shutil: Inconsistent return types when using pathlib

Bug report

Bug description:

Using pathlib with shutil usually works, but there are some quirks when it comes to return types. As an example, see the copy function (but other functions are affected as well):

https://github.com/python/cpython/blob/67ded6a4faae29edff8e4f7886978e71ce116e33/Lib/shutil.py#L468-L484

In this case, if a Path object gets passed in as dst, it will be returned unchanged if it is not a directory, but a str will be returned if it is a directory. That's unexpected, the return type should be consistent, probably by always returning a str.

I assume that pathlib support is mostly incidental in shutil, considering that the latter predates the former. shutil should probably be reviewed for proper pathlib support at some point. (See also a few other pathlib/shutil related issues reported here.)

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-132820

Prüfe zuerst den verknüpften PR gh-132820 und untersuche dann Lib/shutil.py im Bereich von copy sowie die anderen im Bericht genannten pathlib-bezogenen Funktionen. Überprüfe die vorhandenen shutil-Tests und stelle sicher, dass die betroffenen Funktionen konsistente, dokumentierte Rückgabetypen haben, mit Tests, die Path-Ziele abdecken, die Verzeichnisse sind und die keine Verzeichnisse sind.