cwd on sys.path mask stdlib modules

[jaraco]

While experimenting with adding distutils to the coherent system, I ran into an ImportError.

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/pytest/__main__.py", line 9, in <module>
    raise SystemExit(pytest.console_main())
                     ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/_pytest/config/__init__.py", line 201, in console_main
    code = main()
           ^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/_pytest/config/__init__.py", line 156, in main
    config = _prepareconfig(args, plugins)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/_pytest/config/__init__.py", line 341, in _prepareconfig
    config = pluginmanager.hook.pytest_cmdline_parse(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/pluggy/_hooks.py", line 513, in __call__
    return self._hookexec(self.name, self._hookimpls.copy(), kwargs, firstresult)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/pluggy/_manager.py", line 120, in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/pluggy/_callers.py", line 139, in _multicall
    raise exception.with_traceback(exception.__traceback__)
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/pluggy/_callers.py", line 122, in _multicall
    teardown.throw(exception)  # type: ignore[union-attr]
    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/_pytest/helpconfig.py", line 105, in pytest_cmdline_parse
    config = yield
             ^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/pluggy/_callers.py", line 103, in _multicall
    res = hook_impl.function(*args)
          ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/_pytest/config/__init__.py", line 1140, in pytest_cmdline_parse
    self.parse(args)
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/_pytest/config/__init__.py", line 1490, in parse
    self._preparse(args, addopts=addopts)
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/_pytest/config/__init__.py", line 1377, in _preparse
    self.pluginmanager.load_setuptools_entrypoints("pytest11")
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/pluggy/_manager.py", line 421, in load_setuptools_entrypoints
    plugin = ep.load()
             ^^^^^^^^^
  File "/opt/homebrew/Cellar/[email protected]/3.12.5/Frameworks/Python.framework/Versions/3.12/lib/python3.12/importlib/metadata/__init__.py", line 205, in load
    module = import_module(match.group('module'))
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/[email protected]/3.12.5/Frameworks/Python.framework/Versions/3.12/lib/python3.12/importlib/__init__.py", line 90, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1387, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1360, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1331, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 935, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 995, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/coherent/test/monkey.py", line 8, in <module>
    from coherent.build import discovery
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/coherent/build/__init__.py", line 17, in <module>
    from .backend import (
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/coherent/build/backend.py", line 20, in <module>
    from .metadata import Message
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/coherent/build/metadata.py", line 17, in <module>
    from . import discovery
  File "/Users/jaraco/Library/Application Support/pipx/venvs/coherent-cli/lib/python3.12/site-packages/coherent/build/discovery.py", line 17, in <module>
    import packaging.requirements
  File "/Users/jaraco/.local/pip-run/packaging/requirements.py", line 8, in <module>
    from ._parser import parse_requirement as _parse_requirement
  File "/Users/jaraco/.local/pip-run/packaging/_parser.py", line 12, in <module>
    from ._tokenizer import DEFAULT_RULES, Tokenizer
  File "/Users/jaraco/.local/pip-run/packaging/_tokenizer.py", line 8, in <module>
    from .specifiers import Specifier
  File "/Users/jaraco/.local/pip-run/packaging/specifiers.py", line 18, in <module>
    from .utils import canonicalize_version
  File "/Users/jaraco/.local/pip-run/packaging/utils.py", line 10, in <module>
    from .tags import Tag, parse_tag
  File "/Users/jaraco/.local/pip-run/packaging/tags.py", line 13, in <module>
    import sysconfig
  File "/Users/jaraco/code/pypa/distutils/sysconfig.py", line 19, in <module>
    from ._functools import pass_none
ImportError: attempted relative import with no known parent package

Because distutils exposes a sysconfig module and because that name masks one in the stdlib, it causes problems. Probably the test runner should make sure . isn't on sys.path.

[jaraco]

On Python 3.11 and later, -P/PYTHONSAFEPATH can be used. On older Pythons, probably a sitecustomize or some other more involved intervention would be required.