ImportError: cannot import name 'NothingType' from 'attrs'

[mindThomas]

Diagnostic Data

• Python version (& distribution if applicable, e.g., Anaconda): Python 3.12.3
• Type of virtual environment used (e.g., conda, venv, virtualenv, etc.): venv
• Operating system (and version): Ubuntu 24.04
• Version of tool extension you are using: 2026.4.0

Behaviour

After updating the VS Code extension from 2025.2.0 to 2026.4.0 the Black formatter extension is no longer working. Whenever I start VS Code I get errors from the Black formatter that it couldn't start. If I check the output I see the following error messages:

2026-04-30 11:11:28.488 [info] Traceback (most recent call last):
  File "/home/thomas/.vscode-server/extensions/ms-python.black-formatter-2026.4.0/bundled/tool/lsp_server.py", line 74, in <module>
    from pygls.lsp.server import LanguageServer
  File "/home/thomas/.vscode-server/extensions/ms-python.black-formatter-2026.4.0/bundled/libs/pygls/lsp/__init__.py", line 17, in <module>
    import cattrs
  File "/home/thomas/.vscode-server/extensions/ms-python.black-formatter-2026.4.0/bundled/libs/cattrs/__init__.py", line 3, in <module>
    from .converters import BaseConverter, Converter, GenConverter, UnstructureStrategy
  File "/home/thomas/.vscode-server/extensions/ms-python.black-formatter-2026.4.0/bundled/libs/cattrs/converters.py", line 18, in <module>
    from ._compat import (
  File "/home/thomas/.vscode-server/extensions/ms-python.black-formatter-2026.4.0/bundled/libs/cattrs/_compat.py", line 44, in <module>
    from attrs import NOTHING, Attribute, Factory, NothingType, resolve_types
ImportError: cannot import name 'NothingType' from 'attrs' (/usr/lib/python3/dist-packages/attrs/__init__.py)

2026-04-30 11:11:28.495 [info] [Error - 11:11:28 AM] Server process exited with code 1.
2026-04-30 11:11:28.496 [info] [Error - 11:11:28 AM] Server initialization failed.
2026-04-30 11:11:28.497 [info]   Message: Pending response rejected since connection got disposed
  Code: -32097 
2026-04-30 11:11:28.497 [info] [Info  - 11:11:28 AM] Connection to server got closed. Server will restart.
2026-04-30 11:11:28.497 [info] true
2026-04-30 11:11:28.497 [info] [Error - 11:11:28 AM] Black Formatter client: couldn't create connection to server.
2026-04-30 11:11:28.497 [info]   Message: Pending response rejected since connection got disposed
  Code: -32097 
2026-04-30 11:11:28.497 [info] [Error - 11:11:28 AM] Restarting server failed
2026-04-30 11:11:28.497 [info]   Message: Pending response rejected since connection got disposed
  Code: -32097 

Extra details

VS Code version:

Version: 1.109.2 (user setup)
Commit: 591199df409fbf59b4b52d5ad4ee0470152a9b31
Date: 2026-02-10T20:18:23.520Z
Electron: 39.3.0
ElectronBuildId: 13168319
Chromium: 142.0.7444.265
Node.js: 22.21.1
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26200

Installed extensions:

