correctly mark changed regions for set_text

src/nvim/api/buffer.c

@@ -722,7 +722,8 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer,
                  kExtmarkUndo);
 
 
-  changed_lines((linenr_T)start_row, 0, (linenr_T)end_row, (long)extra, true);
+  changed_lines((linenr_T)start_row, 0, (linenr_T)end_row + 1,
+                (long)extra, true);
 
   // adjust cursor like an extmark ( i e it was inside last_part_len)
   if (curwin->w_cursor.lnum == end_row && curwin->w_cursor.col > end_col) {

test/functional/api/buffer_spec.lua

@@ -513,6 +513,28 @@ describe('api/buf', function()
 	  eq({0, 8}, curbufmeths.get_extmark_by_id(ns, id2, {}))
 	  eq({0, 8}, curbufmeths.get_extmark_by_id(ns, id3, {}))
     end)
+
+    it("correctly marks changed region for redraw #13890", function()
+      local screen = Screen.new(20, 5)
+      screen:attach()
+
+      insert([[
+      AAA
+      BBB
+      ]])
+
+      curbufmeths.set_text(0, 0, 1, 3, {'XXX', 'YYY'})
+
+      screen:expect([[
+  XXX                 |
+  YYY                 |
+  ^                    |
+  ~                   |
+                      |
+
+      ]])
+
+    end)
   end)
 
   describe('nvim_buf_get_offset', function()