Fix c-ts-common filling

* lisp/progmodes/c-ts-common.el:
(c-ts-common--fill-block-comment): Exclude the last line from filling if
it only has non-word characters like *=-.
* test/lisp/progmodes/c-ts-mode-resources/filling.erts: Fir the
multi-line test and add a single line test.

2 files changed, 18 insertions, 4 deletions

diff --git a/lisp/progmodes/c-ts-common.el b/lisp/progmodes/c-ts-common.el
index 022d21e11a1..674623a5e61 100644
--- a/lisp/progmodes/c-ts-common.el
+++ b/lisp/progmodes/c-ts-common.el
@@ -186,9 +186,9 @@ comment."
       ;; filling region.
       (when (not end-marker)
         (goto-char end)
-        (when (looking-back (rx "*/") 2)
-          (backward-char 2)
-          (skip-syntax-backward "-")
+        (forward-line 0)
+        (when (looking-at (rx (* (or (syntax whitespace) "*" "=" "-"))
+                              "*/" eol))
           (setq end (point))))
 
       ;; Let `fill-paragraph' do its thing.
diff --git a/test/lisp/progmodes/c-ts-mode-resources/filling.erts b/test/lisp/progmodes/c-ts-mode-resources/filling.erts
index e58b8e91c90..5425519b3d7 100644
--- a/test/lisp/progmodes/c-ts-mode-resources/filling.erts
+++ b/test/lisp/progmodes/c-ts-mode-resources/filling.erts
@@ -101,7 +101,7 @@ Name: Type 4
 =-=
 /*================================================================
  * woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy
- woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy
+ * woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy
  woooomy woooomy woooomy woooomy woooomy
  * ================================================================*/
 =-=
@@ -112,6 +112,20 @@ Name: Type 4
  * ================================================================*/
 =-=-=
 
+Name: Type 4 Single-line
+
+=-=
+/*================================================================
+ * woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy
+ * ================================================================*/
+=-=
+/*================================================================
+ * woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy
+ * woooomy woooomy
+ * ================================================================*/
+=-=-=
+
+
 Name: Type 5
 
 /* woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy woooomy