076923.python-image-preview@0.1.2
adrianwilczynski.toggle-hidden@1.0.2
alanzhang.open-symlink-source@0.0.1
althack.ament-task-provider@0.4.1
arturodent.launch-config@0.9.0
augustocdias.tasks-shell-input@1.20.0
azurity.pcd-viewer@0.0.8
bazelbuild.vscode-bazel@0.14.0
bbenoist.doxygen@1.0.0
benjamin-simmonds.pythoncpp-debug@0.3.0
bierner.markdown-preview-github-styles@2.2.0
brobeson.vscode-cmake-lint@1.0.0
cardinal90.multi-cursor-case-preserve@1.0.5
cheshirekow.cmake-format@0.6.11
christian-kohler.path-intellisense@2.10.0
chrmarti.regex@0.6.0
colch.quick-open-prefill-selection@0.2.2
cschlosser.doxdocgen@1.4.0
dan-c-underwood.arm@1.7.4
davidanson.vscode-markdownlint@0.61.2
deitry.colcon-helper@1.3.0
docker.docker@0.18.0
donjayamanne.githistory@0.6.20
dotjoshjohnson.xml@2.5.1
drblury.protobuf-vsc@1.6.6
drcika.apc-extension@0.4.1
dunstontc.dark-plus-syntax@0.2.11
eamodio.gitlens@17.12.2
eclipse-cdt.memory-inspector@1.2.0
eclipse-cdt.serial-monitor@2.0.0
editorconfig.editorconfig@0.18.2
emeraldwalk.runonsave@1.0.3
esbenp.prettier-vscode@12.4.0
fehey.brackets-light-pro@0.4.6
foxundermoon.shell-format@7.2.8
freeidom.vscode-friendly-ui@0.0.5
george-alisson.html-preview-vscode@0.2.5
github.copilot-chat@0.37.5
github.github-vscode-theme@6.3.5
github.vscode-github-actions@0.31.5
github.vscode-pull-request-github@0.128.0
goessner.mdmath@2.7.4
gruntfuggly.activitusbar@0.0.47
gruntfuggly.auto-snippet@0.0.11
hediet.vscode-drawio@1.9.0
helly25.helly25iwyu@0.0.19
hoangkimlai.ipython@2025.8.0
hoddy3190.sync-extensions@1.0.0
iliazeus.vscode-ansi@1.1.7
intellect-ind-in.cmake-formatter@0.0.2
james-yu.latex-workshop@10.14.0
jebbs.plantuml@2.18.1
jomeinaster.bracket-peek@1.4.4
jota0222.multi-formatter@1.6.2
k--kato.intellij-idea-keybindings@1.7.7
kbysiec.vscode-search-everywhere@2.1.0
leeh.vcl-extension@1.1.9
llvm-vs-code-extensions.vscode-clangd@0.4.0
louiswt.regexp-preview@0.1.5
ludenstian.autotask@5.0.1
mads-hartmann.bash-ide-vscode@1.43.0
marus25.cortex-debug@1.12.1
mateocerquetella.xcode-12-theme@5.0.1
mcu-debug.debug-tracker-vscode@0.0.15
mcu-debug.memory-view@0.0.29
mcu-debug.peripheral-viewer@1.6.1
mcu-debug.rtos-views@0.0.15
meezilla.json@0.1.2
meisammafi.clion-plus-theme@0.0.1
mhutchie.git-graph@1.30.0
mkhl.shfmt@1.5.2
morningfrog.urdf-visualizer@5.1.0
ms-azuretools.vscode-containers@2.4.3
ms-azuretools.vscode-docker@2.0.0
ms-python.black-formatter@2026.4.0
ms-python.debugpy@2026.4.0
ms-python.flake8@2026.4.0
ms-python.isort@2026.4.0
ms-python.mypy-type-checker@2026.4.0
ms-python.python@2026.4.0
ms-python.vscode-pylance@2026.2.1
ms-python.vscode-python-envs@1.20.1
ms-toolsai.datawrangler@1.24.1
ms-toolsai.jupyter@2025.9.1
ms-toolsai.jupyter-keymap@1.1.2
ms-toolsai.jupyter-renderers@1.3.0
ms-toolsai.vscode-jupyter-cell-tags@0.1.9
ms-toolsai.vscode-jupyter-slideshow@0.1.6
ms-vscode-remote.remote-containers@0.457.0
ms-vscode-remote.remote-ssh@0.122.0
ms-vscode-remote.remote-ssh-edit@0.87.0
ms-vscode-remote.remote-wsl@0.104.3
ms-vscode-remote.vscode-remote-extensionpack@0.26.0
ms-vscode.cmake-tools@1.23.52
ms-vscode.cpp-devtools@0.4.7
ms-vscode.cpptools@1.32.2
ms-vscode.cpptools-extension-pack@1.5.1
ms-vscode.cpptools-themes@2.0.0
ms-vscode.hexeditor@1.11.1
ms-vscode.remote-explorer@0.5.0
ms-vscode.remote-server@1.5.3
ms-vscode.vscode-embedded-tools@0.8.0
ms-vscode.vscode-serial-monitor@0.13.1
mtsmfm.vscode-stl-viewer@0.3.0
njpwerner.autodocstring@0.6.1
nvidia.isaacsim-vscode-edition@0.3.0
openai.chatgpt@26.422.71525
outofsync42.select-compare-tabs@1.0.3
paragdiwan.gitpatch@0.2.1
particle.particle-vscode-theme@1.16.48
piotrpalarz.vscode-gitignore-generator@1.0.4
platformio.platformio-ide@3.3.4
pokowaka.pokowaka-iwyu@1.0.3
ranch-hand-robotics.rde-pack@1.0.0
ranch-hand-robotics.rde-ros-2@1.2.1
redhat.vscode-xml@0.29.2
redhat.vscode-yaml@1.22.0
repreng.csv@1.3.0
rioj7.command-variable@1.70.0
roehling.eclipse-color-theme@0.1.3
ryuta46.multi-command@1.6.0
sanjulaganepola.github-local-actions@1.2.5
saoudrizwan.claude-dev@3.81.0
sh4dow.theme-notepadplusplusremixed@1.0.3
shayanahmedkhan.notepadpp-color-theme@0.2.0
shd101wyy.markdown-preview-enhanced@0.8.24
shibayu36.search-in-current-file@0.0.2
sleistner.vscode-fileutils@3.10.3
stmicroelectronics.stm32-vscode-extension@3.8.0
stmicroelectronics.stm32cube-ide-build-analyzer@1.2.0
stmicroelectronics.stm32cube-ide-build-cmake@1.44.0
stmicroelectronics.stm32cube-ide-bundles-manager@1.2.0
stmicroelectronics.stm32cube-ide-clangd@1.0.4
stmicroelectronics.stm32cube-ide-core@1.2.1
stmicroelectronics.stm32cube-ide-debug-core@1.2.2
stmicroelectronics.stm32cube-ide-debug-generic-gdbserver@1.2.2
stmicroelectronics.stm32cube-ide-debug-jlink-gdbserver@1.2.2
stmicroelectronics.stm32cube-ide-debug-stlink-gdbserver@1.2.2
stmicroelectronics.stm32cube-ide-project-manager@1.2.1
stmicroelectronics.stm32cube-ide-registers@1.2.1
stmicroelectronics.stm32cube-ide-rtos@1.2.0
streetsidesoftware.code-spell-checker@4.5.6
subframe7536.custom-ui-style@0.6.9
swashata.beautiful-ui@1.7.0
takumii.markdowntable@0.13.0
tatsy.vscode-3d-preview@0.2.4
timonwong.shellcheck@0.39.3
trond-snekvik.gnu-mapfiles@1.1.0
twxs.cmake@0.0.17
uloco.theme-bluloco-light@3.7.5
usernamehw.errorlens@3.28.0
visualcodesearch.visual-code-search@0.2.0
vivaxy.vscode-conventional-commits@1.27.0
vscode-icons-team.vscode-icons@12.18.0
vscode-snippet.snippet@1.2.0
xaver.clang-format@1.9.0
yutengjing.power-edit@1.4.3
yzhang.markdown-all-in-one@3.6.3
zixuanwang.linkerscript@1.0.4

