[Python-Dev] pathlib handling of trailing slash (Issue #21039)

[Isaac Schwabacher]

pathlib.Path currently strips trailing slashes from pathnames, but this behavior contradicts POSIX (http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_12), which specifies that the resolution of the pathname of a symbolic link to a directory in the context of a function that operates on symbolic links shall depend on whether the pathname has a trailing slash:

> 4.12 Pathname Resolution
> ========================
>
> [...]
>
> A pathname that contains at least one non- <slash> character and that ends with one or more trailing <slash> characters shall not be resolved successfully unless the last pathname component before the trailing <slash> characters names an existing directory or a directory entry that is to be created for a directory immediately after the pathname is resolved. Interfaces using pathname resolution may specify additional constraints[1] when a pathname that does not name an existing directory contains at least one non- <slash> character and contains one or more trailing <slash> characters.
>
> If a symbolic link is encountered during pathname resolution, the behavior shall depend on whether the pathname component is at the end of the pathname and on the function being performed. If all of the following are true, then pathname resolution is complete:
>
> 1. This is the last pathname component of the pathname.
> 2. The pathname has no trailing <slash>.
> 3. The function is required to act on the symbolic link itself, or certain arguments direct that the function act on the symbolic link itself.
>
> In all other cases, the system shall prefix the remaining pathname, if any, with the contents of the symbolic link. [...]

The following sentence appeared in an earlier version of POSIX (http://pubs.opengroup.org/onlinepubs/009604499/basedefs/xbd_chap04.html#tag_04_11) but has since been removed:

> A pathname that contains at least one non-slash character and that ends with one or more trailing slashes shall be resolved as if a single dot character ( '.' ) were appended to the pathname.

Is this important enough to preserve trailing slashes?

- Isaac Schwabacher