OSError: [Errno 36] File name too long

[donverduyn]

Type: Bug

• Configure black formatter extension to be used for formatting
• Open a jupyter notebook inside a dev container on a remote host (over a vscode tunnel)
• Observe that the following error is shown in the logs:
  OSError: [Errno 36] File name too long: '/dev-container+7b22686f737450617468223a222f686f6d652f646f6e6e792f50726f6a656374732f776f72647365617263682d637370222c226c6f63616c446f636b6572223a66616c73652c22636f6e66696746696c65223a7b22246d6964223a312c2270617468223a222f686f6d652f646f6e6e792f50726f6a656374732f776f72647365617263682d6373702f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c22736368656d65223a227673636f64652d66696c65486f7374227d7d@tunnel+

Fixed in:
https://github.com/donverduyn/vscode-black-formatter/tree/bugfix/filename-too-long

Extension version: 2026.4.0
VS Code version: Code 1.118.1 (Universal) (034f571df509819cc10b0c8129f66ef77a542f0e, 2026-04-29T17:36:44+03:00)
OS version: Darwin arm64 24.6.0
Modes:
Connection to 'dev-container+7b22686f737450617468223a222f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f77222c226c6f63616c446f636b6572223a66616c73652c2273657474696e6773223a7b22636f6e74657874223a226465736b746f702d6c696e7578227d2c22636f6e66696746696c65223a7b22246d6964223a312c22667350617468223a222f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f772f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2265787465726e616c223a2266696c653a2f2f2f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f772f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2270617468223a222f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f772f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c22736368656d65223a2266696c65227d7d' could not be established
Remote OS version: Linux x64 6.17.9-76061709-generic

System Info

Item	Value
CPUs	Apple M1 (8 x 2400)
GPU Status	2d_canvas: enabled GPU0: VENDOR= 0x106b [Google Inc. (Apple)], DEVICE=0x0000 [ANGLE (Apple, ANGLE Metal Renderer: Apple M1, Version 15.7 (Build 24G222))], DRIVER_VENDOR=Apple, DRIVER_VERSION=15.7 ACTIVE Machine model name: MacBookAir Machine model version: 10.1 direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: enabled_on trees_in_viz: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	8, 8, 7
Memory (System)	16.00GB (0.07GB free)
Process Argv	--crash-reporter-id 9e5b74d3-969a-40a2-b2e5-561acacb1e0a
Screen Reader	no
VM	0%

Connection to 'dev-container+7b22686f737450617468223a222f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f77222c226c6f63616c446f636b6572223a66616c73652c2273657474696e6773223a7b22636f6e74657874223a226465736b746f702d6c696e7578227d2c22636f6e66696746696c65223a7b22246d6964223a312c22667350617468223a222f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f772f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2265787465726e616c223a2266696c653a2f2f2f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f772f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2270617468223a222f55736572732f646f6e6e792f50726f6a656374732f736f756c676c6f772f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c22736368656d65223a2266696c65227d7d' could not be established

Item	Value
Remote	Dev Container: Micromamba (Python 3) @ pop-os
OS	Linux x64 6.17.9-76061709-generic
CPUs	AMD Ryzen 5 3600 6-Core Processor (12 x 2200)
Memory (System)	31.25GB (18.90GB free)
VM	0%

A/B Experiments

vsliv368cf:30146710
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31463988
aj953862:31281341
b6b4d950:31327385
6abeh943:31336334
envsactivate1:31505457
cloudbuttont:31379625
3efgi100_wstrepl:31403338
ec5jj548:31422691
cp_cls_t_966_ss:31454198
inlinechat_v2_hd992725:31505030
8hhj4413:31478653
ge8j1254_inline_auto_hint_haiku:31490510
38bie571_auto:31478678
cp_cls_t_1081:31454832
conptydll_true:31498968
ia-use-proxy-models-svc:31452481
e9c30283:31461165
test_treatment2:31471001
46204921:31447328
control_6dc23131:31497324
idci7584:31464702
e3e4d672:31494082
ei9d7968:31496641
nes-extended-on:31455476
chat:31457767
8hig5102:31480529
89g7j272:31506664
7e187181:31503455
i2gc6536:31499202
ghj88844:31499326
ec1eg703:31491645
client_tst_t:31495907
ddid_c:31478207
hmra_i5g22:31505557
getcmakediagnosticsoff:31489825
a2954740:31507016
pro_large_t:31499376
cp_cls_c_1082:31504161
logging_enabled_new:31498466
j0d79568:31499440
nes-dist-check-on:31503267
748c7209:31497895
32d76977:31505232
e8jdj427:31505714
539gd155_c:31506875

[donverduyn]

Updating the package @vscode/common-python-lsp to 0.5.2, resolves this issue.

