GNU bug report logs - #31150
Entries in load-path should not have trailing slashes

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Message #32 received at 31150 <at> debbugs.gnu.org (full text, mbox):

From: Arash Esbati <arash <at> gnu.org>
To: Radon Rosborough <radon.neon <at> gmail.com>, Radian LLC
 <contact+straight <at> radian.codes>
Cc: 31150 <at> debbugs.gnu.org
Subject: Re: bug#31150: Entries in load-path should not have trailing slashes
Date: Wed, 06 Mar 2024 10:15:46 +0100

Radon Rosborough <radon.neon <at> gmail.com> writes:

> When I perform a fresh build of AUCTeX from Git, I get the following
> code as part of tex-site.el:
>
>     (defvar TeX-lisp-directory
>       (expand-file-name "auctex" (file-name-directory load-file-name))
>       "The directory where most of the AUCTeX lisp files are located.
>     For the location of lisp files associated with
>     styles, see the variables TeX-style-* (hand-generated lisp) and
>     TeX-auto-* (automatically generated lisp).")
>
>     (add-to-list 'load-path TeX-lisp-directory)
>
> This is problematic. As the documentation for `load-path' states:
>
>     Use ‘directory-file-name’ when adding items to this path.
>
> But `TeX-lisp-directory' has a trailing slash. This seems like a bug
> to me. Can it be fixed?
>
> The reason this came up is that I maintain an Emacs package manager,
> straight.el. Once straight.el builds a package, it adds the directory
> to `load-path', using `directory-file-name' as specified by the
> documentation of `load-path'. But since AUCTeX insists on also adding
> its own entry to `load-path', and does so with a superfluous trailing
> slash, we end up with two duplicate entries. Under some
> configurations, this causes duplicate entries to appear when using M-x
> find-library.

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

Is this issue still present?  Looking at the docstring:

,----[ C-h v load-path RET ]
| load-path is a variable defined in ‘C source code’.
| 
| Its value is shown below.
| 
| List of directories to search for files to load.
| Each element is a string (directory file name) or nil (meaning
| ‘default-directory’).
| This list is consulted by the ‘require’ function.
| Initialized during startup as described in Info node ‘(elisp)Library Search’.
| Use ‘directory-file-name’ when adding items to this path.  However, Lisp
| programs that process this list should tolerate directories both with
| and without trailing slashes.
| 
|   This variable may be risky if used as a file-local variable.
|   Probably introduced at or before Emacs version 1.12.
| 
`----

You're correct about `directory-file-name', but the version with
trailing slash is also tolerated.  If `find-library' is confused by
"/foo/bar" and "/foo/bar/", isn't this more an Emacs issue?

Best, Arash

P.S. I also added another mail address of yours to this message.  Sorry
if you get this message twice.

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