87 lines
3.4 KiB
Python
87 lines
3.4 KiB
Python
"""Test that sys.modules is used properly by import."""
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from .. import util
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from . import util as import_util
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import sys
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from types import MethodType
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import unittest
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class UseCache(unittest.TestCase):
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"""When it comes to sys.modules, import prefers it over anything else.
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Once a name has been resolved, sys.modules is checked to see if it contains
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the module desired. If so, then it is returned [use cache]. If it is not
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found, then the proper steps are taken to perform the import, but
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sys.modules is still used to return the imported module (e.g., not what a
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loader returns) [from cache on return]. This also applies to imports of
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things contained within a package and thus get assigned as an attribute
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[from cache to attribute] or pulled in thanks to a fromlist import
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[from cache for fromlist]. But if sys.modules contains None then
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ImportError is raised [None in cache].
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"""
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def test_using_cache(self):
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# [use cache]
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module_to_use = "some module found!"
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with util.uncache(module_to_use):
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sys.modules['some_module'] = module_to_use
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module = import_util.import_('some_module')
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self.assertEqual(id(module_to_use), id(module))
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def test_None_in_cache(self):
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#[None in cache]
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name = 'using_None'
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with util.uncache(name):
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sys.modules[name] = None
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with self.assertRaises(ImportError):
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import_util.import_(name)
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def create_mock(self, *names, return_=None):
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mock = util.mock_modules(*names)
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original_load = mock.load_module
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def load_module(self, fullname):
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original_load(fullname)
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return return_
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mock.load_module = MethodType(load_module, mock)
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return mock
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# __import__ inconsistent between loaders and built-in import when it comes
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# to when to use the module in sys.modules and when not to.
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@import_util.importlib_only
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def test_using_cache_after_loader(self):
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# [from cache on return]
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with self.create_mock('module') as mock:
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with util.import_state(meta_path=[mock]):
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module = import_util.import_('module')
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self.assertEqual(id(module), id(sys.modules['module']))
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# See test_using_cache_after_loader() for reasoning.
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@import_util.importlib_only
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def test_using_cache_for_assigning_to_attribute(self):
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# [from cache to attribute]
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with self.create_mock('pkg.__init__', 'pkg.module') as importer:
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with util.import_state(meta_path=[importer]):
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module = import_util.import_('pkg.module')
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self.assertTrue(hasattr(module, 'module'))
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self.assertTrue(id(module.module), id(sys.modules['pkg.module']))
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# See test_using_cache_after_loader() for reasoning.
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@import_util.importlib_only
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def test_using_cache_for_fromlist(self):
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# [from cache for fromlist]
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with self.create_mock('pkg.__init__', 'pkg.module') as importer:
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with util.import_state(meta_path=[importer]):
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module = import_util.import_('pkg', fromlist=['module'])
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self.assertTrue(hasattr(module, 'module'))
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self.assertEqual(id(module.module),
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id(sys.modules['pkg.module']))
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def test_main():
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from test.support import run_unittest
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run_unittest(UseCache)
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if __name__ == '__main__':
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test_main()
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