GNU bug report logs - #79282
30.1; scheme-mode docstrings not highlighting with font-lock-doc-face

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Joe <jjbigorra <at> gmail.com>, Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 79282 <at> debbugs.gnu.org
Subject: bug#79282: 30.1; scheme-mode docstrings not highlighting with font-lock-doc-face
Date: Thu, 21 Aug 2025 09:39:29 +0300

> From: Joe <jjbigorra <at> gmail.com>
> Date: Wed, 20 Aug 2025 23:54:37 +0200
> 
> Dear Emacs Maintainers,
> 
> I am writing to report an issue I've observed in scheme-mode,
> specifically concerning the highlighting of docstrings. In scheme-mode
> (which inherits from lisp-mode), docstrings are currently being
> displayed as regular strings, using `font-lock-string-face', instead
> of being highlighted with `font-lock-doc-face'.
> 
> I expected docstrings in Scheme code, similar to those in Elisp or
> Common Lisp modes, should be highlighted distinctly using
> `font-lock-doc-face' for better readability and semantic distinction.
> I noticed in Elisp and Common Lisp this works perfectly, for all forms
> and variants (variables, defmethods, defun, etc.)
> 
> The problem is, when defining functions or macros in scheme-mode with
> a docstring, the docstring string literal is treated identically to
> any other string literal in terms of font locking.
> 
> I am a bit of a newbie when it comes to the lower levels of Emacs, and
> its modes, but I have looked into the source code of scheme-mode and
> it appears to contain the necessary functionality to correctly
> identify and highlight docstrings. For instance, I found lines such as
> :
> 
> (put 'define* 'scheme-doc-string-elt 2)
> 
> which seems to properly register docstring elements for font locking.
> This suggests that the mechanism for identifying docstrings is in
> place, but perhaps the application of font-lock-doc-face isn't
> occurring as intended, or there's an interaction issue with
> lisp-mode's inheritance.
> 
> Example (for illustration and clarity purposes):
> 
> (define (my-function arg)
>   "This is a docstring for my-function."
>   (+ arg 1))
> 
> In the example above, the string "This is a docstring for
> my-function." now appears with the font-lock-string-face , when it
> should instead be using font-lock-doc-face.
> 
> I run Emacs on Guix btw.
> 
> I would appreciate it if you could investigate this issue. Thank you
> for your time and dedication to maintaining the allmighty Emacs.

Stefan, any suggestions?

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