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