From: Stephen Berman via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Gabriele Nicolardi <gabriele@medialab.sissa.it>,
71429@debbugs.gnu.org, Stefan Kangas <stefankangas@gmail.com>
Subject: bug#71429: Inconsistent y-or-n-p prompt behavior in Emacs Lisp
Date: Sat, 08 Jun 2024 15:59:11 +0200 [thread overview]
Message-ID: <87h6e3lemo.fsf@gmx.net> (raw)
In-Reply-To: <87cyoreqpd.fsf@gmx.net> (Stephen Berman's message of "Sat, 08 Jun 2024 11:20:14 +0200")
On Sat, 08 Jun 2024 11:20:14 +0200 Stephen Berman <stephen.berman@gmx.net> wrote:
> On Sat, 08 Jun 2024 11:24:50 +0300 Eli Zaretskii <eliz@gnu.org> wrote:
>
>>> Date: Sat, 8 Jun 2024 09:03:37 +0200
>>> From: Gabriele Nicolardi <gabriele@medialab.sissa.it>
>>>
>>> I have the following Emacs Lisp code:
>>>
>>> (progn
>>> (y-or-n-p "Test: ")
>>> (let ((search-spaces-regexp "\\(?:\\n?[\s\t]+\\|\n\\)?"))
>>> (y-or-n-p "Test: ")))
>>>
>>> The first prompt from the y-or-n-p function appears as expected:
>>>
>>> Test: (y or n)
>>>
>>> However, the second prompt appears differently:
>>>
>>> Test: (‘y’ or ‘n’)
>>>
>>> I’m trying to understand why the second prompt format changes. What causes this inconsistency in the
>>> y-or-n-p prompt?
>>>
>>> I suspect it might be related to the search-spaces-regexp variable or how Emacs handles interactive
>>> prompts, but I’m not sure. Any insights or explanations would be greatly appreciated!
>>
>> Stefan, can you please look into this? It sounds like some issue with
>> substitute-command-keys:
>>
>> (substitute-command-keys "(\\`y' or \\`n') ")
>> => #("(y or n) " 1 2 (font-lock-face help-key-binding face help-key-binding) 6 7 (font-lock-face help-key-binding face help-key-binding))
>>
>> But
>>
>> (let ((search-spaces-regexp "\\(?:\\n?[\s\t]+\\|\n\\)?"))
>> (substitute-command-keys "(\\`y' or \\`n') "))
>> => "(\\‘y’ or \\‘n’) "
>>
>> I actually don't understand why we use \\`y' and \\`n' in y-or-n-p.
>> Why those backslashes, and not just `y' and `n'? That's your change
>> in commit a36ecc408a. If I remove the backslashes, the results are
>> identical whether or not search-spaces-regexp is let-bound.
Without the backslashes the cond-clause in substitute-command-keys
handling sequences starting with "\" is skipped, so "y" and "n" do not
get the help-key-binding face property.
> Removing the final '?' in the regexp, i.e.
>
> (let ((search-spaces-regexp "\\(?:\\n?[\s\t]+\\|\n\\)"))
> (y-or-n-p "Test: "))
>
> results in the second prompt appearing like the first one. Likewise
> with '*', but not with '+':
>
> (let ((search-spaces-regexp " ?"))
> (y-or-n-p "Test: "))
> => Test: (\‘y’ or \‘n’)
>
> (let ((search-spaces-regexp " *"))
> (y-or-n-p "Test: "))
> => Test: (\‘y’ or \‘n’)
>
> (let ((search-spaces-regexp " +"))
> (y-or-n-p "Test: "))
> => Test: (y or n)
>
> (let ((search-spaces-regexp " "))
> (y-or-n-p "Test: "))
> => Test: (y or n)
Stepping through substitute-command-keys in Edebug, I see that when the
regexp ends in '?' or '*' the sexp (key-valid-p k) in
substitute-command-keys returns nil for k set to "y" and then to "n", so
these strings do not get the help-key-binding face property and "(\\`y'
or \\`n') " is returned to y-or-n-p unaltered. When the regexp does not
end in '?' or '*', (key-valid-p k) returns t for "y" and "n" and these
strings get propertized.
Stepping through key-valid-p, I see that when the regexp ends in '?' or
'*' the sexp (split-string keys " ") returns (#1="" "y" #1#) for keys
set to "y", and key-valid-p loops over this lists, and the first element
"" is an invalid key. When the regexp does not end in '?' or '*' the
split-string sexp in key-valid-p returns ("y"), and "y" is valid.
And stepping through split-string, I see that when the regexp ends in
'?' or '*', the invocation of string-match in the while-loop with args
REGEXP set to " ", STRING set to "y" and START set to 0 returns 0, which
results in "" being pushed onto the list both before and after "y",
hence returning (#1="" "y" #1#). When the regexp does not end in '?' or
'*', the string-match invocation returns nil and only "y" is pushed onto
the list.
Steve Berman
next prev parent reply other threads:[~2024-06-08 13:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-08 7:03 bug#71429: Inconsistent y-or-n-p prompt behavior in Emacs Lisp Gabriele Nicolardi
2024-06-08 8:24 ` Eli Zaretskii
2024-06-08 9:20 ` Stephen Berman via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-06-08 13:59 ` Stephen Berman via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2024-06-08 14:58 ` Eli Zaretskii
2024-06-08 15:30 ` Drew Adams via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-06-08 15:38 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-06-08 16:36 ` Eli Zaretskii
2024-06-08 17:41 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-06-08 18:08 ` Eli Zaretskii
2024-06-09 11:02 ` Stefan Kangas
2024-06-08 15:47 ` Stephen Berman via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-06-08 16:44 ` Eli Zaretskii
2024-06-09 11:01 ` Stefan Kangas
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