Subject: Re: bug#53126: 29.0.50; [PATCH] Lazy highlight/count when reading query-replace string, etc.

From: Augusto Stoffel <[email-masked]>
Date: Fri, 01 Apr 2022 11:06:46 +0200

On Sun, 27 Mar 2022 at 10:46, Juri Linkov <[email-masked]> wrote:

>> Lazy highlight is controlled by lots of variables.  These variables need
>> to be set for the duration of the minibuffer session that reads the
>> replacement strings.  If we move this to a separate function, we can't
>> use 'let' anymore, so we basically need to reinvent the dynamic scoping
>> feature of Elisp (i.e., save the current values, set the variables to
>> new values, then restore the old values in some hook).  And an even ugly
>> workaround would be needed to replace the necessary condition-case.  Or
>> do I misunderstand you altogether?
>
> Do you think a macro could help to make this function short again?

That could be done, of course, but I'm pretty sure that this macro would
be used exactly once.  I don't think we should have a general-purpose
macro to set up the lazy highlighting for arbitrary minibuffer commands,
because complex cases like query-replace will be rare, and in any case
we can't anticipate all special requirements.

Anyway, should I refactor my patch to use a macro?

Something else that could make 'query-replace-read-args' slightly
shorter is to define

    (defun replace-regexp-function (delimited-flag)
      (or replace-regexp-function
          delimited-flag
          (and replace-char-fold
               (not regexp-flag)
               #'char-fold-to-regexp)))

This function could be used in 3 different places in replace.el.

> Then when you would want to add highlighting to the minibuffer
> reading the TO part of replacement too or to other minibuffers,
> it would be easy to just add a single line with that macro.

Right, a preview of the replacement text will also need some extra work.
This will probably involve some extension to
'isearch-lazy-highlight-update', making it even more complicated...