python: propagate package-level pytestmark from __init__.py

[aryansk]

Problem

A pytestmark = pytest.mark.skip(...) (or xfail, etc.) defined in a package's __init__.py no longer propagates to tests inside that package. Tests that should be skipped run and fail instead.

Minimal reproduction from #14737:

from pathlib import Path
import pytest
root = Path("/tmp/pytest_pkg_skip_test")
package = root / "skippedpkg"
package.mkdir(parents=True)
(package / "__init__.py").write_text("import pytest\npytestmark = pytest.mark.skip(reason='package is disabled')\n")
(package / "test_skipped.py").write_text("def test_should_be_skipped():\n    assert False\n")
pytest.main(["-q", str(package)])  # expected 1 skipped, got 1 failed

This is a consequence of #6197. Before #6197, Package was a Module and its __init__.py was loaded via PyobjMixin.obj which populated own_markers via get_unpacked_marks. #6197 made Package a Directory to fix incorrect discovery of non-test __init__.py files (#6194) and removed that marking path, without replacement.

Fixes #14737.

Change

In src/_pytest/python.py Package.collect, import the package's __init__.py via importtestmodule (already used in Package.setup for setup_module), extract marks with get_unpacked_marks, and extend self.own_markers / self.keywords before yielding children. Children inherit via Node.iter_markers_with_node.

• Do it in collect (not setup) so marks are visible during collection and before pytest_runtest_setup (the skipping plugin is tryfirst, while Package.setup runs after).
• Snapshot and restore sys.modules / sys.path when no marks are applied to avoid polluting unrelated imports (e.g. src/nope in test_does_not_put_src_on_path). When marks are applied we keep the import so Package.setup does not need to re-execute __init__.py.
• Guard against double-collect with _pytestmark_applied.

No new collection of __init__.py as a test file, so #6194 is not reintroduced.

Why this approach

• Restores the pre-Fix incorrect discovery of non-test __init__.py files. #6197 expectation (package-level marks propagate) without re-collecting __init__.py.
• Mirrors how PyobjMixin and FunctionDefinition handle pytestmark (via get_unpacked_marks → own_markers / keywords).
• setup is too late for skip/xfail evaluation; collect is the earliest point where the Package node exists and its children will inherit.

Testing

Reproduction after fix:

$ pytest -q /tmp/pytest_pkg_skip_test/skippedpkg -v
skippedpkg/test_skipped.py s [100%]
1 skipped in 0.01s   # was 1 failed

Nested package (outer skip propagates to subpackage): 2 skipped — pass.
xfail in __init__.py: 1 xfailed — pass.
Empty package: 1 passed — pass.
src/nope pollution case: 1 passed — pass (no ImportError regression).
Pre-existing regression test_skip_package scenario (root __init__.py with pytestmark = skip): 2 skipped — pass.

Repository checks:

$ pytest testing/test_mark.py -q
118 passed, 1 xfailed

$ pytest testing/python/collect.py -q
84 passed

$ pytest testing/test_collection.py -q
113 passed, 3 skipped, 1 xfailed  # test_does_not_put_src_on_path now passes

$ pytest testing/test_skipping.py -q
95 passed

Documentation and release impact

• No documentation impact
• Changelog entry needed (will add changelog/14737.bugfix.rst if requested)
• No migration note

Review notes

• Known limitations: __init__.py is imported to read marks; if it has side effects, it will be executed once during collection for packages with marks (kept), twice (collect + setup) for packages without marks that are deleted/restored. For pure-mark files this is harmless.
• Follow-up: if maintainers prefer a different layer (e.g. pytest_collection_modifyitems), happy to move the logic there.
• Security/licensing: MIT, no new dependencies.