File "/Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/vscode_pytest/__init__.py", line 25, in <module>
from typing_extensions import NotRequired
ImportError: Error importing plugin "vscode_pytest": No module named 'typing_extensions'
Important note: Once I switched from "Pre-release version" to released version, the problem disappeared. This means that the attached extension issue you see here is not the same as the extension version I was using when I encountered the problem. Sorry about that.
Note that I cannot reproduce this at the moment. I will need to try again with the pre-release.
Initially, I believed that I had made a configuration error with workspaces and this mono-repo. (This later turned out not to be the case as I checked a project that had previously beeen workinghttps://github.com/jpgoldberg/toy-crypto-math just fine a couple of days ago), but I still considered the error peculiar for a configuratin error. None the less, I attemped various things from manually checking that typing-extensions was installed in the environment, to switching Python interprerters, fully quitting and restarting VSCode.
Most usefully for you is that I repeated all of the queries and checks outlined in issue #24414, including the attempt to use unittest instead of pytest and confirmed that the extension was in place.
pytest on the command line was working for me, as was "Debug Current File" on a test file.
2025-11-20 18:29:30.108 [info] Native locator: Refresh started
2025-11-20 18:29:30.108 [info] Pyenv environment manager found at: /opt/homebrew/bin/pyenv
2025-11-20 18:29:30.108 [info] VS Code was launched from an activated environment: '.venv', selecting it as the interpreter for workspace.
2025-11-20 18:29:30.108 [info] Active interpreter [/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades]: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/bin/python
2025-11-20 18:29:30.108 [info] > /opt/homebrew/bin/pyenv which python
2025-11-20 18:29:30.108 [info] cwd: .
2025-11-20 18:29:30.133 [info] Python interpreter path: ./.venv/bin/python
2025-11-20 18:29:31.000 [info] Native locator: Refresh finished in 1078 ms
2025-11-20 18:29:32.442 [info] Starting Pylance language server.
2025-11-20 18:29:54.019 [info] Native locator: Refresh started
2025-11-20 18:29:54.032 [info] Pyenv environment manager found at: /opt/homebrew/bin/pyenv
2025-11-20 18:29:54.048 [info] Native locator: Refresh started
2025-11-20 18:29:54.062 [info] VS Code was launched from an activated environment: '.venv', selecting it as the interpreter for workspace.
2025-11-20 18:29:54.129 [info] Active interpreter [/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades]: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/bin/python
2025-11-20 18:29:54.134 [info] > /opt/homebrew/bin/pyenv which python
2025-11-20 18:29:54.134 [info] cwd: .
2025-11-20 18:29:54.675 [info] Native locator: Refresh finished in 733 ms
2025-11-20 18:29:54.715 [info] Python interpreter path: ./.venv/bin/python
2025-11-20 18:29:56.082 [info] Starting Pylance language server.
2025-11-20 18:30:05.465 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:30:05.470 [info] Environment variables set for pytest discovery: PYTHONPATH=/Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files, TEST_RUN_PIPE=/var/folders/tm/cypvg3691_b5mh6kj15wlft40000gn/T/python-test-discovery-41130c696a513fe56355
2025-11-20 18:30:05.473 [info] > . ./.venv/bin/activate && echo 'e8b39361-0157-4923-80e1-22d70d46dee6' && python ~/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/printEnvVariables.py
2025-11-20 18:30:05.474 [info] shell: bash
2025-11-20 18:30:05.505 [info] > ./.venv/bin/python -m pytest -p vscode_pytest --collect-only tests --rootdir=.
2025-11-20 18:30:05.506 [info] cwd: .
