fix(buffer_updates): handle :sort of already sorted buffer

2 files changed, 20 insertions, 4 deletions

diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index bbc1dd9717..3bfbb42d87 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -702,11 +702,11 @@ void ex_sort(exarg_T *eap)
     mark_adjust(eap->line2, MAXLNUM, -deleted, 0L, kExtmarkNOOP);
   }
 
-  extmark_splice(curbuf, eap->line1-1, 0,
-                 count, 0, old_count,
-                 lnum - eap->line2, 0, new_count, kExtmarkUndo);
-
   if (change_occurred || deleted != 0) {
+    extmark_splice(curbuf, eap->line1-1, 0,
+                   count, 0, old_count,
+                   lnum - eap->line2, 0, new_count, kExtmarkUndo);
+
     changed_lines(eap->line1, 0, eap->line2 + 1, -deleted, true);
   }
 
diff --git a/test/functional/lua/buffer_updates_spec.lua b/test/functional/lua/buffer_updates_spec.lua
index 83ed7394b0..c83a50b78b 100644
--- a/test/functional/lua/buffer_updates_spec.lua
+++ b/test/functional/lua/buffer_updates_spec.lua
@@ -1088,6 +1088,22 @@ describe('lua: nvim_buf_attach on_bytes', function()
       }
     end)
 
+    it(":sort lines", function()
+      local check_events = setup_eventcheck(verify, {"CCC", "BBB", "AAA"})
+
+      command "%sort"
+      check_events {
+        { "test1", "bytes", 1, 3, 0, 0, 0, 3, 0, 12, 3, 0, 12 };
+      }
+    end)
+
+    it("handles already sorted lines", function()
+      local check_events = setup_eventcheck(verify, {"AAA", "BBB", "CCC"})
+
+      command "%sort"
+      check_events { }
+    end)
+
     local function test_lockmarks(mode)
       local description = (mode ~= "") and mode or "(baseline)"
       it("test_lockmarks " .. description .. " %delete _", function()