conftest.py

# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt

"""
Pytest auto configuration.

This module is run automatically by pytest, to define and enable fixtures.
"""

from __future__ import annotations

import os
import sys
import sysconfig
import warnings

from pathlib import Path
from typing import Iterator, Optional

import pytest

from coverage import env
from coverage.files import set_relative_directory

# Pytest will rewrite assertions in test modules, but not elsewhere.
# This tells pytest to also rewrite assertions in coveragetest.py.
pytest.register_assert_rewrite("tests.coveragetest")
pytest.register_assert_rewrite("tests.helpers")

# Pytest can take additional options:
# $set_env.py: PYTEST_ADDOPTS - Extra arguments to pytest.

pytest_plugins = "tests.balance_xdist_plugin"


@pytest.fixture(autouse=True)
def set_warnings() -> None:
    """Configure warnings to show while running tests."""
    warnings.simplefilter("default")
    warnings.simplefilter("once", DeprecationWarning)

    # Warnings to suppress:
    # How come these warnings are successfully suppressed here, but not in setup.cfg??

    warnings.filterwarnings(
        "ignore",
        category=DeprecationWarning,
        message=r".*imp module is deprecated in favour of importlib",
    )

    warnings.filterwarnings(
        "ignore",
        category=DeprecationWarning,
        message=r"module 'sre_constants' is deprecated",
    )

    warnings.filterwarnings(
        "ignore",
        category=pytest.PytestRemovedIn8Warning,
    )

    if env.PYPY:
        # pypy3 warns about unclosed files a lot.
        warnings.filterwarnings("ignore", r".*unclosed file", category=ResourceWarning)


@pytest.fixture(autouse=True)
def reset_sys_path() -> Iterator[None]:
    """Clean up sys.path changes around every test."""
    sys_path = list(sys.path)
    yield
    sys.path[:] = sys_path


@pytest.fixture(autouse=True)
def reset_environment() -> Iterator[None]:
    """Make sure a test setting an envvar doesn't leak into another test."""
    old_environ = os.environ.copy()
    yield
    os.environ.clear()
    os.environ.update(old_environ)


@pytest.fixture(autouse=True)
def reset_filesdotpy_globals() -> Iterator[None]:
    """coverage/files.py has some unfortunate globals. Reset them every test."""
    set_relative_directory()
    yield

WORKER = os.environ.get("PYTEST_XDIST_WORKER", "none")

def pytest_sessionstart() -> None:
    """Run once at the start of the test session."""
    # Only in the main process...
    if WORKER == "none":
        # Create a .pth file for measuring subprocess coverage.
        pth_dir = find_writable_pth_directory()
        assert pth_dir
        (pth_dir / "subcover.pth").write_text("import coverage; coverage.process_startup()\n")
        # subcover.pth is deleted by pytest_sessionfinish below.


def pytest_sessionfinish() -> None:
    """Hook the end of a test session, to clean up."""
    # This is called by each of the workers and by the main process.
    if WORKER == "none":
        for pth_dir in possible_pth_dirs():             # pragma: part covered
            pth_file = pth_dir / "subcover.pth"
            if pth_file.exists():
                pth_file.unlink()


def possible_pth_dirs() -> Iterator[Path]:
    """Produce a sequence of directories for trying to write .pth files."""
    # First look through sys.path, and if we find a .pth file, then it's a good
    # place to put ours.
    for pth_dir in map(Path, sys.path):             # pragma: part covered
        pth_files = list(pth_dir.glob("*.pth"))
        if pth_files:
            yield pth_dir

    # If we're still looking, then try the Python library directory.
    # https://github.com/nedbat/coveragepy/issues/339
    yield Path(sysconfig.get_path("purelib"))       # pragma: cant happen


def find_writable_pth_directory() -> Optional[Path]:
    """Find a place to write a .pth file."""
    for pth_dir in possible_pth_dirs():             # pragma: part covered
        try_it = pth_dir / f"touch_{WORKER}.it"
        try:
            try_it.write_text("foo")
        except OSError:                             # pragma: cant happen
            continue

        os.remove(try_it)
        return pth_dir

    return None                                     # pragma: cant happen