Intentional reuse of deleted root dir in RequirementTracker

[gar1t]

The constructor uses an environment variable to cache the temp dir it creates:

https://github.com/pypa/pip/blob/18.0/src/pip/_internal/req/req_tracker.py#L17-L25

But RequirementTracker objects are context managers that delete the root dir:

https://github.com/pypa/pip/blob/18.0/src/pip/_internal/req/req_tracker.py#L31-L32
https://github.com/pypa/pip/blob/18.0/src/pip/_internal/req/req_tracker.py#L65-L67

It's not obvious to me looking at the code or associated commit messages what the goal of the root dir reuse is.

[benoit-pierre]

See #5336.

[gar1t]

I see there's a test that removes any PIP_REQ_TRACKER env, but I don't see where anyone sets that. Is the intention that a user will interface with pip via the environment?

I'm happy to put a PR together but I don't understand the intended behavior.

[benoit-pierre]

No! You should not use that, it's for PIP internal use.

[gar1t]

Nonetheless, I hope the maintainers can see the bug here, regardless of the intent.

Feel free to ignore and close!

[benoit-pierre]

I still don't understand what is the bug.

[benoit-pierre]

The initial pip process (e.g. the one spawned by the user pip install ...) will create a temporary directory, and share it with sub-processes for tracking requirements during the prepare phase.

[gar1t]

The class uses the environment to remember the first temporary dir it creates, effectively using the process environment as global state. It never un-remembers this. So that root is stuck forever once it's defined in os.environ.

If a tracker object is used as a context manager, when the context exits, __exit__ is called and the temp directory is deleted. It's never re-created and there's no way to un-remember it.

Code that writes to that directory, assuming it already exists, fails.

[benoit-pierre]

Again, what's the problem? Unless you're using multiple call to pip's main from python, something that is specifically not supported!

[gar1t]

I can see why it's not supported!

I'll go ahead and close this since you don't consider the behavior to be a bug.

[benoit-pierre]

See my comment for your use case.

[gar1t]

Terrific - thank you!

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.