[edvilme]

Yes, thanks @donverduyn
We are upgrading to the new version in #754

[donverduyn]

fixed in #754

[ahemwe]

I'm still facing this particular issue.
Tried stable (2026.4.0) and pre-release version of the extension (2026.7.11811009) where the later one should contain mentioned fix #754.
@edvilme .
Anything I miss?

Log

2026-07-03 06:54:59.392 [info] /usr/local/bin/python -m black --stdin-filename //dev-container+7b22686f737450617468223a225c5c5c5c77736c2e6c6f63616c686f73745c5c5562756e747532342d56504e2d4b69745c5c686f6d655c5c7a3132343038395c5c6769745f77735c5c446174615f536f6c7574696f6e735f44617461627269636b73222c226c6f63616c446f636b6572223a66616c73652c22636f6e66696746696c65223a7b22246d6964223a312c2270617468223a222f686f6d652f7a3132343038392f6769745f77732f446174615f536f6c7574696f6e735f44617461627269636b732f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c22736368656d65223a227673636f64652d66696c65486f7374227d7d/workspaces/foo/bar.py -
2026-07-03 06:54:59.392 [info] CWD Black Formatter: /workspaces/foo
2026-07-03 06:54:59.395 [info] [Error - 6:54:59 AM] Traceback (most recent call last):
  File "/home/user/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/libs/vscode_common_python_lsp/server.py", line 383, in execute_tool
    result = run_module(
             ^^^^^^^^^^^
  File "/home/user/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/libs/vscode_common_python_lsp/runner.py", line 89, in run_module
    runpy.run_module(module, run_name="__main__")
  File "<frozen runpy>", line 229, in run_module
  File "<frozen runpy>", line 88, in _run_code
  File "/usr/local/lib/python3.11/site-packages/black/__main__.py", line 3, in <module>
    patched_main()
  File "src/black/__init__.py", line 1447, in patched_main
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 1128, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 1053, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 1395, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/core.py", line 754, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "src/black/__init__.py", line 470, in main
  File "/usr/local/lib/python3.11/site-packages/black/files.py", line 70, in find_project_root
    src_parents = [
                  ^
  File "/usr/local/lib/python3.11/site-packages/black/files.py", line 71, in <listcomp>
    list(path.parents) + ([path] if path.is_dir() else []) for path in path_srcs
                                    ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/pathlib.py", line 1250, in is_dir
    return S_ISDIR(self.stat().st_mode)
                   ^^^^^^^^^^^
  File "/usr/local/lib/python3.11/pathlib.py", line 1013, in stat
    return os.stat(self, follow_symlinks=follow_symlinks)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 36] File name too long: '/dev-container+7b22686f737450617468223a225c5c5c5c77736c2e6c6f63616c686f73745c5c5562756e747532342d56504e2d4b69745c5c686f6d655c5c7a3132343038395c5c6769745f77735c5c446174615f536f6c7574696f6e735f44617461627269636b73222c226c6f63616c446f636b6572223a66616c73652c22636f6e66696746696c65223a7b22246d6964223a312c2270617468223a222f686f6d652f7a3132343038392f6769745f77732f446174615f536f6c7574696f6e735f44617461627269636b732f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c22736368656d65223a227673636f64652d66696c65486f7374227d7d/workspaces/foo/bar.py'

[donverduyn]

Since this was released, there have been errors in the CI. I did check in vscode after it got merged and the prerelease did not yet include the updated package, but the stack traces themselves have regressed since then.

[ahemwe]

After weekend I got an update to 2026.6.0:

Fortunately, the bug is gone. Arguments to black don't contain the quite long /dev-container+... path any more.
Instead, it's a local path:

2026-07-06 07:47:53.171 [info] /usr/local/bin/python -m black --stdin-filename /Untitled-1.py -
2026-07-06 07:47:53.171 [info] CWD formatter: /
2026-07-06 07:47:53.173 [info] reformatted /Untitled-1.py

Issue could be closed from my point of view.

[donverduyn]

I just checked against the latest version:

2026-07-06 08:31:12.108 [info] Name: Black Formatter
2026-07-06 08:31:12.108 [info] Module: black
2026-07-06 08:31:12.108 [info] Default formatter is set to ms-python.black-formatter for workspace /workspaces/wordsearch-csp
2026-07-06 08:31:12.108 [info] Interpreter from setting black-formatter.interpreter: /opt/conda/envs/dev/bin/python
2026-07-06 08:31:12.108 [info] Interpreter from setting black-formatter.interpreter: /opt/conda/envs/dev/bin/python
2026-07-06 08:31:12.108 [info] Server run command: /opt/conda/envs/dev/bin/python /home/vscode/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/tool/lsp_server.py
2026-07-06 08:31:12.108 [info] Server CWD: /workspaces/wordsearch-csp
2026-07-06 08:31:12.108 [info] Server: Start requested.
2026-07-06 08:31:12.740 [info] CWD Server: /workspaces/wordsearch-csp
2026-07-06 08:31:12.863 [info] Settings used to run Server:
[
    {
        "cwd": "/workspaces/wordsearch-csp",
        "workspace": "file:///workspaces/wordsearch-csp",
        "args": [
            "--line-length=88",
            "--preview"
        ],
        "path": [
            "/opt/conda/envs/dev/bin/black"
        ],
        "interpreter": [
            "/opt/conda/envs/dev/bin/python"
        ],
        "importStrategy": "useBundled",
        "showNotifications": "off",
        "serverTransport": "stdio"
    }
]

