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

まずリンクされた PR gh-132820 を確認し、次に Lib/shutil.py の copy 周辺と、レポートで言及されているその他の pathlib 関連関数を調査してください。既存の shutil テストを確認し、影響を受ける関数の戻り値の型が一貫してドキュメント化されていることを、ディレクトリである Path 宛先とディレクトリではない Path 宛先を対象とするテストで確認してください。