From fcf752476a33a26058b3342ac09108f76801bd4b Mon Sep 17 00:00:00 2001
From: glepnir <glephunter@gmail.com>
Date: Sun, 28 Sep 2025 11:28:05 +0800
Subject: [PATCH] fix(cmd): :update writes new file buffers only for real files
 #35939

Problem: :update should write new file buffers, but previous fix
affected special buffer types (acwrite, nofile, etc.).

Solution: Add bt_nofilename() check to only write new files for
buffers representing real filesystem paths.
---
 runtime/doc/editing.txt                |  3 ++-
 runtime/doc/vim_diff.txt               |  1 +
 src/nvim/ex_cmds.c                     |  4 +++-
 test/functional/ex_cmds/write_spec.lua | 11 +++++++++++
 4 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/runtime/doc/editing.txt b/runtime/doc/editing.txt
index 7d1798c34e..cb5de0f2e5 100644
--- a/runtime/doc/editing.txt
+++ b/runtime/doc/editing.txt
@@ -989,7 +989,8 @@ slower (but safer).
 							*:up* *:update*
 :[range]up[date][!] [++opt] [>>] [file]
 			Like ":write", but only write when the buffer has been
-			modified.
+			modified, or when the buffer represents a new file
+			that doesn't exist on disk.
 
 
 WRITING WITH MULTIPLE BUFFERS				*buffer-write*
diff --git a/runtime/doc/vim_diff.txt b/runtime/doc/vim_diff.txt
index d0c24e296a..470378d87e 100644
--- a/runtime/doc/vim_diff.txt
+++ b/runtime/doc/vim_diff.txt
@@ -308,6 +308,7 @@ Commands:
 - |:trust|
 - User commands can support |:command-preview| to show results as you type
 - |:write| with "++p" flag creates parent directories.
+- |:update| command writes new file buffers even when unmodified.
 
 Editor:
 - |prompt-buffer| supports multiline input/paste, undo/redo, and o/O normal
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index e2c918a0e3..e28f282dc4 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -1772,7 +1772,9 @@ void ex_file(exarg_T *eap)
 /// ":update".
 void ex_update(exarg_T *eap)
 {
-  if (curbufIsChanged() || (curbuf->b_ffname != NULL && !os_path_exists(curbuf->b_ffname))) {
+  if (curbufIsChanged()
+      || (!bt_nofilename(curbuf) && curbuf->b_ffname != NULL
+          && !os_path_exists(curbuf->b_ffname))) {
     do_write(eap);
   }
 }
diff --git a/test/functional/ex_cmds/write_spec.lua b/test/functional/ex_cmds/write_spec.lua
index 15055175e7..668fc3ecf4 100644
--- a/test/functional/ex_cmds/write_spec.lua
+++ b/test/functional/ex_cmds/write_spec.lua
@@ -258,4 +258,15 @@ describe(':update', function()
     eq(1, eval('g:write_pre'))
     eq(1, eval('g:write_post'))
   end)
+
+  it('does not write acwrite buffer when unchanged', function()
+    command('file remote://test')
+    command('setlocal buftype=acwrite')
+    command('let g:triggered = 0 | autocmd BufWriteCmd remote://* let g:triggered = 1')
+    command('update')
+    eq(0, eval('g:triggered'))
+    command('call setline(1, ["hello"])')
+    command('update')
+    eq(1, eval('g:triggered'))
+  end)
 end)