2026-07-06 08:31:13.173 [info] Global settings:
{
    "cwd": "${workspaceFolder}",
    "workspace": "/vscode/vscode-server/bin/linux-arm64/4fe60c8b1cdac1c4c174f2fb180d0d758272d713",
    "args": [
        "--line-length=88",
        "--preview"
    ],
    "path": [
        "/opt/conda/envs/dev/bin/black"
    ],
    "interpreter": [
        "/opt/conda/envs/dev/bin/python"
    ],
    "importStrategy": "useBundled",
    "showNotifications": "off",
    "serverTransport": "stdio"
}

2026-07-06 08:31:13.310 [info] sys.path used to run Server:
   /home/vscode/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/libs
   /home/vscode/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/tool
   /opt/conda/envs/dev/lib/python311.zip
   /opt/conda/envs/dev/lib/python3.11
   /opt/conda/envs/dev/lib/python3.11/lib-dynload
   /opt/conda/envs/dev/lib/python3.11/site-packages
2026-07-06 08:31:13.341 [info] /opt/conda/envs/dev/bin/black --version
2026-07-06 08:31:13.467 [info] CWD Server: /workspaces/wordsearch-csp
2026-07-06 08:31:13.697 [info] Version info for formatter running for /workspaces/wordsearch-csp:
black, 26.5.1 (compiled: no)
Python (CPython) 3.11.12

2026-07-06 08:31:13.858 [info] SUPPORTED black>=22.3.0
FOUND black==26.5.1

2026-07-06 08:31:28.108 [info] Server restart triggered by: restart command
2026-07-06 08:31:28.110 [info] Interpreter from setting black-formatter.interpreter: /opt/conda/envs/dev/bin/python
2026-07-06 08:31:28.121 [info] Server: Stop requested
2026-07-06 08:31:28.121 [info] [Trace - 8:31:28 AM] Sending request 'shutdown - (1)'.
2026-07-06 08:31:28.162 [info] [Trace - 8:31:28 AM] Received response 'shutdown - (1)' in 41ms.
2026-07-06 08:31:28.163 [info] [Trace - 8:31:28 AM] Sending notification 'exit'.
2026-07-06 08:31:28.168 [info] Interpreter from setting black-formatter.interpreter: /opt/conda/envs/dev/bin/python
2026-07-06 08:31:28.234 [info] Server run command: /opt/conda/envs/dev/bin/python /home/vscode/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/tool/lsp_server.py
2026-07-06 08:31:28.234 [info] Server CWD: /workspaces/wordsearch-csp
2026-07-06 08:31:28.234 [info] Server: Start requested.
2026-07-06 08:31:30.194 [info] CWD Server: /workspaces/wordsearch-csp
2026-07-06 08:31:30.195 [info] Settings used to run Server:
[
    {
        "cwd": "/workspaces/wordsearch-csp",
        "workspace": "file:///workspaces/wordsearch-csp",
        "args": [
            "--line-length=88",
            "--preview"
        ],
        "path": [
            "/opt/conda/envs/dev/bin/black"
        ],
        "interpreter": [
            "/opt/conda/envs/dev/bin/python"
        ],
        "importStrategy": "useBundled",
        "showNotifications": "off",
        "serverTransport": "stdio"
    }
]

2026-07-06 08:31:30.195 [info] Global settings:
{
    "cwd": "${workspaceFolder}",
    "workspace": "/vscode/vscode-server/bin/linux-arm64/4fe60c8b1cdac1c4c174f2fb180d0d758272d713",
    "args": [
        "--line-length=88",
        "--preview"
    ],
    "path": [
        "/opt/conda/envs/dev/bin/black"
    ],
    "interpreter": [
        "/opt/conda/envs/dev/bin/python"
    ],
    "importStrategy": "useBundled",
    "showNotifications": "off",
    "serverTransport": "stdio"
}

