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import importlib
from importlib import abc
from importlib import util
import unittest
from . import util as test_util
class CollectInit:
def __init__(self, *args, **kwargs):
self.args = args
self.kwargs = kwargs
def exec_module(self, module):
return self
class LazyLoaderFactoryTests(unittest.TestCase):
def test_init(self):
factory = util.LazyLoader.factory(CollectInit)
# E.g. what importlib.machinery.FileFinder instantiates loaders with
# plus keyword arguments.
lazy_loader = factory('module name', 'module path', kw='kw')
loader = lazy_loader.loader
self.assertEqual(('module name', 'module path'), loader.args)
self.assertEqual({'kw': 'kw'}, loader.kwargs)
def test_validation(self):
# No exec_module(), no lazy loading.
with self.assertRaises(TypeError):
util.LazyLoader.factory(object)
class TestingImporter(abc.MetaPathFinder, abc.Loader):
module_name = 'lazy_loader_test'
mutated_name = 'changed'
loaded = None
source_code = 'attr = 42; __name__ = {!r}'.format(mutated_name)
def find_spec(self, name, path, target=None):
if name != self.module_name:
return None
return util.spec_from_loader(name, util.LazyLoader(self))
def exec_module(self, module):
exec(self.source_code, module.__dict__)
self.loaded = module
class LazyLoaderTests(unittest.TestCase):
def test_init(self):
with self.assertRaises(TypeError):
util.LazyLoader(object)
def new_module(self, source_code=None):
loader = TestingImporter()
if source_code is not None:
loader.source_code = source_code
spec = util.spec_from_loader(TestingImporter.module_name,
util.LazyLoader(loader))
module = spec.loader.create_module(spec)
module.__spec__ = spec
module.__loader__ = spec.loader
spec.loader.exec_module(module)
# Module is now lazy.
self.assertIsNone(loader.loaded)
return module
def test_e2e(self):
# End-to-end test to verify the load is in fact lazy.
importer = TestingImporter()
assert importer.loaded is None
with test_util.uncache(importer.module_name):
with test_util.import_state(meta_path=[importer]):
module = importlib.import_module(importer.module_name)
self.assertIsNone(importer.loaded)
# Trigger load.
self.assertEqual(module.__loader__, importer)
self.assertIsNotNone(importer.loaded)
self.assertEqual(module, importer.loaded)
def test_attr_unchanged(self):
# An attribute only mutated as a side-effect of import should not be
# changed needlessly.
module = self.new_module()
self.assertEqual(TestingImporter.mutated_name, module.__name__)
def test_new_attr(self):
# A new attribute should persist.
module = self.new_module()
module.new_attr = 42
self.assertEqual(42, module.new_attr)
def test_mutated_preexisting_attr(self):
# Changing an attribute that already existed on the module --
# e.g. __name__ -- should persist.
module = self.new_module()
module.__name__ = 'bogus'
self.assertEqual('bogus', module.__name__)
def test_mutated_attr(self):
# Changing an attribute that comes into existence after an import
# should persist.
module = self.new_module()
module.attr = 6
self.assertEqual(6, module.attr)
def test_delete_eventual_attr(self):
# Deleting an attribute should stay deleted.
module = self.new_module()
del module.attr
self.assertFalse(hasattr(module, 'attr'))
def test_delete_preexisting_attr(self):
module = self.new_module()
del module.__name__
self.assertFalse(hasattr(module, '__name__'))
def test_module_substitution_error(self):
source_code = 'import sys; sys.modules[__name__] = 42'
module = self.new_module(source_code)
with test_util.uncache(TestingImporter.module_name):
with self.assertRaises(ValueError):
module.__name__
if __name__ == '__main__':
unittest.main()
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