bug#46469: 27.1; `isearch-del-char' should move point further back

[Juri Linkov <juri@linkov.net>]

>> But this change will cause a problem to me.  Usually, I type 'C-s'
>> several times with a non-empty search string to arrive to Nth occurrence.
>> Then to be able to continue the search with a shorter string, I remove
>> some characters from the search string with 'C-M-d' (isearch-del-char).
>> Then continue searching with 'C-s' from the same place.  But with the patch,
>> 'C-M-d' unexpectedly jumps to a previous match, and every next 'C-M-d'
>> jumps back it its previous match that makes no sense.
>
> I can verify this.  But I think you just found a related but independent
> issue.  Consider this example:
>
> (progn
>   (save-excursion (insert "a1 b2 a3"))
>   (isearch-mode t t)
>   (isearch-printing-char ?a)
>   (isearch-repeat-forward)
>   (isearch-printing-char ?\\)
>   (isearch-printing-char ?|)
>   (isearch-printing-char ?b))
>
> When "\\|b" is added to search string, the point is at "3".  So it
> shouldn't move, right?  But instead it goes back to "2".
>
> Do you get the same behavior?

I tested it in non-regexp mode, and the aforementioned use case is also
for non-regexp mode.

But in the regexp mode, maybe what you found is a bug.