mirror of
https://github.com/pre-commit/pre-commit.git
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6cd92aa910
- Add module-level docstring - Extract subprocess script into helper function - Add constant for blocked sysconf error message - Improve test docstring explaining two-phase approach - Add inline comments clarifying test orchestration - Remove TODO comments
70 lines
2.6 KiB
Python
70 lines
2.6 KiB
Python
"""Tests for pre_commit.xargs when os.sysconf is blocked in a sandbox environment."""
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from __future__ import annotations
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import subprocess
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import sys
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import textwrap
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# flake8: noqa: E501
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# Error message when os.sysconf is blocked in the test subprocess
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BLOCKED_SYSCONF_ERROR = 'blocked'
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def _create_import_test_script() -> str:
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"""Create a Python script that tests importing pre_commit.xargs with blocked os.sysconf.
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This script must run in a subprocess (not in the main pytest process) because:
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1. We need to patch os.sysconf BEFORE any imports happen
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2. conftest.py already imports pre_commit.xargs in the main process
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3. A subprocess gives us a clean import state to test against
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"""
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return textwrap.dedent(f"""
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import importlib
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import os
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from unittest import mock
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def main():
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# Force a posix-style environment.
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os.name = 'posix'
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# Block os.sysconf so that any SC_ARG_MAX lookup fails with OSError.
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with mock.patch.object(os, 'sysconf', side_effect=OSError('{BLOCKED_SYSCONF_ERROR}')):
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# This should NOT raise with the fixed implementation.
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importlib.import_module('pre_commit.xargs')
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if __name__ == '__main__':
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main()
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""")
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def test_import_module_without_throwing_exception_as_subprocess() -> None:
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"""Test that pre_commit.xargs can be imported when os.sysconf is blocked.
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This test uses a subprocess to avoid the conftest.py chicken/egg problem:
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- Phase 1 (this function): Sets up and runs a subprocess with blocked os.sysconf
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- Phase 2 (subprocess script): Attempts to import pre_commit.xargs in that environment
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With the current buggy implementation, the subprocess crashes because os.sysconf
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is called at import time. After the fix, the subprocess should succeed.
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"""
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# Create the test script that will run in a subprocess
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script = _create_import_test_script()
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# Run the script in a fresh subprocess where we control os.sysconf
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proc = subprocess.run(
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[sys.executable, '-c', script],
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capture_output=True,
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text=True,
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cwd='/Users/michael/repos/pre-commit',
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)
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# Assert the subprocess succeeded (import worked without exception)
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# Test-first: This test FAILS with current buggy behavior (subprocess crashes).
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# After fix, subprocess should succeed (returncode == 0).
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assert proc.returncode == 0, (
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f'Subprocess failed to import pre_commit.xargs when os.sysconf is blocked. '
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f'This exposes the bug: os.sysconf is called at import time. '
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f'stderr: {proc.stderr!r}'
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)
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