Make a prefix go to the previous error

* lisp/textmodes/flyspell.el (flyspell-goto-next-error): Make a
prefix find the previous error (bug#50443).

1 files changed, 30 insertions, 21 deletions

diff --git a/lisp/textmodes/flyspell.el b/lisp/textmodes/flyspell.el
index 1094ef3e934..a893bc7b9ce 100644
--- a/lisp/textmodes/flyspell.el
+++ b/lisp/textmodes/flyspell.el
@@ -1714,25 +1714,32 @@ of a misspelled word removed when you've corrected it."
 ;;*---------------------------------------------------------------------*/
 ;;*    flyspell-goto-next-error ...                                     */
 ;;*---------------------------------------------------------------------*/
-(defun flyspell-goto-next-error ()
-  "Go to the next previously detected error.
+(defun flyspell-goto-next-error (&optional previous)
+  "Go to the next error.
+If PREVIOUS (interactively, the prefix), go to the previous error
+instead.
+
 In general FLYSPELL-GOTO-NEXT-ERROR must be used after
 FLYSPELL-BUFFER."
-  (interactive)
+  (interactive "P")
   (let ((pos (point))
-	(max (point-max)))
-    (if (and (eq (current-buffer) flyspell-old-buffer-error)
-	     (eq pos flyspell-old-pos-error))
-	(progn
-	  (if (= flyspell-old-pos-error max)
-	      ;; goto beginning of buffer
+	(max (if previous (point-min) (point-max))))
+    (when (and (eq (current-buffer) flyspell-old-buffer-error)
+	       (eq pos flyspell-old-pos-error))
+      (if previous
+          (if (= flyspell-old-pos-error max)
 	      (progn
-		(message "Restarting from beginning of buffer")
-		(goto-char (point-min)))
-	    (forward-word 1))
-	  (setq pos (point))))
-    ;; seek the next error
-    (while (and (< pos max)
+	        (message "Restarting from end of the buffer")
+	        (goto-char (point-max)))
+	    (forward-word -1))
+        (if (= flyspell-old-pos-error max)
+	    (progn
+	      (message "Restarting from beginning of buffer")
+	      (goto-char (point-min)))
+	  (forward-word 1)))
+      (setq pos (point)))
+    ;; Seek the next error.
+    (while (and (/= pos max)
 		(let ((ovs (overlays-at pos))
 		      (r '()))
 		  (while (and (not r) (consp ovs))
@@ -1740,13 +1747,15 @@ FLYSPELL-BUFFER."
 			(setq r t)
 		      (setq ovs (cdr ovs))))
 		  (not r)))
-      (setq pos (1+ pos)))
-    ;; save the current location for next invocation
-    (setq flyspell-old-pos-error pos)
-    (setq flyspell-old-buffer-error (current-buffer))
+      (setq pos (if previous (1- pos) (1+ pos))))
     (goto-char pos)
-    (if (= pos max)
-	(message "No more miss-spelled word!"))))
+    (when previous
+      (forward-word -1))
+    ;; Save the current location for next invocation.
+    (setq flyspell-old-pos-error (point))
+    (setq flyspell-old-buffer-error (current-buffer))
+    (when (= (point) max)
+      (message "No more miss-spelled words"))))
 
 ;;*---------------------------------------------------------------------*/
 ;;*    flyspell-overlay-p ...                                           */