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import contextlib
import functools
import importlib
import re
import sys
import warnings
def import_deprecated(name):
"""Import *name* while suppressing DeprecationWarning."""
with warnings.catch_warnings():
warnings.simplefilter('ignore', category=DeprecationWarning)
return importlib.import_module(name)
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 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,
)
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