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import contextlib
import importlib
import sys
import warnings
@contextlib.contextmanager
def _ignore_deprecated_imports(ignore=True):
"""Context manager to suppress package and module deprecation
warnings when importing them.
If ignore is False, this context manager has no effect.
"""
if ignore:
with warnings.catch_warnings():
warnings.filterwarnings("ignore", ".+ (module|package)",
DeprecationWarning)
yield
else:
yield
def _save_and_remove_module(name, orig_modules):
"""Helper function to save and remove a module from sys.modules
Raise ImportError if the module can't be imported.
"""
# try to import the module and raise an error if it can't be imported
if name not in sys.modules:
__import__(name)
del sys.modules[name]
for modname in list(sys.modules):
if modname == name or modname.startswith(name + '.'):
orig_modules[modname] = sys.modules[modname]
del sys.modules[modname]
def _save_and_block_module(name, orig_modules):
"""Helper function to save and block a module in sys.modules
Return True if the module was in sys.modules, False otherwise.
"""
saved = True
try:
orig_modules[name] = sys.modules[name]
except KeyError:
saved = False
sys.modules[name] = None
return saved
def import_fresh_module(name, fresh=(), blocked=(), deprecated=False):
"""Import and return a module, deliberately bypassing sys.modules.
This function imports and returns a fresh copy of the named Python module
by removing the named module from sys.modules before doing the import.
Note that unlike reload, the original module is not affected by
this operation.
*fresh* is an iterable of additional module names that are also removed
from the sys.modules cache before doing the import.
*blocked* is an iterable of module names that are replaced with None
in the module cache during the import to ensure that attempts to import
them raise ImportError.
The named module and any modules named in the *fresh* and *blocked*
parameters are saved before starting the import and then reinserted into
sys.modules when the fresh import is complete.
Module and package deprecation messages are suppressed during this import
if *deprecated* is True.
This function will raise ImportError if the named module cannot be
imported.
"""
# NOTE: test_heapq, test_json and test_warnings include extra sanity checks
# to make sure that this utility function is working as expected
with _ignore_deprecated_imports(deprecated):
# Keep track of modules saved for later restoration as well
# as those which just need a blocking entry removed
orig_modules = {}
names_to_remove = []
_save_and_remove_module(name, orig_modules)
try:
for fresh_name in fresh:
_save_and_remove_module(fresh_name, orig_modules)
for blocked_name in blocked:
if not _save_and_block_module(blocked_name, orig_modules):
names_to_remove.append(blocked_name)
fresh_module = importlib.import_module(name)
except ImportError:
fresh_module = None
finally:
for orig_name, module in orig_modules.items():
sys.modules[orig_name] = module
for name_to_remove in names_to_remove:
del sys.modules[name_to_remove]
return fresh_module
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