2026-07-06 08:31:30.195 [info] sys.path used to run Server:
   /home/vscode/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/libs
   /home/vscode/.vscode-server/extensions/ms-python.black-formatter-2026.7.11811009/bundled/tool
   /opt/conda/envs/dev/lib/python311.zip
   /opt/conda/envs/dev/lib/python3.11
   /opt/conda/envs/dev/lib/python3.11/lib-dynload
   /opt/conda/envs/dev/lib/python3.11/site-packages
2026-07-06 08:31:30.195 [info] /opt/conda/envs/dev/bin/black --version
2026-07-06 08:31:30.195 [info] CWD Server: /workspaces/wordsearch-csp
2026-07-06 08:31:30.597 [info] Version info for formatter running for /workspaces/wordsearch-csp:
black, 26.5.1 (compiled: no)
Python (CPython) 3.11.12

2026-07-06 08:31:30.598 [info] SUPPORTED black>=22.3.0
FOUND black==26.5.1

2026-07-06 08:39:23.541 [info] [Trace - 8:39:23 AM] Sending request 'textDocument/formatting - (1)'.
2026-07-06 08:39:23.712 [info] [Trace - 8:39:23 AM] Received notification 'window/logMessage'.
2026-07-06 08:39:23.712 [info] /opt/conda/envs/dev/bin/black --line-length=88 --preview --stdin-filename //dev-container+7b22686f737450617468223a222f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d637370222c226c6f63616c446f636b6572223a66616c73652c2273657474696e6773223a7b22636f6e74657874223a226465736b746f702d6c696e7578227d2c22636f6e66696746696c65223a7b22246d6964223a312c22667350617468223a222f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d6373702f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2265787465726e616c223a2266696c653a2f2f2f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d6373702f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2270617468223a222f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d6373702f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c22736368656d65223a2266696c65227d7d/workspaces/wordsearch-csp/notebooks/wordsearch/wordsearch.py -
2026-07-06 08:39:23.712 [info] [Trace - 8:39:23 AM] Received notification 'window/logMessage'.
2026-07-06 08:39:23.712 [info] CWD Server: /workspaces/wordsearch-csp
2026-07-06 08:39:24.055 [info] [Trace - 8:39:24 AM] Received notification 'window/logMessage'.
2026-07-06 08:39:24.055 [info] Traceback (most recent call last):
  File "/opt/conda/envs/dev/bin/black", line 10, in <module>
    sys.exit(patched_main())
             ^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/black/__init__.py", line 1702, in patched_main
    main()
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/click/core.py", line 1524, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/click/core.py", line 1444, in main
    with self.make_context(prog_name, args, **extra) as ctx:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/click/core.py", line 1255, in make_context
    self.parse_args(ctx, args)
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/click/core.py", line 1266, in parse_args
    _, args = param.handle_parse_result(ctx, opts, args)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/click/core.py", line 2635, in handle_parse_result
    value = self.process_value(ctx, value)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/click/core.py", line 3436, in process_value
    return super().process_value(ctx, value)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/click/core.py", line 2497, in process_value
    value = self.callback(ctx, self, value)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/black/__init__.py", line 125, in read_pyproject_toml
    value = find_pyproject_toml(
            ^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/black/files.py", line 102, in find_pyproject_toml
    path_project_root, _ = find_project_root(path_search_start, stdin_filename)
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/black/files.py", line 74, in find_project_root
    src_parents = [
                  ^
  File "/opt/conda/envs/dev/lib/python3.11/site-packages/black/files.py", line 75, in <listcomp>
    list(path.parents) + ([path] if path.is_dir() else []) for path in path_srcs
                                    ^^^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/pathlib.py", line 1250, in is_dir
    return S_ISDIR(self.stat().st_mode)
                   ^^^^^^^^^^^
  File "/opt/conda/envs/dev/lib/python3.11/pathlib.py", line 1013, in stat
    return os.stat(self, follow_symlinks=follow_symlinks)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 36] File name too long: '/dev-container+7b22686f737450617468223a222f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d637370222c226c6f63616c446f636b6572223a66616c73652c2273657474696e6773223a7b22636f6e74657874223a226465736b746f702d6c696e7578227d2c22636f6e66696746696c65223a7b22246d6964223a312c22667350617468223a222f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d6373702f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2265787465726e616c223a2266696c653a2f2f2f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d6373702f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c2270617468223a222f55736572732f646f6e6e792f50726f6a656374732f776f72647365617263682d6373702f2e646576636f6e7461696e65722f646576636f6e7461696e65722e6a736f6e222c22736368656d65223a2266696c65227d7d/workspaces/wordsearch-csp/notebooks/wordsearch/wordsearch.py'

2026-07-06 08:39:24.056 [info] [Trace - 8:39:24 AM] Received response 'textDocument/formatting - (1)' in 515ms.
2026-07-06 08:39:24.319 [info] [Trace - 8:39:24 AM] Sending notification 'notebookDocument/didSave'.
2026-07-06 08:39:24.325 [info] Ignoring notification for unknown method 'notebookDocument/didSave'