No such file or directory: 'flake8'

[jedie]

Darker didn't find flake8... It's installed in .venv, but raised this error:

DEBUG:darkgraylib.git:[~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package]$ git rev-parse --show-toplevel
DEBUG:darkgraylib.git:[~/cookiecutter_templates]$ git worktree add --quiet --force --force /tmp/tmp3z1cls2w/baseline-revision/cookiecutter_templates origin/main
DEBUG:darkgraylib.git:[~/cookiecutter_templates]$ git rev-parse origin/main
DEBUG:graylint.linting:[/tmp/tmp3z1cls2w/baseline-revision/cookiecutter_templates]$ flake8
Traceback (most recent call last):
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/bin/darker", line 8, in <module>
    sys.exit(main_with_error_handling())
             ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/lib/python3.12/site-packages/darker/__main__.py", line 633, in main_with_error_handling
    return main()
           ^^^^^^
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/lib/python3.12/site-packages/darker/__main__.py", line 614, in main
    linter_failures_on_modified_lines = run_linters(
                                        ^^^^^^^^^^^^
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/lib/python3.12/site-packages/graylint/linting.py", line 434, in run_linters
    baseline = _get_messages_from_linters_for_baseline(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/lib/python3.12/site-packages/graylint/linting.py", line 573, in _get_messages_from_linters_for_baseline
    result = _get_messages_from_linters(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/lib/python3.12/site-packages/graylint/linting.py", line 484, in _get_messages_from_linters
    for message_location, message in run_linter(cmdline, root, paths, env).items():
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/lib/python3.12/site-packages/graylint/linting.py", line 361, in run_linter
    with _check_linter_output(cmdline, root, paths, env) as linter_stdout:
  File "/usr/lib/python3.12/contextlib.py", line 137, in __enter__
    return next(self.gen)
           ^^^^^^^^^^^^^^
  File "~/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/lib/python3.12/site-packages/graylint/linting.py", line 322, in _check_linter_output
    with Popen(  # nosec
         ^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/subprocess.py", line 1026, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.12/subprocess.py", line 1955, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'flake8'

...

~/repos/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package$ .venv/bin/flake8 --version
7.1.1 (flake8-bugbear: 24.10.31, mccabe: 0.7.0, pycodestyle: 2.12.1, pyflakes: 3.2.0) CPython 3.12.3 on Linux

Version info:

.venv/bin/uv pip freeze
...
darker==2.1.1
...
flake8==7.1.1
flake8-bugbear==24.10.31
flynt==1.0.1
graylint==1.1.1
...
pip==24.3.1
...
uv==0.5.1
...

I add a pp(locales()) into graylint.linting._check_linter_output() just before the Popen() call, looks like:

{'cmdline': 'flake8',
 'root': PosixPath('/tmp/tmpunxe_xsq/baseline-revision/cookiecutter_templates'),
 'paths': {PosixPath('generated_templates/make-uv-python/your_cool_package/.venv/bin')},
 'env': {'SHELL': '/bin/bash',
        ...
         'PWD': '/home/jens/repos/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/bin',
        ...
         'PATH': '/home/jens/.local/bin:/home/jens/.local/bin:/home/jens/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin',
        ...
         'OLDPWD': '/home/jens/repos/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package',
         '_': './darker',
         'GRAYLINT_ORIG_REPO': '/home/jens/repos/cookiecutter_templates',
         'GRAYLINT_REV_COMMIT': 'ff48b81'},
 'cmdline_parts': ['flake8'],
 'existing_path_strs': [],
 'cmdline_and_paths': ['flake8']}

[akaihola]

Hi @jedie, thanks for the report!

I didn't yet succeed to reproduce, could you advise?

uv venv
. .venv/bin/activate
uv pip install darker==2.1.1 flake8==7.1.1
darker --diff --lint=flake8 ~/mypackage/src

The above commands succeed, and these packages are installed in .venv:

$ uv pip freeze
...
darker==2.1.1
...
flake8==7.1.1
graylint==1.1.1
...

I also tried

• without activating the virtualenv and running .venv/bin/darker instead
• using python -m venv .venv and .venv/bin/pip install uv, and then using .venv/bin/uv instead of my global uv instance.

Still succeeds in both cases.

[akaihola]

Looking at items from your pp(locals()) output:

{'root': PosixPath('/tmp/tmpunxe_xsq/baseline-revision/cookiecutter_templates'),
 'paths': {PosixPath('generated_templates/make-uv-python/your_cool_package/.venv/bin')},

it seems the only .py files Darker has found are in your .../.venv/bin directory.

 'env': {
     'PWD': '/home/jens/repos/cookiecutter_templates/generated_templates/make-uv-python/your_cool_package/.venv/bin',

Graylint likes to cd into the deepest common parent directory of found .py files, so .../.venv/bin in this case...

     'PATH': '/home/jens/.local/bin:/home/jens/.local/bin:/home/jens/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin',

...and for some reason your that .../.venv/bin directory of your virtualenv has disappeared from the system path.

Do you get the same behavior if you

• run graylint --lint=flake8 (or whatever your original Darker command line was) directly, or
• run Darker in a real project repository with .py files also outside .venv, or
• place .venv outside your project repository instead?