bug#6808: 24.0.50; Incomplete match highlighting with `query-replace-regexp'

["Johan Bockgård" <bojohan@gnu.org>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> The matches to be replaced by `query-replace-regexp' aren't highlighted
>> completely, although the replacement is correct.

[...]

> I'd guess that those incorrect matches are search with
> re-search-backward rather than re-search-forward.

Yes. replace-highlight does not update isearch-forward, so you get this
behavior if the previous isearch was a backward search (or in emacs -Q).

The following patch fixes this and two other problems:

* There is no lazy highlighting during replacement if the previous
  isearch set isearch-error (invalid regexp).

* A search that is started with C-s uses forward search for highlighting
  and one that is started with C-r uses backward search, but the
  highlighting is not updated if one switches direction in the middle
  (C-s followed by C-r or vice versa).



diff --git a/lisp/isearch.el b/lisp/isearch.el
index 89d50d6..1fe604d 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -2581,6 +2581,7 @@ since they have special meaning in a regexp."
 (defvar isearch-lazy-highlight-case-fold-search nil)
 (defvar isearch-lazy-highlight-regexp nil)
 (defvar isearch-lazy-highlight-space-regexp nil)
+(defvar isearch-lazy-highlight-forward nil)
 
 (defun lazy-highlight-cleanup (&optional force)
   "Stop lazy highlighting and remove extra highlighting from current buffer.
@@ -2620,7 +2621,9 @@ by other Emacs features."
                  (not (= (window-start)
                          isearch-lazy-highlight-window-start))
                  (not (= (window-end)   ; Window may have been split/joined.
-                         isearch-lazy-highlight-window-end))))
+                         isearch-lazy-highlight-window-end))
+		 (not (eq isearch-forward
+			  isearch-lazy-highlight-forward))))
     ;; something important did indeed change
     (lazy-highlight-cleanup t) ;kill old loop & remove overlays
     (when (not isearch-error)
@@ -2635,7 +2638,8 @@ by other Emacs features."
 	    isearch-lazy-highlight-case-fold-search isearch-case-fold-search
 	    isearch-lazy-highlight-regexp	isearch-regexp
             isearch-lazy-highlight-wrapped      nil
-	    isearch-lazy-highlight-space-regexp search-whitespace-regexp)
+	    isearch-lazy-highlight-space-regexp search-whitespace-regexp
+	    isearch-lazy-highlight-forward      isearch-forward)
       (unless (equal isearch-string "")
 	(setq isearch-lazy-highlight-timer
 	      (run-with-idle-timer lazy-highlight-initial-delay nil
@@ -2651,7 +2655,8 @@ Attempt to do the search exactly the way the pending Isearch would."
 	    (search-invisible nil)	; don't match invisible text
 	    (retry t)
 	    (success nil)
-	    (bound (if isearch-forward
+	    (isearch-forward isearch-lazy-highlight-forward)
+	    (bound (if isearch-lazy-highlight-forward
 		       (min (or isearch-lazy-highlight-end-limit (point-max))
 			    (if isearch-lazy-highlight-wrapped
 				isearch-lazy-highlight-start
@@ -2687,7 +2692,7 @@ Attempt to do the search exactly the way the pending Isearch would."
 	    (select-window isearch-lazy-highlight-window))
 	(save-excursion
 	  (save-match-data
-	    (goto-char (if isearch-forward
+	    (goto-char (if isearch-lazy-highlight-forward
 			   isearch-lazy-highlight-end
 			 isearch-lazy-highlight-start))
 	    (while looping
@@ -2700,7 +2705,7 @@ Attempt to do the search exactly the way the pending Isearch would."
 		    (let ((mb (match-beginning 0))
 			  (me (match-end 0)))
 		      (if (= mb me)	;zero-length match
-			  (if isearch-forward
+			  (if isearch-lazy-highlight-forward
 			      (if (= mb (if isearch-lazy-highlight-wrapped
 					    isearch-lazy-highlight-start
 					  (window-end)))
@@ -2720,7 +2725,7 @@ Attempt to do the search exactly the way the pending Isearch would."
 			  (overlay-put ov 'priority 1000)
 			  (overlay-put ov 'face lazy-highlight-face)
 			  (overlay-put ov 'window (selected-window))))
-		      (if isearch-forward
+		      (if isearch-lazy-highlight-forward
 			  (setq isearch-lazy-highlight-end (point))
 			(setq isearch-lazy-highlight-start (point)))))
 
@@ -2730,7 +2735,7 @@ Attempt to do the search exactly the way the pending Isearch would."
 			(setq looping nil
 			      nomore  t)
 		      (setq isearch-lazy-highlight-wrapped t)
-		      (if isearch-forward
+		      (if isearch-lazy-highlight-forward
 			  (progn
 			    (setq isearch-lazy-highlight-end (window-start))
 			    (goto-char (max (or isearch-lazy-highlight-start-limit (point-min))
diff --git a/lisp/replace.el b/lisp/replace.el
index d73692c..01d971f 100644
--- a/lisp/replace.el
+++ b/lisp/replace.el
@@ -1979,7 +1979,9 @@ make, or the user didn't cancel the call."
       (let ((isearch-string string)
 	    (isearch-regexp regexp)
 	    (search-whitespace-regexp nil)
-	    (isearch-case-fold-search case-fold))
+	    (isearch-case-fold-search case-fold)
+	    (isearch-forward t)
+	    (isearch-error nil))
 	;; Set isearch-word to nil because word-replace is regexp-based,
 	;; so `isearch-search-fun' should not use `word-search-forward'.
 	(if (and isearch-word isearch-regexp) (setq isearch-word nil))