master a111978: Count zero-length matches in `count-matches' correctly

[Lars Ingebrigtsen]

branch: master
commit a111978de8fa28256a208d823b68a37188dfa7f0
Author: Lars Ingebrigtsen <larsi@gnus.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Count zero-length matches in `count-matches' correctly
    
    * lisp/replace.el (how-many): Count zero-length matches correctly
    (bug#27359).
---
 lisp/replace.el            | 12 ++++++------
 test/lisp/replace-tests.el | 11 +++++++++++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/lisp/replace.el b/lisp/replace.el
index fe2cbc4..ed81097 100644
--- a/lisp/replace.el
+++ b/lisp/replace.el
@@ -1089,17 +1089,17 @@ a previously found match."
              rend (point-max)))
       (goto-char rstart))
     (let ((count 0)
-         opoint
          (case-fold-search
           (if (and case-fold-search search-upper-case)
               (isearch-no-upper-case-p regexp t)
             case-fold-search)))
       (while (and (< (point) rend)
-                 (progn (setq opoint (point))
-                        (re-search-forward regexp rend t)))
-       (if (= opoint (point))
-           (forward-char 1)
-         (setq count (1+ count))))
+                 (re-search-forward regexp rend t))
+        ;; Ensure forward progress on zero-length matches like "^$".
+        (when (and (= (match-beginning 0) (match-end 0))
+                   (not (eobp)))
+          (forward-char 1))
+       (setq count (1+ count)))
       (when interactive (message (ngettext "%d occurrence"
                                           "%d occurrences"
                                           count)
diff --git a/test/lisp/replace-tests.el b/test/lisp/replace-tests.el
index 2db570c..6d004e6 100644
--- a/test/lisp/replace-tests.el
+++ b/test/lisp/replace-tests.el
@@ -601,4 +601,15 @@ bound to HIGHLIGHT-LOCUS."
          (if (match-string 2) "R" "L")))
       (should (equal (buffer-string) after)))))
 
+(ert-deftest test-count-matches ()
+  (with-temp-buffer
+    (insert "oooooooooo")
+    (goto-char (point-min))
+    (should (= (count-matches "oo") 5))
+    (should (= (count-matches "o+") 1)))
+  (with-temp-buffer
+    (insert "o\n\n\n\no\n\n")
+    (goto-char (point-min))
+    (should (= (count-matches "^$") 4))))
+
 ;;; replace-tests.el ends here