writer.py 文件源码

def basedir(self):
        migrations_package_name, _ = MigrationLoader.migrations_module(self.migration.app_label)

        if migrations_package_name is None:
            raise ValueError(
                "Django can't create migrations for app '%s' because "
                "migrations have been disabled via the MIGRATION_MODULES "
                "setting." % self.migration.app_label
            )

        # See if we can import the migrations module directly
        try:
            migrations_module = import_module(migrations_package_name)
        except ImportError:
            pass
        else:
            try:
                return upath(module_dir(migrations_module))
            except ValueError:
                pass

        # Alright, see if it's a direct submodule of the app
        app_config = apps.get_app_config(self.migration.app_label)
        maybe_app_name, _, migrations_package_basename = migrations_package_name.rpartition(".")
        if app_config.name == maybe_app_name:
            return os.path.join(app_config.path, migrations_package_basename)

        # In case of using MIGRATION_MODULES setting and the custom package
        # doesn't exist, create one, starting from an existing package
        existing_dirs, missing_dirs = migrations_package_name.split("."), []
        while existing_dirs:
            missing_dirs.insert(0, existing_dirs.pop(-1))
            try:
                base_module = import_module(".".join(existing_dirs))
            except ImportError:
                continue
            else:
                try:
                    base_dir = upath(module_dir(base_module))
                except ValueError:
                    continue
                else:
                    break
        else:
            raise ValueError(
                "Could not locate an appropriate location to create "
                "migrations package %s. Make sure the toplevel "
                "package exists and can be imported." %
                migrations_package_name)

        final_dir = os.path.join(base_dir, *missing_dirs)
        if not os.path.isdir(final_dir):
            os.makedirs(final_dir)
        for missing_dir in missing_dirs:
            base_dir = os.path.join(base_dir, missing_dir)
            with open(os.path.join(base_dir, "__init__.py"), "w"):
                pass

        return final_dir