Re: `read-from-minibuffer' seems to always return a multibyte string, but why?

> From: Nickolai Dobrynin <[email protected]>
> Cc: [email protected]
> Date: Tue, 25 Aug 2026 16:11:45 +0200
> 
> Eli Zaretskii <[email protected]> writes:
> 
> >> From: Nickolai Dobrynin <[email protected]>
> >> Date: Tue, 25 Aug 2026 05:47:52 +0200
> >> 
> >> I ran M-x ielm, executed
> >> 
> >> (set-buffer-multibyte nil)
> >> (read-from-minibuffer "Input: ")
> >> 
> >> and got a multibyte string back.
> >
> > Please show exactly what you did.  If I do this:
> >
> >  emacs -Q
> >  M-: (set-buffer-multibyte nil) RET
> >  M-: (multibyte-string-p (read-from-minibuffer "? " nil nil nil nil nil t)) RET
> >
> > and type "foo RET" at the prompt, I get nil as the result, as
> > expected.
> 
> I evaluated the two forms above but did not use the -Q command line option.
> 
> I noticed that the final argument in your example is set to t. In my
> example, it defaulted to nil.
> 
> Your example does work as expected.

OK, so everything is fine, IMO, since the last argument should be
non-nil to force inheritance of multibyte-ness.

> >> By the way, a multibyte string was really what I wanted out of this. I
> >> just want to be sure that this behavior is not accidental.
> >
> > Why do you care, may I ask?
> 
> I've been looking at `gnus-search-make-spec' in gnus-search.el and
> asking myself what kind of string this function returns. The final
> argument in the call to `read-from-minibuffer' defaults to nil. I must
> have understood the meaning of that argument in reverse.

OK, but still: why did you care whether gnus-search-make-spec returns
a unibyte or a multibyte string?

You see, usually functions that return strings to the application
level (including UI) should always return multibyte strings when
non-ASCII characters are involved, and either multibyte or unibyte
strings when only ASCII characters are involved.  Anything else is
either a bug or a very special situation.

So you should always expect a multibyte string if there's non-ASCII
text, and complain if somehow that's not what you get.