bug#72176: 30.0.60; icomplete-vertical-mode failed to work with Error

[Dmitry Gutov]

Hi Eshel,

On 20/07/2024 19:48, Eshel Yaron wrote:
> Eli Zaretskii <eliz@gnu.org> writes:
>
> > > From: João Távora <joaotavora@gmail.com>
> > > Date: Sat, 20 Jul 2024 10:09:38 +0100
> > > Cc: Robert Pluim <rpluim@gmail.com>, 72176@debbugs.gnu.org, 
> > > aqua0210@foxmail.com,
> > >         visuweshm@gmail.com
> > >
> > > On Sat, Jul 20, 2024 at 7:05 AM Eli Zaretskii <eliz@gnu.org> wrote:
> > >
> > > > Adding João, who I think wrote this code.
> > >
> > > Don't understand root cause, but it's in the whereabouts of
> > > the current analysis, yes. I recall regexp is supposed to always
> > > match, because it has (presumably) been used for a previous
> > > filtering. This breakage would seem to be a consequence of
> > > 3b07d33059150 by Eshel Yaron which in turn seems to be fixing
> > > something stemming from some feature Dmitry added in
> > > 6b7ff60a5e71c in June. I went one commit before that one and
> > > the recipe didn't break.
> >
> > Thanks, I'm adding the guilty parties to this discussion.
>
> I'm afraid you missed your mark, because AFAICT it is Stefan Monnier
> that's behind the root cause of this issue, which goes back way before
> Dmitry's change or mine :)

Thanks for investigating! It might or might not be considered a bug (the 
behavior had been working out okay before our changes), but your 
proposal does make it more consistent, so I hope we can use it.

vc-annotate for lines in question points to commit 86957a0cd which 
references bug#11714. I _haven't_ been able to reproduce it with them 
commented out now - my guess it's because of the file-name-quote 
operation that had been added much later (the last comment in the bug 
mentions that functionality as a hypothetical).

So maybe they really are unnecessary now. Though the 
quoting-unquoting-requoting stuff is pretty gnarly, so it'd be great to 
get a go-ahead from Stefan as well.

> It is a bug in completion--sifn-requote, that leads to incorrect
> completion strings to be passed to completion-lazy-hilit.  It is not
> related to icomplete per se.  To see the issue, try the following:
>
> 1. emacs -Q
> 2. say C-x C-f, clear the minibuffer, and insert ~/.config/~/f
> 3. hit ? to pop the completions list
> 4. see something like:
>
> --8<---------------cut here---------------start------------->8---
> Click or type M-RET on a completion to select it.
> Type M-<down> or M-<up> to move point between completions.
>
> 6 possible completions:
> .config/~/foo.json      .config/~/foo.org       .config/~/foo.php
> .config/~/foo.py        .config/~/foo.py~       .config/~/foo.rs
> --8<---------------cut here---------------end--------------->8---
>
> Note the incorrect prefix ".config/~/", completions should appear as
> "foo.json", "foo.org", etc.
>
> The following diff fixes this for me (including the icomplete symptom),
> although I can't claim to fully understand completion--sifn-requote yet:
>
> diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
> index 31c365bf850..d0eb6b43c80 100644
> --- a/lisp/minibuffer.el
> +++ b/lisp/minibuffer.el
> @@ -3855,13 +3855,13 @@ completion--sifn-requote
>         ;; Second assumptions: If qpos is far from the end this can be a bit 
> slow,
>         ;; so we speed it up by doing a first loop that skips a word at a time.
>         ;; This word-sized loop is careful not to cut in the middle of env-vars.
> -      (while (let ((boundary (string-match "\\(\\$+{?\\)?\\w+\\W*\\'" qstr)))
> -               (and boundary
> -                    (progn
> -                      (setq qprefix (substring qstr 0 boundary))
> -                      (string-prefix-p uprefix
> -                                       (substitute-in-file-name qprefix)))))
> -        (setq qstr qprefix))
> +      ;; (while (let ((boundary (string-match "\\(\\$+{?\\)?\\w+\\W*\\'" 
> qstr)))
> +      ;;          (and boundary
> +      ;;               (progn
> +      ;;                 (setq qprefix (substring qstr 0 boundary))
> +      ;;                 (string-prefix-p uprefix
> +      ;;                                  (substitute-in-file-name qprefix)))))
> +      ;;   (setq qstr qprefix))
>         (let ((qpos (length qstr)))
>           (while (and (> qpos 0)
>                       (string-prefix-p uprefix