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

[Augusto Stoffel <arstoffel@gmail.com>]

On Sun,  9 Jan 2022 at 11:10, Juri Linkov <juri@linkov.net> wrote:

> It seems the "Query replacing" prompt in perform-replace could just
> display the values of isearch-lazy-count-current and
> isearch-lazy-count-total.

Yes, I guess you are right.

> Or for asynchronous lazy-count a new hook needs to be run at the end
> of isearch-lazy-highlight-buffer-update in addition to the call of
> isearch-message.
>

That's what the patch does (but with a variable pointing to a function
instead of a hook, although this can be changed).  But note that it's
not enough to do something “in addition to the call of isearch-message”;
it's necessary to _suppress_ the call to isearch-message.

>>> But your patches are intended for a different feature - highlighting
>>> of matches in the buffer while entering an input string in the minibuffer.
>>>
>>> I wonder how many users need this feature, when it's easy to construct
>>> a query-replace string using highlighting/counting in isearch-mode,
>>> then type M-%
>>> (isearch-query-replace) that invokes query-replace with the
>>> query-replace string.
>>
>> Sure, this alternative method works.  But somehow it's not the way I
>> usually start a replace, and I think there's nothing wrong with that
>> preference :-)
>
> But this method is more limiting - no keys to pull text from the buffer
> like 'C-w' (isearch-yank-word-or-char) does in isearch-mode, no way
> to navigate to the first match like it's possible in isearch-mode, etc.
>

OTOH, you can't do a replace-in-region that way.

> Maybe then this feature could be added to read-regexp or even
> to read-from-minibuffer?  And activated by adding a setup function
> to minibuffer-setup-hook like other minibuffer's features do, such as
> icomplete-minibuffer-setup, minibuffer-depth-setup, rfn-eshadow-setup-minibuffer.
>
> Then maybe a new feature could be named e.g. "lazy-minibuffer"?

This is what the patch does, with code of this kind:

```
(let ((isearch-regexp t)
      ;; Whatever else isearch / lazy-highlight settings might be needed
      (isearch-lazy-count-display-function #'isearch-read-with-highlight-count))
  (minibuffer-with-setup-hook #'isearch-read-with-highlight-setup
    (read-from-minibuffer "Type a regexp with preview: ")))
```

There could be a convenience wrapper for this code, but I'm not sure
that makes much sense, because isearch and lazy-highlight have too many
parameters one might need to set so it's better to be explicit/flexible.