Support for not following symlinks in pathlib.Path.is_dir()

[barneygale]

Feature or enhancement

Add a follow_symlinks argument to pathlib.Path.is_dir(), defaulting to True

Pitch

Pathlib's walk() and glob() implementations are built upon os.scandir(), which yields os.DirEntry objects. The interface for os.DirEntry is a rough subset of pathlib.Path, including the name attribute and is_dir() method.

Pathlib only ever calls os.scandir() via a private pathlib.Path._scandir() method, currently defined as follows:

    def _scandir(self):
        return os.scandir(self)

In future I'd like to add a pathlib.AbstractPath class with abstract stat(), iterdir() and open() methods.

The default implementation of AbstractPath._scandir() would use iterdir():

   def _scandir(self):
       return contextlib.nullcontext(list(self.iterdir()))

Note how it returns AbstractPath objects, and not DirEntry objects. This exploits the similarities of the Path and DirEntry APIs.

... but there's a problem!

The os.DirEntry.is_dir() method accepts a keyword-only follow_symlinks argument. Our globbing implementation requires us to set this argument. But the Path.is_dir() method does not accept this argument!

If we add a keyword-only follow_symlinks argument to Path.is_dir(), we make it compatible with os.DirEntry.is_dir(), which in turn allows us to build a glob() implementation upon user-defined stat() and iterdir() methods in a future AbstractPath class.

Previous discussion

General discussion of AbstractPath: https://discuss.python.org/t/make-pathlib-extensible/3428

We added a follow_symlinks argument to Path.exists() in #89769 / #29655.

Linked PRs

• GH-105793: Add follow_symlinks argument to pathlib.Path.is_dir() and is_file() #105794

[eryksun]

Path.is_file() may as well also support follow_symlinks, as is implemented for DirEntry.is_file().

[barneygale]

Implemented in:

• 3.13 / 219effa / GH-105793: Add follow_symlinks argument to pathlib.Path.is_dir() and is_file() #105794

Thank you Steve for the review and Eryk for the is_file() suggestion :-)