = v:true
let g:ale_sign_column_always = v:null
let g:ale_sign_error = v:null
let g:ale_sign_info = v:null
let g:ale_sign_offset = v:null
let g:ale_sign_style_error = v:null
let g:ale_sign_style_warning = v:null
let g:ale_sign_warning = v:null
let g:ale_sign_highlight_linenrs = v:null
let g:ale_type_map = {}
let g:ale_use_neovim_diagnostics_api = v:true
let g:ale_use_global_executables = v:null
let g:ale_virtualtext_cursor = 'all'
let g:ale_warn_about_trailing_blank_lines = v:true
let g:ale_warn_about_trailing_whitespace = v:true
Command History:
(finished - exit code 127) ['/bin/zsh', '-c', '''pylint'' --version']
<<>>
zsh:1: command not found: pylint
<<>>
(executable check - success) flake8
(finished - exit code 0) ['/bin/zsh', '-c', 'cd ''/home/dima/Work/um02-open-interfaces'' && ''flake8'' --version']
<<>>
7.2.0 (mccabe: 0.7.0, pycodestyle: 2.13.0, pyflakes: 3.3.2) CPython 3.13.2 on
Linux
<<>>
(executable check - success) mypy
(finished - exit code 1) ['/bin/zsh', '-c', 'cd ''/home/dima/Work/um02-open-interfaces'' && ''mypy'' --ignore-missing-imports --show-column-numbers --shadow-file ''/home/dima/Work/um02-open-interfaces/tests/lang_python/test_examples.py'' ''/tmp/nvim.dima/0XM3XG/3/test_examples.py'' ''/home/dima/Work/um02-open-interfaces/tests/lang_python/test_examples.py''']
<<>>
tests/lang_python/test_examples.py:8:2: error: Name "pytest" is not defined [name-defined]
Found 1 error in 1 file (checked 1 source file)
<<>>
(executable check - failure) pylint
(executable check - success) pyright-langserver
(executable check - failure) ruff
(finished - exit code 1) ['/bin/zsh', '-c', 'cd ''/home/dima/Work/um02-open-interfaces'' && ''flake8'' --format=default --stdin-display-name ''/home/dima/Work/um02-open-interfaces/tests/lang_python/test_examples.py'' - < ''/tmp/nvim.dima/0XM3XG/4/test_examples.py''']
<<>>
/home/dima/Work/um02-open-interfaces/tests/lang_python/test_examples.py:8:2: F821 undefined name 'pytest'
<<>>