Repository: pypa/pip
File: src/pip/_internal/req/req_uninstall.py (Python)

Code before:
                    os.unlink(new_path)
                elif os.path.isdir(new_path):
                    rmtree(new_path)
                renames(path, new_path)
            except OSError as ex:
                logger.error("Failed to restore %s", new_path)
                logger.debug("Exception: %s", ex)

        self.commit()

    @property
    def can_rollback(self) -> bool:
        return bool(self._moves)


class UninstallPathSet:
    """A set of file paths to be removed in the uninstallation of a
    requirement."""

    def __init__(self, dist: BaseDistribution) -> None:
        self._paths: Set[str] = set()
        self._refuse: Set[str] = set()
        self._pth: Dict[str, UninstallPthEntries] = {}
        self._dist = dist
        self._moved_paths = StashedUninstallPathSet()
        normalize_path_cached.cache_clear()

    def _permitted(self, path: str) -> bool:
        """
        Return True if the given path is one we are permitted to
        remove/modify, False otherwise.

        """
        return is_local(path)

    def add(self, path: str) -> None:
        head, tail = os.path.split(path)

        # we normalize the head to resolve parent directory symlinks, but not
        # the tail, since we only want to uninstall symlinks, not their targets
        path = os.path.join(normalize_path_cached(head), os.path.normcase(tail))

        if not os.path.exists(path):
            return
        if self._permitted(path):
            self._paths.add(path)
        else:
            self._refuse.add(path)

        # __pycache__ files can show up after 'installed-files.txt' is created,
        # due to imports

Review comment (performance):
It seems very weird to me instantiating a new object of this class has a global side effect. The cache should probably live on this object instead of a global function?

Code after:
                if os.path.isfile(new_path) or os.path.islink(new_path):
                    os.unlink(new_path)
                elif os.path.isdir(new_path):
                    rmtree(new_path)
                renames(path, new_path)
            except OSError as ex:
                logger.error("Failed to restore %s", new_path)
                logger.debug("Exception: %s", ex)

        self.commit()

    @property
    def can_rollback(self) -> bool:
        return bool(self._moves)


class UninstallPathSet:
    """A set of file paths to be removed in the uninstallation of a
    requirement."""

    def __init__(self, dist: BaseDistribution) -> None:
        self._paths: Set[str] = set()
        self._refuse: Set[str] = set()
        self._pth: Dict[str, UninstallPthEntries] = {}
        self._dist = dist
        self._moved_paths = StashedUninstallPathSet()
        # Create local cache of normalize_path results. Creating an UninstallPathSet
        # can result in hundreds/thousands of redundant calls to normalize_path with
        # the same args, which hurts performance.
        self._normalize_path_cached = functools.lru_cache()(normalize_path)

    def _permitted(self, path: str) -> bool:
        """
        Return True if the given path is one we are permitted to
        remove/modify, False otherwise.

        """
        # aka is_local, but caching normalized sys.prefix
        if not running_under_virtualenv():
            return True
        return path.startswith(self._normalize_path_cached(sys.prefix))

    def add(self, path: str) -> None:
        head, tail = os.path.split(path)

        # we normalize the head to resolve parent directory symlinks, but not
        # the tail, since we only want to uninstall symlinks, not their targets
        path = os.path.join(self._normalize_path_cached(head), os.path.normcase(tail))

        if not os.path.exists(path):
            return