GNU bug report logs - #63345
28.2; provided-mode-derived-p doesn't work when passed an alias in MODES

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#63345: closed (28.2; provided-mode-derived-p doesn't work
 when passed an alias in MODES)
Date: Mon, 08 May 2023 11:31:02 +0000

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Your message dated Mon, 08 May 2023 14:31:43 +0300
with message-id <83o7mvcb4w.fsf <at> gnu.org>
and subject line Re: bug#63345: 28.2; provided-mode-derived-p doesn't work when passed an alias in MODES
has caused the debbugs.gnu.org bug report #63345,
regarding 28.2; provided-mode-derived-p doesn't work when passed an alias in MODES
to be marked as done.

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63345: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=63345
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From: Damien Cassou <damien <at> cassou.me>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.2; provided-mode-derived-p doesn't work when passed an alias in
 MODES
Date: Sun, 07 May 2023 11:49:37 +0200

Hi,

The function `provided-mode-derived-p` (used by `derived-mode-p`) has
the code below. The first 3 lines of the function takes care of
converting the first argument MODE if it is an alias (as
`javascript-mode` is an alias for `js-mode`). This works great when
calling the function this way:

  (provided-mode-derived-p 'javascript-mode 'prog-mode)
    ⇒ prog-mode

But if the second argument MODES contains an alias, the code has no
conversion mechanism and the line below returns nil even though I
expect it to return non-nil:

  (provided-mode-derived-p 'javacript-mode 'javascript-mode)
    ⇒ nil

Is that a bug?

(defun provided-mode-derived-p (mode &rest modes)
  "Non-nil if MODE is derived from one of MODES.
Uses the `derived-mode-parent' property of the symbol to trace backwards.
If you just want to check `major-mode', use `derived-mode-p'."
  ;; If MODE is an alias, then look up the real mode function first.
  (when-let ((alias (symbol-function mode)))
    (when (symbolp alias)
      (setq mode alias)))
  (while
      (and
       (not (memq mode modes))
       (let* ((parent (get mode 'derived-mode-parent))
              (parentfn (symbol-function parent)))
         (setq mode (if (and parentfn (symbolp parentfn)) parentfn parent)))))
  mode)

-- 
Damien Cassou

"Success is the ability to go from one failure to another without
losing enthusiasm." --Winston Churchill

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Damien Cassou <damien <at> cassou.me>
Cc: monnier <at> iro.umontreal.ca, 63345-done <at> debbugs.gnu.org
Subject: Re: bug#63345: 28.2; provided-mode-derived-p doesn't work when
 passed an alias in MODES
Date: Mon, 08 May 2023 14:31:43 +0300

> From: Damien Cassou <damien <at> cassou.me>
> Cc: 63345 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
> Date: Mon, 08 May 2023 06:56:05 +0200
> 
> Stefan Monnier <monnier <at> iro.umontreal.ca> writes:
> > `js-mode` is the right value to use there, indeed.
> 
> Very good, thank you. In this case I would close the issue.

Thanks, done.

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