bug#40808: 27.0.91; inaccuracy in isearch-lazy-count

[Juri Linkov <juri@linkov.net>]

> When using isearch with isearch-lazy-count in org mode with heading
> collapsed isearch gives wrong number of matches (both total & current).
>
> Reproducing it is simple just enable isearch-lazy-count and perform
> isearch in org buffer with collapsed heading.

Thanks for bringing up this question, it will help to fix this feature
for the upcoming release.  I tend to agree that isearch-lazy-count
should show the number of *all* matches in the buffer, even the matches that
are invisible, and that can be opened when visited by isearch navigation.

Eli, do you agree with this patch for emacs-27.  It counts all matches, even
invisible.  And also it fixes an old bug existed in previous Emacs versions
where lazy-highlight didn't update lazy-highlighting when a hidden outline
was automatically opened at the end of the file (I noticed this bug only now).

So the condition ‘(eq search-invisible 'open)’ fixes an old bug, and
the condition ‘isearch-lazy-count’ fixes the new feature added in emacs-27:

diff --git a/lisp/isearch.el b/lisp/isearch.el
index e13a4dda83..ed1097c5ea 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -319,7 +319,7 @@ isearch-lazy-count
   "Show match numbers in the search prompt.
 When both this option and `isearch-lazy-highlight' are non-nil,
 show the current match number and the total number of matches
-in the buffer (or its restriction)."
+in the buffer (or its restriction), including all hidden matches."
   :type 'boolean
   :group 'lazy-count
   :group 'isearch
@@ -3869,7 +3871,8 @@ isearch-lazy-highlight-search
 	    (isearch-regexp-lax-whitespace
 	     isearch-lazy-highlight-regexp-lax-whitespace)
 	    (isearch-forward isearch-lazy-highlight-forward)
-	    (search-invisible nil)	; don't match invisible text
+            ;; don't match invisible text unless it can open or counting matches
+            (search-invisible (or (eq search-invisible 'open) isearch-lazy-count))
 	    (retry t)
 	    (success nil))
 	;; Use a loop like in `isearch-search'.