Promote _delete member of TemporaryDirectory to delete

Feature or enhancement

Proposal:

TemporaryDirectory.__delete__ gained a delete parameter to support retaining temporary files for diagnostic purposes.

In a running system, you may wish gather diagnostic files on failure, or when a specific signal is received. Supporting this fully requires allowing the decision of whether to delete files to be made after the TemporaryDirectory has been __enter__ed.

Assigning to _delete can achieve this effect, but _delete is not part of the public interface.

Therefore, I propose changing TemporaryDirectory._delete to TemporaryDirectory.delete.

Example use to retain temporary files on error:

with TemporaryDirectory() as temp_dir:
    try:
        thing_that_may_raise()
    except Exception:
        temp_dir.delete = False
        raise

Alternatives considered:

• Provide a function to control this behaviour
  • We can always turn delete into a property if necessary
• Users can provide subclasses of TemporaryDirectory to achieve this
  • Temporary Directory doesn't have enough of a public API for this to be viable. Using the private API would be morally equivalent to modifying _delete, and modifying _delete would be easier.
• Users can provide a wrapper to prevent __exit__ from being called
  • __del__ might be implemented in the future, as it is for TemporaryFile.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-128643

Start with TemporaryDirectory and its enter/exit lifecycle, focusing on how the deletion decision is stored and used after entering the context. Review the linked PR gh-128643 for the work already underway; done means the public delete attribute supports changing cleanup behavior after enter.