Yet another fix for copying properties by 'format'

* src/textprop.c (extend_property_ranges): Accept an additional
argument OLD_END, and only extend the end of a property range if
its original end is at OLD_END; all the other ranges are left
intact.  (Bug#23897)
* src/editfns.c (styled_format): Pass the original length of the
string to 'extend_property_ranges'.
* src/intervals.h (extend_property_ranges): Adjust prototype.

* test/src/editfns-tests.el (format-properties): Add tests for
bug#23897.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/textprop.c b/src/textprop.c
index aabd5671e76..7af8c698736 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -2043,18 +2043,19 @@ add_text_properties_from_list (Lisp_Object object, Lisp_Object list, Lisp_Object
    end-points to NEW_END.  */
 
 Lisp_Object
-extend_property_ranges (Lisp_Object list, Lisp_Object new_end)
+extend_property_ranges (Lisp_Object list, Lisp_Object old_end, Lisp_Object new_end)
 {
   Lisp_Object prev = Qnil, head = list;
   ptrdiff_t max = XINT (new_end);
 
   for (; CONSP (list); prev = list, list = XCDR (list))
     {
-      Lisp_Object item, beg, end;
+      Lisp_Object item, beg;
+      ptrdiff_t end;
 
       item = XCAR (list);
       beg = XCAR (item);
-      end = XCAR (XCDR (item));
+      end = XINT (XCAR (XCDR (item)));
 
       if (XINT (beg) >= max)
         {
@@ -2065,12 +2066,14 @@ extend_property_ranges (Lisp_Object list, Lisp_Object new_end)
           else
             XSETCDR (prev, XCDR (list));
         }
-      else if (XINT (end) != max)
+      else if ((end == XINT (old_end) && end != max)
+               || end > max)
         {
           /* Either the end-point is past the end of the new string,
              and we need to discard the properties past the new end,
              or the caller is extending the property range, and we
-             should update the end-point to reflect that.  */
+             should update all end-points that are on the old end of
+             the range to reflect that.  */
           XSETCAR (XCDR (item), new_end);
         }
     }