import contextlib
import imp
import importlib
import sys
import unittest
@contextlib.contextmanager
def uncache(*names):
"""Uncache a module from sys.modules.
A basic sanity check is performed to prevent uncaching modules that either
cannot/shouldn't be uncached.
"""
for name in names:
if name in ('sys', 'marshal', 'imp'):
raise ValueError(
"cannot uncache {0} as it will break _importlib".format(name))
try:
del sys.modules[name]
except KeyError:
pass
try:
yield
finally:
for name in names:
try:
del sys.modules[name]
except KeyError:
pass
@contextlib.contextmanager
def import_state(**kwargs):
"""Context manager to manage the various importers and stored state in the
sys module.
The 'modules' attribute is not supported as the interpreter state stores a
pointer to the dict that the interpreter uses internally;
reassigning to sys.modules does not have the desired effect.
"""
originals = {}
try:
for attr, default in (('meta_path', []), ('path', []),
('path_hooks', []),
('path_importer_cache', {})):
originals[attr] = getattr(sys, attr)
if attr in kwargs:
new_value = kwargs[attr]
del kwargs[attr]
else:
new_value = default
setattr(sys, attr, new_value)
if len(kwargs):
raise ValueError(
'unrecognized arguments: {0}'.format(kwargs.keys()))
yield
finally:
for attr, value in originals.items():
setattr(sys, attr, value)
class mock_modules(object):
"""A mock importer/loader."""
def __init__(self, *names):
self.modules = {}
for name in names:
if not name.endswith('.__init__'):
import_name = name
else:
import_name = name[:-len('.__init__')]
if '.' not in name:
package = None
elif import_name == name:
package = name.rsplit('.', 1)[0]
else:
package = import_name
module = imp.new_module(import_name)
module.__loader__ = self
module.__file__ = '<mock __file__>'
module.__package__ = package
module.attr = name
if import_name != name:
module.__path__ = ['<mock __path__>']
self.modules[import_name] = module
def __getitem__(self, name):
return self.modules[name]
def find_module(self, fullname, path=None):
if fullname not in self.modules:
return None
else:
return self
def load_module(self, fullname):
if fullname not in self.modules:
raise ImportError
else:
sys.modules[fullname] = self.modules[fullname]
return self.modules[fullname]
def __enter__(self):
self._uncache = uncache(*self.modules.keys())
self._uncache.__enter__()
return self
def __exit__(self, *exc_info):
self._uncache.__exit__(None, None, None)
class ImportModuleTests(unittest.TestCase):
"""Test importlib.import_module."""
def test_module_import(self):
# Test importing a top-level module.
with mock_modules('top_level') as mock:
with import_state(meta_path=[mock]):
module = importlib.import_module('top_level')
self.assertEqual(module.__name__, 'top_level')
def test_absolute_package_import(self):
# Test importing a module from a package with an absolute name.
pkg_name = 'pkg'
pkg_long_name = '{0}.__init__'.format(pkg_name)
name = '{0}.mod'.format(pkg_name)
with mock_modules(pkg_long_name, name) as mock:
with import_state(meta_path=[mock]):
module = importlib.import_module(name)
self.assertEqual(module.__name__, name)
def test_shallow_relative_package_import(self):
modules = ['a.__init__', 'a.b.__init__', 'a.b.c.__init__', 'a.b.c.d']
with mock_modules(*modules) as mock:
with import_state(meta_path=[mock]):
module = importlib.import_module('.d', 'a.b.c')
self.assertEqual(module.__name__, 'a.b.c.d')
def test_deep_relative_package_import(self):
# Test importing a module from a package through a relatve import.
modules = ['a.__init__', 'a.b.__init__', 'a.c']
with mock_modules(*modules) as mock:
with import_state(meta_path=[mock]):
module = importlib.import_module('..c', 'a.b')
self.assertEqual(module.__name__, 'a.c')
def test_absolute_import_with_package(self):
# Test importing a module from a package with an absolute name with
# the 'package' argument given.
pkg_name = 'pkg'
pkg_long_name = '{0}.__init__'.format(pkg_name)
name = '{0}.mod'.format(pkg_name)
with mock_modules(pkg_long_name, name) as mock:
with import_state(meta_path=[mock]):
module = importlib.import_module(name, pkg_name)
self.assertEqual(module.__name__, name)
def test_relative_import_wo_package(self):
# Relative imports cannot happen without the 'package' argument being
# set.
self.assertRaises(TypeError, importlib.import_module, '.support')
def test_main():
from test.test_support import run_unittest
run_unittest(ImportModuleTests)
if __name__ == '__main__':
test_main()