The docs for the venv module, EnvBuilder class, ensure_directories method, describe behavior that doesn't match what its actual behavior is, (and what the code is).  I propose to update the documentation of the API to match the actual behavior.

https://docs.python.org/3.9/library/venv.html#venv.EnvBuilder.ensure_directories

The last sentence for ensure_directories(env_dir) reads:
The directories are allowed to exist already, as long as either clear or upgrade were specified to allow operating on an existing environment directory.

After testing and looking at the code (including past commits back over 6 years), this is not true.  ensure_directories completely disregards the `upgrade` attribute.  Also it allows directories to exist already unconditionally (always operating without error), whether the `clear` attribute is set or not.  In addition, if `clear` is not set, it doesn't make any changes to the directories, but helpfully still returns the context of venv paths.

Ref: https://github.com/python/cpython/blob/3ce35bfbbe29664942f9a8c50c177a4575a31934/Lib/venv/__init__.py#L95

To clarify my intent: I'd really love a way to get the paths info from context from an existing native venv without affecting the directories of the venv.  It seems like this is what ensure_directories *actually* does if clear==False.  I'm hoping that this is also something that could be pledged in the API and noted in the documentation so this behavior can be relied on.

New changeset 4bcef2bb48b3fd82011a89c1c716421b789f1442 by Matthew Clapp in branch 'main':
bpo-44388: Update venv EnvBuilder.ensure_directories() docs. (GH-26663)
https://github.com/python/cpython/commit/4bcef2bb48b3fd82011a89c1c716421b789f1442