python-pytest-root-package-import

Answer

Root cause. pytest 9's default importlib import mode never mutates sys.path, and the pytest console script doesn't put cwd at sys.path[0]. So in a root-package repo (todo_stats/__init__.py + tests/), import todo_stats inside a test raises ModuleNotFoundError under bare pytest. python3 -m pytest works because the interpreter prepends cwd to sys.path[0] for -m runs.

Fix. At gitreins init time, probe for the layout (root package dirs + tests/ + no pytest pythonpath config) and generate python3 -m pytest -x --tb=short when it matches; keep bare pytest -x --tb=short otherwise. Also widen the guard_manager diff-narrowing regex to python3?\s+-m\s+pytest.

# gitreins/guard.py (new module) — probe + command selection + regex

GUARD_BARE       = "pytest -x --tb=short"
GUARD_VIA_MODULE = "python3 -m pytest -x --tb=short"

# Must match both bare and `python3 -m pytest`; `python3?` covers
# python/python3, `\s+` any whitespace run, `(?![\w-])` rejects identifiers
# like pytest3 / pytest-foo. Spec pattern: python3?\s+-m\s+pytest
PYTEST_GUARD_RE = re.compile(r"(?:python3?\s+-m\s+)?pytest(?![\\w-])(?:\\s+[^\\n]*)?")

_PYTHONPATH_ASSIGN = re.compile(r"^[ \t]*pythonpath[ \t]*=", re.MULTILINE)
_INI_FILES = ("pytest.ini", "setup.cfg", "tox.ini")
_SKIP_DIRS = frozenset({"tests", "test", "src"})

def _toml_has_pythonpath(root):            # pyproject.toml, [tool.pytest.ini_options]
    text = (root / "pyproject.toml").read_text(encoding="utf-8", errors="replace")
    return "[tool.pytest.ini_options]" in text and bool(_PYTHONPATH_ASSIGN.search(text))

def _ini_has_pythonpath(root, name):       # pytest.ini / setup.cfg / tox.ini
    parser = configparser.ConfigParser()
    try:
        parser.read(root / name, encoding="utf-8")
    except (configparser.Error, UnicodeDecodeError, OSError):   # unparseable → raw scan
        try: text = (root / name).read_text(encoding="utf-8", errors="replace")
        except OSError: return False
        return bool(_PYTHONPATH_ASSIGN.search(text))
    return any(parser.has_option(s, "pythonpath") for s in ("pytest", "tool:pytest"))

def probe_root_package(root):
    """True → bare `pytest` cannot import the package; must use `python3 -m pytest`."""
    if not (root / "tests").is_dir():
        return False
    has_root_package = any(
        child.is_dir()
        and not child.name.startswith(".")
        and child.name not in _SKIP_DIRS
        and (child / "__init__.py").is_file()
        for child in root.iterdir()
    )
    if not has_root_package:
        return False
    if (root / "pyproject.toml").is_file() and _toml_has_pythonpath(root):
        return False
    return not any((root / n).is_file() and _ini_has_pythonpath(root, n) for n in _INI_FILES)

def pytest_guard_command(root):
    """Called by `gitreins init` when writing the guard for a fresh repo."""
    return GUARD_VIA_MODULE if probe_root_package(root) else GUARD_BARE

def narrow_pytest_guard(diff_text):
    """Called by guard_manager to locate the pytest invocation in a diff."""
    m = PYTEST_GUARD_RE.search(diff_text)
    return m.group(0) if m else None

Integration points (in gitreins): - gitreins init: replace the hardcoded pytest -x --tb=short with pytest_guard_command(root). - guard_manager: use PYTEST_GUARD_RE (or narrow_pytest_guard) when narrowing guard diffs, so both pytest … and python3 -m pytest … invocations are recognized.

Why the probe's three conditions are exactly right: (1) tests/ proves tests import the package; (2) a root-level dir with __init__.py (excluding tests/, test/, src/, dot-dirs) is what -m makes importable — a src/-layout package is not importable by -m either, so the bare guard stays there; (3) any pythonpath config (pyproject.toml, pytest.ini, setup.cfg, tox.ini) makes bare pytest work, so the probe must be False to keep the shorter command.