python filetype nil bug

Reproduce the error by opening a .py file with Neovim 0.11, then inspect lua/ale/lsp.lua around the send_message and initialization paths at lines 135 and 88. Compare the message reaching Neovim's runtime/lua/vim/lsp/rpc.lua:281 and verify that Python linting no longer triggers the table-key serialization error.

Information

neovim 0.11

Operating System: macos 15.4

What went wrong

                 Error executing vim.schedule lua callback: function ale#lsp#CallInitCallbacks[11]..<lambda>38[1]..ale#lsp_linter#OnInit[7]..ale#lsp#UpdateConfig[10]..ale#lsp#Send, line 12: Vim(return):E5108: Error executing lua ...lar/neovim/0.11.0/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/0.11.0/share/nvim/runtime/lua/vim/lsp/rpc.lua:281: in function 'notify'
.../neovim/0.11.0/share/nvim/runtime/lua/vim/lsp/client.lua:766: in function 'notify'
...rs/chenxu/software/nvim/lazy/plugins/ale/lua/ale/lsp.lua:135: in function 'send_message'
[string "luaeval()"]:1: in main chunk
[C]: in function 'ale#lsp#CallInitCallbacks'
...rs/chenxu/software/nvim/lazy/plugins/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'
...rs/chenxu/software/nvim/lazy/plugins/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

only python file cause this errors
open a .py file

: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']
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 = '--max-line-length=200 --indent-size=2'
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 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 = '%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 = v:false
let g:ale_fixers = {}
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 = {'c': ['ccls', 'cspell'], 'sh': ['cspell'], 'markdown': ['languagetool'], 'lua': ['cspell'], 'asciidoc': ['languagetool'], 'rubyinfo': ['cspell'], 'cpp': ['ccls', 'cspell', 'clangtidy', 'cc', 'cpplint', 'flawfinder'], 'ruby': ['cspell']}
let g:ale_list_vertical = v:false
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 = 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 = 'disabled'
let g:ale_warn_about_trailing_blank_lines = v:true
let g:ale_warn_about_trailing_whitespace = v:true

Command History:

(finished - exit code 0) ['/bin/zsh', '-c', '''pylint'' --version']

<<>>
pylint 3.3.6
astroid 3.3.9
Python 3.13.3 (main, Apr 8 2025, 13:54:08) [Clang 16.0.0 (clang-1600.0.26.6)]
<<>>

(executable check - success) flake8
(finished - exit code 0) ['/bin/zsh', '-c', 'cd ''/Users/chenxu/cx_rc'' && ''flake8'' --version']

<<>>
7.2.0 (mccabe: 0.7.0, pycodestyle: 2.13.0, pyflakes: 3.3.2) CPython 3.13.3 on
Darwin
<<>>

(executable check - success) mypy
(finished - exit code 0) ['/bin/zsh', '-c', 'cd ''/Users/chenxu/cx_rc'' && ''mypy'' --show-column-numbers --shadow-file ''/Users/chenxu/cx_rc/config/nvim/lua/plugins/aa.py'' ''/var/folders/05/dfw4d4ds0nx2xyyn7yt5ky3r0000gn/T/nvim.chenxu/55tP49/2/aa.py'' ''/Users/chenxu/cx_rc/config/nvim/lua/plugins/aa.py''']

<<>>
Success: no issues found in 1 source file
<<>>

(executable check - success) pylint
(finished - exit code 0) ['/bin/zsh', '-c', 'cd ''/Users/chenxu/cx_rc'' && ''pylint'' --output-format text --msg-template="{path}:{line}:{column}: {msg_id} ({symbol}) {msg}" --reports n --from-stdin ''/Users/chenxu/cx_rc/config/nvim/lua/plugins/aa.py'' < ''/var/folders/05/dfw4d4ds0nx2xyyn7yt5ky3r0000gn/T/nvim.chenxu/55tP49/3/aa.py''']

<<>>

---

Your code has been rated at 10.00/10 (previous run: 10.00/10, +0.00)

<<>>

(executable check - success) pyright-langserver
(executable check - success) ruff
(finished - exit code 0) ['/bin/zsh', '-c', 'cd ''/Users/chenxu/cx_rc'' && ''ruff'' --version']

<<>>
ruff 0.11.4
<<>>

(finished - exit code 1) ['/bin/zsh', '-c', 'cd ''/Users/chenxu/cx_rc'' && ''ruff'' check -q --no-fix --output-format json-lines --stdin-filename ''/Users/chenxu/cx_rc/config/nvim/lua/plugins/aa.py'' - < ''/var/folders/05/dfw4d4ds0nx2xyyn7yt5ky3r0000gn/T/nvim.chenxu/55tP49/4/aa.py''']

<<>>
{"cell":null,"code":"F401","end_location":{"column":13,"row":1},"filename":"/Users/chenxu/cx_rc/config/nvim/lua/plugins/aa.py","fix":{"applicability":"safe","edits":[{"content":"","end_location":{"column":1,"row":2},"location":{"column":1,"row":1}}],"message":"Remove unused import: numpy"},"location":{"column":8,"row":1},"message":"numpy imported but unused","noqa_row":1,"url":"https://docs.astral.sh/ruff/rules/unused-import"}
<<>>

(finished - exit code 1) ['/bin/zsh', '-c', 'cd ''/Users/chenxu/cx_rc'' && ''flake8'' --max-line-length=200 --indent-size=2 --format=default --stdin-display-name ''/Users/chenxu/cx_rc/config/nvim/lua/plugins/aa.py'' - < ''/var/folders/05/dfw4d4ds0nx2xyyn7yt5ky3r0000gn/T/nvim.chenxu/55tP49/5/aa.py''']

<<>>
/Users/chenxu/cx_rc/config/nvim/lua/plugins/aa.py:1:1: F401 'numpy' imported but unused
<<>>