2025-11-20 18:30:05.635 [error] Traceback (most recent call last):
2025-11-20 18:30:05.635 [error] File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 876, in import_plugin
__import__(importspec)
~~~~~~~~~~^^^^^^^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/assertion/rewrite.py", line 197, in exec_module
exec(co, module.__dict__)
~~~~^^^^^^^^^^^^^^^^^^^^^
File "/Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/vscode_pytest/__init__.py", line 25, in <module>
from typing_extensions import NotRequired
2025-11-20 18:30:05.635 [error] ModuleNotFoundError: No module named 'typing_extensions'
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
2025-11-20 18:30:05.636 [error] File "<frozen runpy>", line 198, in _run_module_as_main
File "<frozen runpy>", line 88, in _run_code
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/pytest/__main__.py", line 9, in <module>
raise SystemExit(pytest.console_main())
~~~~~~~~~~~~~~~~~~~^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 221, in console_main
code = main()
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 191, in main
config = _prepareconfig(new_args, plugins)
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 358, in _prepareconfig
config: Config = pluginmanager.hook.pytest_cmdline_parse(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
pluginmanager=pluginmanager, args=args
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/pluggy/_hooks.py", line 512, in __call__
return self._hookexec(self.name, self._hookimpls.copy(), kwargs, firstresult)
~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/pluggy/_manager.py", line 120, in _hookexec
return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/pluggy/_callers.py", line 167, in _multicall
raise exception
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/pluggy/_callers.py", line 139, in _multicall
teardown.throw(exception)
~~~~~~~~~~~~~~^^^^^^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/helpconfig.py", line 124, in pytest_cmdline_parse
config = yield
^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/pluggy/_callers.py", line 121, in _multicall
res = hook_impl.function(*args)
2025-11-20 18:30:05.636 [error] File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 1155, in pytest_cmdline_parse
self.parse(args)
~~~~~~~~~~^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 1501, in parse
self.pluginmanager.consider_preparse(args, exclude_only=False)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 805, in consider_preparse
self.consider_pluginarg(parg)
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 828, in consider_pluginarg
self.import_plugin(arg, consider_entry_points=True)
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 878, in import_plugin
raise ImportError(
f'Error importing plugin "{modname}": {e.args[0]}'
).with_traceback(e.__traceback__) from e
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/config/__init__.py", line 876, in import_plugin
__import__(importspec)
~~~~~~~~~~^^^^^^^^^^^^
File "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/lib/python3.13/site-packages/_pytest/assertion/rewrite.py", line 197, in exec_module
exec(co, module.__dict__)
~~~~^^^^^^^^^^^^^^^^^^^^^
File "/Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/vscode_pytest/__init__.py", line 25, in <module>
from typing_extensions import NotRequired
ImportError: Error importing plugin "vscode_pytest": No module named 'typing_extensions'
2025-11-20 18:30:05.649 [error] Subprocess exited unsuccessfully with exit code 1 and signal null on workspace /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades.
2025-11-20 18:30:05.649 [error] Subprocess exited unsuccessfully with exit code 1 and signal null on workspace /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades. Creating and sending error discovery payload
2025-11-20 18:30:05.649 [error] pytest test discovery error for workspace: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
The python test process was terminated before it could exit on its own, the process errored with: Code: 1, Signal: null for workspace /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:33:02.295 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.vscode/settings.json
2025-11-20 18:33:02.296 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:33:03.009 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:33:03.009 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:35:04.086 [info] > conda info --json
2025-11-20 18:35:38.539 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/tests/test_unittest.py
2025-11-20 18:35:38.540 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:36:02.010 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/tests/test_unittest.py
2025-11-20 18:36:02.010 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:36:47.844 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/tests/test_unittest.py
2025-11-20 18:36:47.844 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:36:58.082 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/tests/test_unittest.py
2025-11-20 18:36:58.082 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:39:31.826 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:39:31.826 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:39:51.799 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.vscode/settings.json
2025-11-20 18:39:51.800 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:39:52.317 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:39:52.317 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:40:51.162 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.vscode/settings.json
2025-11-20 18:40:51.162 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:40:51.883 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:40:51.883 [error] Test provider in adapter is not unittest. Please reload window.
