Class CleanImport

Lib/test/support/import_helper.py:200–235

Context manager to force import to return a new module reference. This is useful for testing module-level behaviours, such as the emission of a DeprecationWarning on import. Use like this: with CleanImport("foo"): importlib.import_module("foo") # new reference

class CleanImport(object):
    """Context manager to force import to return a new module reference.

    This is useful for testing module-level behaviours, such as
    the emission of a DeprecationWarning on import.

    Use like this:

        with CleanImport("foo"):
            importlib.import_module("foo") # new reference

    If "usefrozen" is False (the default) then the frozen importer is
    disabled (except for essential modules like importlib._bootstrap).
    """

    def __init__(self, *module_names, usefrozen=False):
        self.original_modules = sys.modules.copy()
        for module_name in module_names:
            if module_name in sys.modules:
                module = sys.modules[module_name]
                # It is possible that module_name is just an alias for
                # another module (e.g. stub for modules renamed in 3.x).
                # In that case, we also need delete the real module to clear
                # the import cache.
                if module.__name__ != module_name:
                    del sys.modules[module.__name__]
                del sys.modules[module_name]
        self._frozen_modules = frozen_modules(usefrozen)

    def __enter__(self):
        self._frozen_modules.__enter__()
        return self

    def __exit__(self, *ignore_exc):
        sys.modules.update(self.original_modules)
        self._frozen_modules.__exit__(*ignore_exc)


class DirsOnSysPath(object):