Re: Always-true predicate?

[chad <yandros@gmail.com>]

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On Fri, Feb 19, 2021 at 1:10 AM Eli Zaretskii <eliz@gnu.org> wrote:

> I must diverge somewhat here, and express my uneasiness, to say the
> least, with the recent-ish fashion of making too many user options
> have function values.  It makes "M-x set-variable" much less
> convenient than it should be, and it makes customizing such options
> harder for users who aren't proficient in Lisp.  We should limit such
> option values to the absolute minimum, IMO.  I'd very much prefer to
> have simple atomic values (symbols, numbers, or strings) that are then
> interpreted by the relevant commands to run the necessary code or call
> out to necessary subroutines to do the job.  I feel that some of us
> think that putting functions with the necessary code directly in the
> option's value is somehow "cleaner" or "more elegant".  I disagree.
>

I suspect that I ran into an instance of this recently, where the helpful
package (an extension that offers expanded help functions, basically) had
trouble in it's helpful-callable function with facemenu-face-menu. I
tracked the problem down to a bad interaction in helpful with this code in
facemenu.el:

(defvar facemenu-face-menu
>   [...])
> (defalias 'facemenu-face-menu facemenu-face-menu)


The problem that I get is:

Debugger entered--Lisp error: (wrong-type-argument sequencep t)
>   mapconcat(identity (t) " ")
>   s-join(" " (t))
>   helpful--signature(facemenu-face-menu)
>   helpful-update()
>   helpful-callable(facemenu-face-menu)
>   funcall-interactively(helpful-callable facemenu-face-menu)
>   call-interactively(helpful-callable nil nil)
>   command-execute(helpful-callable)


I'm not familiar with the (defalias 'foo foo) idiom, so maybe it should be
expected to work, and it's just a bug in helpful. (I reported it to the
package maintainers already, with a note that I'd mention it here.) There
are a few other instances of in emacs that I found with a quick search, and
they also cause similar trouble for helpful.

Is this an example of an accidental functional value, as I originally
expected, or am I barking up the wrong tree and instead just looking at a
parsing bug? (My lisp is largely self taught and started with Scheme, so
these parts of elisp are murky to me.)

Thanks,
~Chad

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