2025-11-20 18:44:36.054 [info] Native locator: Refresh started
2025-11-20 18:44:36.066 [info] Native locator: Refresh started
2025-11-20 18:44:36.075 [info] > conda info --json
2025-11-20 18:44:36.079 [info] VS Code was launched from an activated environment: '.venv', selecting it as the interpreter for workspace.
2025-11-20 18:44:36.209 [info] > pyenv which python
2025-11-20 18:44:36.209 [info] cwd: .
2025-11-20 18:44:36.235 [info] Pyenv environment manager found at: /opt/homebrew/bin/pyenv
2025-11-20 18:44:36.965 [info] Python interpreter path: ./.venv/bin/python
2025-11-20 18:44:37.041 [info] Native locator: Refresh finished in 1220 ms
2025-11-20 18:44:38.301 [info] Starting Pylance language server.
2025-11-20 18:45:15.865 [info] Native locator: Refresh started
2025-11-20 18:45:15.877 [info] Native locator: Refresh started
2025-11-20 18:45:15.885 [info] > conda info --json
2025-11-20 18:45:15.889 [info] VS Code was launched from an activated environment: '.venv', selecting it as the interpreter for workspace.
2025-11-20 18:45:16.030 [info] > pyenv which python
2025-11-20 18:45:16.030 [info] cwd: .
2025-11-20 18:45:16.041 [info] Pyenv environment manager found at: /opt/homebrew/bin/pyenv
2025-11-20 18:45:16.764 [info] Python interpreter path: ./.venv/bin/python
2025-11-20 18:45:16.861 [info] Native locator: Refresh finished in 1234 ms
2025-11-20 18:45:17.955 [info] Starting Pylance language server.
2025-11-20 18:46:09.726 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:46:09.732 [info] Discovering unittest tests for workspace /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades with arguments: /Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/discovery.py,--udiscovery,-v,-s,./tests,-p,test_*.py
2025-11-20 18:46:09.737 [info] > . ./.venv/bin/activate && echo 'e8b39361-0157-4923-80e1-22d70d46dee6' && python ~/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/printEnvVariables.py
2025-11-20 18:46:09.737 [info] shell: bash
2025-11-20 18:46:09.775 [info] > ./.venv/bin/python ~/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/discovery.py --udiscovery -v -s ./tests -p test_*.py
2025-11-20 18:46:09.775 [info] cwd: .
2025-11-20 18:47:42.634 [info] Running UNITTEST execution for the following test ids: test_grades.TestDefault.test_abnormal,test_grades.TestDefault.test_exceptions,test_grades.TestDefault.test_init,test_grades.TestDefault.test_normal
2025-11-20 18:47:42.634 [info] Attempting to use temp directory for test ids file, file name: test-ids-d6ba19cb287c500df132.txt
2025-11-20 18:47:42.635 [info] All environment variables set for unittest execution, PYTHONPATH: "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades"
2025-11-20 18:47:42.636 [info] Running unittests for workspace /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades with arguments: /Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/execution.py,--udiscovery,-v,-s,./tests,-p,test_*.py
2025-11-20 18:47:42.636 [info] > ./.venv/bin/python ~/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/execution.py --udiscovery -v -s ./tests -p test_*.py
2025-11-20 18:47:42.636 [info] cwd: .
2025-11-20 18:47:42.790 [info] Test Result named pipe /var/folders/tm/cypvg3691_b5mh6kj15wlft40000gn/T/python-test-results-dab1d69df3e2c962db7c cancelled
2025-11-20 18:48:08.137 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:48:08.141 [info] Discovering unittest tests for workspace /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades with arguments: /Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/discovery.py,--udiscovery,-v,-s,./tests,-p,test_*.py
2025-11-20 18:48:08.142 [info] > ./.venv/bin/python ~/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/discovery.py --udiscovery -v -s ./tests -p test_*.py
2025-11-20 18:48:08.142 [info] cwd: .