[rcostanza]

Same thing here. Tried switching the extension to its pre-release version 2026.5.11201012 but the error persists.

Version: 1.118.1 (user setup)
Commit: 034f571df509819cc10b0c8129f66ef77a542f0e
Date: 2026-04-29T17:36:44+03:00 (23 hrs ago)
Electron: 39.8.8
ElectronBuildId: 13870025
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26200

[mpearson]

It looks like the new release of the extension 2026.4.0 requires black >= 26.1.0. In my codebase we're using black 24.4.2 and can't just upgrade at the drop of a hat to suit random IDE extensions. Downgrading to the previous release of the extension, 2025.2.0 fixed the issue for me. So if you have your extension configured to use something other than the bundled version of black, and you don't strictly need to use an older version, that should fix it.

[taesungh]

Hi @bschnurr, I see you have a draft PR, is there any update on when that will be ready for review?

[bschnurr]

@mpearson extension version 2026.5.11321003 i'm not seeing an issue with black 24.4.2

settings.json

 "black-formatter.path": [
        "${workspaceFolder}/.venv/Scripts/python.exe",
        "-m",
        "black"
    ]

[taesungh]

My understanding is this issue surfaces when the selected Python environment specifically has an older version of attrs, e.g.

>>> import attrs
>>> attrs.__version__
'24.2.0'

and with setting "black-formatter.importStrategy": "fromEnvironment", even with newer black >= 26.1.0

Situation being it's not feasible to update attrs due to external reasons (e.g. dependency tree for corporate setup).

[mindThomas]

In our case, we are using attrs==23.2.0 (on Ubuntu 24.04). I will investigate whether we can upgrade to attrs==26.1.0 which I can confirm addresses the extension problem in version 2026.4.0.