GNU bug report logs - #76528
30; Advising functions can cause docstring to be lost

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Message #8 received at 76528 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Jonas Bernoulli <jonas <at> bernoul.li>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 76528 <at> debbugs.gnu.org
Subject: Re: bug#76528: 30; Advising functions can cause docstring to be lost
Date: Mon, 24 Feb 2025 21:20:10 +0200

> Date: Mon, 24 Feb 2025 19:25:36 +0100
> From:  Jonas Bernoulli via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
> 
> Hello,
> 
> Depending on where the docstring is stored, advising a function can
> cause its original docstring to be lost.  This also affects 29.4 at
> least.
> 
> (defun embeded-docstr () "embeded docstr" nil)
> 
> (defun property-docstr () nil)
> (put 'property-docstr 'function-documentation "property docstr")
> 
> (defalias 'alias-docstr 'identity "alias docstr")
> 
> (defun maybe-loose-docstring (symbol)
>   (let ((a (documentation symbol))
>         (b nil)
>         (advice (lambda (fn &rest args) (apply fn args))))
>     (advice-add symbol :around advice)
>     (setq b (documentation symbol))
>     (advice-remove symbol advice)
>     `((,a) (,b) (,(documentation symbol)))))
> 
> (maybe-loose-docstring 'embeded-docstr)
> => (("embeded docstr\n\n(fn)")
>     ("embeded docstr\n\nThis function has :around advice: No documentation\n\n(fn)")
>     ("embeded docstr\n\n(fn)"))
> 
> (maybe-loose-docstring 'property-docstr)
> => (("property docstr")
>     ("\nThis function has :around advice: No documentation\n\n(fn)")
>     ("\n\n(fn)"))
> 
> (maybe-loose-docstring 'alias-docstr)
> => (("alias docstr")
>     ("Return the ARGUMENT unchanged.\n\nThis function has :around advice: No documentation\n\n(fn ARGUMENT)")
>     ("Return the ARGUMENT unchanged.\n\n(fn ARGUMENT)"))

Stefan, any comments?

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