2025-11-20 18:48:11.846 [info] > . ./.venv/bin/activate && echo 'e8b39361-0157-4923-80e1-22d70d46dee6' && python ~/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/printEnvVariables.py
2025-11-20 18:48:11.846 [info] shell: bash
2025-11-20 18:48:11.878 [info] > ./.venv/bin/python -c "import pytest"
2025-11-20 18:48:12.348 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.vscode/settings.json
2025-11-20 18:48:12.348 [error] Test provider in adapter is not pytest. Please reload window.
2025-11-20 18:48:12.864 [info] Discover tests for workspace name: grades - uri: /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades
2025-11-20 18:48:12.865 [error] Test provider in adapter is not pytest. Please reload window.
2025-11-20 18:48:23.639 [info] Running UNITTEST execution for the following test ids: test_grades.TestDefault.test_abnormal,test_grades.TestDefault.test_exceptions,test_grades.TestDefault.test_init,test_grades.TestDefault.test_normal,test_grades.TestGrader.test_duplicate_grades,test_grades.TestGrader.test_min_mismatch
2025-11-20 18:48:23.639 [info] Attempting to use temp directory for test ids file, file name: test-ids-9e09af14ecb27e033c2c.txt
2025-11-20 18:48:23.641 [info] All environment variables set for unittest execution, PYTHONPATH: "/Users/jeffrey/src/github.com/jpgoldberg/pointless/grades"
2025-11-20 18:48:23.642 [info] Running unittests for workspace /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades with arguments: /Users/jeffrey/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/execution.py,--udiscovery,-v,-s,./tests,-p,test_*.py
2025-11-20 18:48:23.642 [info] > ./.venv/bin/python ~/.vscode/extensions/ms-python.python-2025.19.2025111801-darwin-arm64/python_files/unittestadapter/execution.py --udiscovery -v -s ./tests -p test_*.py
2025-11-20 18:48:23.642 [info] cwd: .
2025-11-20 18:48:23.785 [info] Test Result named pipe /var/folders/tm/cypvg3691_b5mh6kj15wlft40000gn/T/python-test-results-0583009a3ca93f18f981 cancelled
2025-11-20 18:49:30.543 [info] Send text to terminal: source /Users/jeffrey/src/github.com/jpgoldberg/pointless/grades/.venv/bin/activate
Type: Bug
Behaviour
The behavior is similar to what was reported in issue 24414
(I will attempt to attache the full log)
Important note: Once I switched from "Pre-release version" to released version, the problem disappeared. This means that the attached extension issue you see here is not the same as the extension version I was using when I encountered the problem. Sorry about that.
I was using pytest, but I also tested with unittest test suggested in #24414 (comment)
During test discovery, I was
Steps to reproduce:
Note that I cannot reproduce this at the moment. I will need to try again with the pre-release.
Things I tried
Initially, I believed that I had made a configuration error with workspaces and this mono-repo. (This later turned out not to be the case as I checked a project that had previously beeen workinghttps://github.com/jpgoldberg/toy-crypto-math just fine a couple of days ago), but I still considered the error peculiar for a configuratin error. None the less, I attemped various things from manually checking that typing-extensions was installed in the environment, to switching Python interprerters, fully quitting and restarting VSCode.
Most usefully for you is that I repeated all of the queries and checks outlined in issue #24414, including the attempt to use unittest instead of pytest and confirmed that the extension was in place.
pytest on the command line was working for me, as was "Debug Current File" on a test file.
Diagnostic data
Python.log. Time stamps are US Central time. It is before 18:45 when I switched to release version of extensions.Extension version: 2025.19.2025111801
VS Code version: Code 1.106.2 (Universal) (1e3c50d64110be466c0b4a45222e81d2c9352888, 2025-11-19T16:56:50.023Z)
OS version: Darwin arm64 25.1.0
Modes:
python.languageServersetting: DefaultUser Settings
Installed Extensions
System Info
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
A/B Experiments