Repository: pypa/pip
File: src/pip/_internal/operations/build/build_tracker.py (Python)

Code before:
                target[name] = original_value


@contextlib.contextmanager
def get_build_tracker() -> Generator["BuildTracker", None, None]:
    root = os.environ.get("PIP_BUILD_TRACKER")
    with contextlib.ExitStack() as ctx:
        if root is None:
            root = ctx.enter_context(TempDirectory(kind="build-tracker")).path
            ctx.enter_context(update_env_context_manager(PIP_BUILD_TRACKER=root))
            logger.debug("Initialized build tracking at %s", root)

        with BuildTracker(root) as tracker:
            yield tracker


class TrackerId(str):
    """Uniquely identifying string provided to the build tracker."""


class BuildTracker:
    """Ensure that an sdist cannot request itself as a setup requirement.

    When an sdist is prepared, it identifies its setup requirements in the
    context of ``BuildTracker#track()``. If a requirement shows up recursively, this
    raises an exception. This stops fork bombs embedded in malicious packages."""

    def __init__(self, root: str) -> None:
        self._root = root
        self._entries: Dict[TrackerId, InstallRequirement] = {}
        logger.debug("Created build tracker: %s", self._root)

    def __enter__(self) -> "BuildTracker":
        logger.debug("Entered build tracker: %s", self._root)
        return self

    def __exit__(
        self,
        exc_type: Optional[Type[BaseException]],
        exc_val: Optional[BaseException],
        exc_tb: Optional[TracebackType],
    ) -> None:
        self.cleanup()

    def _entry_path(self, key: TrackerId) -> str:
        hashed = hashlib.sha224(key.encode()).hexdigest()
        return os.path.join(self._root, hashed)

    def add(self, req: InstallRequirement, key: TrackerId) -> None:
        """Add an InstallRequirement to build tracking."""


Review comment (suggestion):
```suggestion
    raises an exception.

    This stops fork bombs embedded in malicious packages."""
```

This makes the point that this is about fork bomb protection more obvious. I don't know about others, but for me, the long and complex discussions about exposure to, and prevention of, fork bombs resulting from PEP 518 support still brings back memories. So making it as clear as possible that "hey, don't mess with this unless you know what you're doing" is worthwhile.

Code after:
                target[name] = original_value


@contextlib.contextmanager
def get_build_tracker() -> Generator["BuildTracker", None, None]:
    root = os.environ.get("PIP_BUILD_TRACKER")
    with contextlib.ExitStack() as ctx:
        if root is None:
            root = ctx.enter_context(TempDirectory(kind="build-tracker")).path
            ctx.enter_context(update_env_context_manager(PIP_BUILD_TRACKER=root))
            logger.debug("Initialized build tracking at %s", root)

        with BuildTracker(root) as tracker:
            yield tracker


class TrackerId(str):
    """Uniquely identifying string provided to the build tracker."""


class BuildTracker:
    """Ensure that an sdist cannot request itself as a setup requirement.

    When an sdist is prepared, it identifies its setup requirements in the
    context of ``BuildTracker.track()``. If a requirement shows up recursively, this
    raises an exception.

    This stops fork bombs embedded in malicious packages."""

    def __init__(self, root: str) -> None:
        self._root = root
        self._entries: Dict[TrackerId, InstallRequirement] = {}
        logger.debug("Created build tracker: %s", self._root)

    def __enter__(self) -> "BuildTracker":
        logger.debug("Entered build tracker: %s", self._root)
        return self

    def __exit__(
        self,
        exc_type: Optional[Type[BaseException]],
        exc_val: Optional[BaseException],
        exc_tb: Optional[TracebackType],
    ) -> None:
        self.cleanup()

    def _entry_path(self, key: TrackerId) -> str:
        hashed = hashlib.sha224(key.encode()).hexdigest()
        return os.path.join(self._root, hashed)

    def add(self, req: InstallRequirement, key: TrackerId) -> None: