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Diffstat (limited to 'Lib/test/support/warnings_helper.py')
| -rw-r--r-- | Lib/test/support/warnings_helper.py | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/Lib/test/support/warnings_helper.py b/Lib/test/support/warnings_helper.py new file mode 100644 index 0000000..a024fbe --- /dev/null +++ b/Lib/test/support/warnings_helper.py @@ -0,0 +1,199 @@ +import contextlib +import functools +import re +import sys +import warnings + + +def check_syntax_warning(testcase, statement, errtext='', + *, lineno=1, offset=None): + # Test also that a warning is emitted only once. + from test.support import check_syntax_error + with warnings.catch_warnings(record=True) as warns: + warnings.simplefilter('always', SyntaxWarning) + compile(statement, '<testcase>', 'exec') + testcase.assertEqual(len(warns), 1, warns) + + warn, = warns + testcase.assertTrue(issubclass(warn.category, SyntaxWarning), + warn.category) + if errtext: + testcase.assertRegex(str(warn.message), errtext) + testcase.assertEqual(warn.filename, '<testcase>') + testcase.assertIsNotNone(warn.lineno) + if lineno is not None: + testcase.assertEqual(warn.lineno, lineno) + + # SyntaxWarning should be converted to SyntaxError when raised, + # since the latter contains more information and provides better + # error report. + with warnings.catch_warnings(record=True) as warns: + warnings.simplefilter('error', SyntaxWarning) + check_syntax_error(testcase, statement, errtext, + lineno=lineno, offset=offset) + # No warnings are leaked when a SyntaxError is raised. + testcase.assertEqual(warns, []) + + +def ignore_warnings(*, category): + """Decorator to suppress deprecation warnings. + + Use of context managers to hide warnings make diffs + more noisy and tools like 'git blame' less useful. + """ + def decorator(test): + @functools.wraps(test) + def wrapper(self, *args, **kwargs): + with warnings.catch_warnings(): + warnings.simplefilter('ignore', category=category) + return test(self, *args, **kwargs) + return wrapper + return decorator + + +class WarningsRecorder(object): + """Convenience wrapper for the warnings list returned on + entry to the warnings.catch_warnings() context manager. + """ + def __init__(self, warnings_list): + self._warnings = warnings_list + self._last = 0 + + def __getattr__(self, attr): + if len(self._warnings) > self._last: + return getattr(self._warnings[-1], attr) + elif attr in warnings.WarningMessage._WARNING_DETAILS: + return None + raise AttributeError("%r has no attribute %r" % (self, attr)) + + @property + def warnings(self): + return self._warnings[self._last:] + + def reset(self): + self._last = len(self._warnings) + + +@contextlib.contextmanager +def check_warnings(*filters, **kwargs): + """Context manager to silence warnings. + + Accept 2-tuples as positional arguments: + ("message regexp", WarningCategory) + + Optional argument: + - if 'quiet' is True, it does not fail if a filter catches nothing + (default True without argument, + default False if some filters are defined) + + Without argument, it defaults to: + check_warnings(("", Warning), quiet=True) + """ + quiet = kwargs.get('quiet') + if not filters: + filters = (("", Warning),) + # Preserve backward compatibility + if quiet is None: + quiet = True + return _filterwarnings(filters, quiet) + + +@contextlib.contextmanager +def check_no_warnings(testcase, message='', category=Warning, force_gc=False): + """Context manager to check that no warnings are emitted. + + This context manager enables a given warning within its scope + and checks that no warnings are emitted even with that warning + enabled. + + If force_gc is True, a garbage collection is attempted before checking + for warnings. This may help to catch warnings emitted when objects + are deleted, such as ResourceWarning. + + Other keyword arguments are passed to warnings.filterwarnings(). + """ + from test.support import gc_collect + with warnings.catch_warnings(record=True) as warns: + warnings.filterwarnings('always', + message=message, + category=category) + yield + if force_gc: + gc_collect() + testcase.assertEqual(warns, []) + + +@contextlib.contextmanager +def check_no_resource_warning(testcase): + """Context manager to check that no ResourceWarning is emitted. + + Usage: + + with check_no_resource_warning(self): + f = open(...) + ... + del f + + You must remove the object which may emit ResourceWarning before + the end of the context manager. + """ + with check_no_warnings(testcase, category=ResourceWarning, force_gc=True): + yield + + +def _filterwarnings(filters, quiet=False): + """Catch the warnings, then check if all the expected + warnings have been raised and re-raise unexpected warnings. + If 'quiet' is True, only re-raise the unexpected warnings. + """ + # Clear the warning registry of the calling module + # in order to re-raise the warnings. + frame = sys._getframe(2) + registry = frame.f_globals.get('__warningregistry__') + if registry: + registry.clear() + with warnings.catch_warnings(record=True) as w: + # Set filter "always" to record all warnings. Because + # test_warnings swap the module, we need to look up in + # the sys.modules dictionary. + sys.modules['warnings'].simplefilter("always") + yield WarningsRecorder(w) + # Filter the recorded warnings + reraise = list(w) + missing = [] + for msg, cat in filters: + seen = False + for w in reraise[:]: + warning = w.message + # Filter out the matching messages + if (re.match(msg, str(warning), re.I) and + issubclass(warning.__class__, cat)): + seen = True + reraise.remove(w) + if not seen and not quiet: + # This filter caught nothing + missing.append((msg, cat.__name__)) + if reraise: + raise AssertionError("unhandled warning %s" % reraise[0]) + if missing: + raise AssertionError("filter (%r, %s) did not catch any warning" % + missing[0]) + + +@contextlib.contextmanager +def save_restore_warnings_filters(): + old_filters = warnings.filters[:] + try: + yield + finally: + warnings.filters[:] = old_filters + + +def _warn_about_deprecation(): + warnings.warn( + "This is used in test_support test to ensure" + " support.ignore_deprecations_from() works as expected." + " You should not be seeing this.", + DeprecationWarning, + stacklevel=0, + ) |