tests: detect stale Cython .so files at test startup

[mykaul]

Add a pytest_configure hook in tests/conftest.py that compares mtime of each compiled .so against its .py source and warns when the source is newer. This prevents silently testing stale compiled code after editing a Cython-compiled module without rebuilding.
(Bit me here - #749 )

Also document the rebuild requirement in CONTRIBUTING.rst.

Pre-review checklist

• I have split my patch into logically separate commits.
• All commit messages clearly explain what they change and why.
• I added relevant tests for new features and bug fixes.
• All commits compile, pass static checks and pass test.
• PR description sums up the changes and reasons why they should be introduced.
• I have provided docstrings for the public items that I want to introduce.
• I have adjusted the documentation in ./docs/source/.
• I added appropriate Fixes: annotations to PR description.

[Copilot]

Pull request overview

Adds early test-session detection of stale in-place Cython extension builds (to avoid running tests against outdated compiled code) and documents the rebuild requirement for contributors.

Changes:

• Add pytest_configure hook in tests/conftest.py to warn when a compiled extension is older than its corresponding cassandra/*.py source.
• Document the required python setup.py build_ext --inplace rebuild step in CONTRIBUTING.rst and note that tests will warn when staleness is detected.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
tests/conftest.py	New pytest startup hook that scans for stale compiled extensions vs .py sources and emits a warning.
CONTRIBUTING.rst	Adds contributor guidance about rebuilding extensions to avoid testing stale compiled code.

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[Copilot]

Pull request overview

Adds a pytest startup check to help developers avoid accidentally running tests against stale Cython-compiled extensions when the corresponding cassandra/*.py sources have been edited without rebuilding, and documents the rebuild requirement for contributors.

Changes:

• Introduces a pytest_configure hook that scans for Cython extension modules and warns when a compiled extension appears older than its .py source.
• Documents the need to rebuild extensions after editing Cython-compiled cassandra/ modules, noting that the test suite will warn on staleness.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/conftest.py	Adds a pytest session-start hook that attempts to detect stale Cython extension artifacts and emits a warning.
CONTRIBUTING.rst	Adds contributor guidance about rebuilding extensions after modifying Cython-compiled driver modules.

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[Copilot]

Using glob('*{suffix}') while iterating importlib.machinery.EXTENSION_SUFFIXES can yield false positives because the generic suffixes (e.g. .so/.pyd) will match ABI-tagged extension files that the import system would not load for that suffix (and can also match extensions built for other Python versions, like query.cpython-310-...so). This may warn that tests will run stale compiled code even when the current interpreter would import the .py (or a different, newer extension).

Consider iterating over .py sources and, per module, selecting the first exact existing module_name + suffix in EXTENSION_SUFFIXES order (i.e., the one Python would actually import) and only comparing that file’s mtime to the .py mtime; also mark the module as processed regardless of staleness to avoid redundant checks.

Suggested change

	seen = set()
	stale = []
	# Use the current interpreter's extension suffixes so we only check
	# extensions that would actually be loaded (correct ABI tag), and
	# handle both .so (POSIX) and .pyd (Windows) automatically.
	for suffix in importlib.machinery.EXTENSION_SUFFIXES:
	for ext_path in glob.glob(os.path.join(_CASSANDRA_DIR, f"*{suffix}")):
	module_name = os.path.basename(ext_path).split(".")[0]
	if module_name in seen:
	continue
	py_path = os.path.join(_CASSANDRA_DIR, module_name + ".py")
	if os.path.exists(py_path) and os.path.getmtime(py_path) > os.path.getmtime(
	ext_path
	):
	seen.add(module_name)
	stale.append((module_name, ext_path, py_path))
	stale = []
	# Iterate over .py sources and, for each module, look for the first
	# existing compiled extension in EXTENSION_SUFFIXES order. This mirrors
	# how Python's import machinery selects an extension module, and avoids
	# globbing patterns like "*{suffix}" that can pick up ABI-tagged
	# extensions built for other Python versions.
	if os.path.isdir(_CASSANDRA_DIR):
	for entry in os.listdir(_CASSANDRA_DIR):
	if not entry.endswith(".py"):
	continue
	module_name, _ = os.path.splitext(entry)
	py_path = os.path.join(_CASSANDRA_DIR, entry)
	# For this module, find the first extension file Python would load.
	for suffix in importlib.machinery.EXTENSION_SUFFIXES:
	ext_path = os.path.join(_CASSANDRA_DIR, module_name + suffix)
	if not os.path.exists(ext_path):
	continue
	if os.path.getmtime(py_path) > os.path.getmtime(ext_path):
	stale.append((module_name, ext_path, py_path))
	# Only consider the first matching suffix; this is the one
	# the import system would actually use.
	break