From c6c348471d0ee4b87188c62bb7cc918d84dbd654 Mon Sep 17 00:00:00 2001
From: luukvbaal <luukvbaal@gmail.com>
Date: Mon, 6 Apr 2026 19:15:46 +0200
Subject: [PATCH] fix(cmdline): 'inccommand' preview after setcmdline() #38795

Problem:  'inccommand' preview is not executed after setcmdline(),
          and as a result cmdline_show event is emitted when redrawing
          is not allowed (5b6477be).
Solution: Call command_line_changed() when ccline.cmdbuff_replaced is
          set (by setcmdline()).
(cherry picked from commit 135478702985f470a3d503f197a7f57c17d962a3)
---
 src/nvim/ex_getln.c                  |  9 +++++++--
 test/functional/ui/cmdline2_spec.lua | 26 ++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 05d424ceb2..5a355ffe1c 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -1324,6 +1324,10 @@ static int command_line_execute(VimState *state, int key)
     if (display_tick > display_tick_saved && s->is_state.did_incsearch) {
       may_do_incsearch_highlighting(s->firstc, s->count, &s->is_state);
     }
+    // If f_setcmdline() changed the cmdline treat it as such.
+    if (ccline.cmdbuff_replaced) {
+      command_line_changed(s);
+    }
 
     // nvim_select_popupmenu_item() can be called from the handling of
     // K_EVENT, K_COMMAND, or K_LUA.
@@ -2893,8 +2897,9 @@ static int command_line_changed(CommandLineState *s)
     }
   }
 
-  if (ccline.cmdpos != s->prev_cmdpos
-      || (s->prev_cmdbuff != NULL && strcmp(s->prev_cmdbuff, ccline.cmdbuff) != 0)) {
+  if (!ccline.cmdbuff_replaced
+      && (ccline.cmdpos != s->prev_cmdpos
+          || (s->prev_cmdbuff != NULL && strcmp(s->prev_cmdbuff, ccline.cmdbuff) != 0))) {
     // Trigger CmdlineChanged autocommands.
     do_autocmd_cmdlinechanged(s->firstc > 0 ? s->firstc : '-');
   }
diff --git a/test/functional/ui/cmdline2_spec.lua b/test/functional/ui/cmdline2_spec.lua
index 402700c88d..00d56fd504 100644
--- a/test/functional/ui/cmdline2_spec.lua
+++ b/test/functional/ui/cmdline2_spec.lua
@@ -237,6 +237,32 @@ describe('cmdline2', function()
       {16::}{15:call} {25:Foo}{16:()}^                                          |
     ]])
   end)
+
+  it('updated after setcmdline() #38764', function()
+    -- Also check that command-preview is updated.
+    exec('call setline(1, "foo")')
+    feed(':%s/foo')
+    screen:expect([[
+      {10:foo}                                                  |
+      {1:~                                                    }|*12
+      {16::}%{15:s}{16:/foo^ }                                             |
+    ]])
+    exec_lua(function()
+      _G.events = {}
+      vim.api.nvim_create_autocmd({ 'CmdlineChanged', 'CursorMovedC' }, {
+        callback = function(ev)
+          _G.events[ev.event] = (_G.events[ev.event] or 0) + 1
+        end,
+      })
+    end)
+    exec('call setcmdline("%s/fo")')
+    screen:expect([[
+      {10:fo}o                                                  |
+      {1:~                                                    }|*12
+      {16::}%{15:s}{16:/fo^ }                                              |
+    ]])
+    t.eq({ CmdlineChanged = 1, CursorMovedC = 1 }, exec_lua('return _G.events'))
+  end)
 end)
 
 describe('cmdline2', function()