vim-patch:9.1.1571: CmdlineChanged triggered to often

Problem:  The CmdlineChanged event was firing unnecessarily, even when
          the command line's content hadn't actually changed.

Solution: I've added a check to compare the command-line buffer's state
          before and after key processing. The `CmdlineChanged` event
          now only triggers if the buffer's contents are genuinely
          different (Girish Palya).

closes: vim/vim#17803

https://github.com/vim/vim/commit/239c4e4abe79c0f3611f0b4776ee34fbf0ac53cf

Co-authored-by: Girish Palya <girishji@gmail.com>

2 files changed, 66 insertions, 3 deletions

diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index eaee6c07a3..a156b83c7d 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -134,6 +134,7 @@ typedef struct {
   int save_msg_scroll;
   int save_State;                       // remember State when called
   int prev_cmdpos;
+  char *prev_cmdbuff;
   char *save_p_icm;
   bool some_key_typed;                  // one of the keys was typed
   // mouse drag and release events are ignored, unless they are
@@ -1013,12 +1014,14 @@ theend:
     ccline.cmdbuff = NULL;
   }
 
+  xfree(s->prev_cmdbuff);
   return (uint8_t *)p;
 }
 
 static int command_line_check(VimState *state)
 {
   CommandLineState *s = (CommandLineState *)state;
+  s->prev_cmdpos = ccline.cmdpos;
 
   redir_off = true;        // Don't redirect the typed command.
   // Repeated, because a ":redir" inside
@@ -1029,6 +1032,10 @@ static int command_line_check(VimState *state)
                            // that occurs while typing a command should
                            // cause the command not to be executed.
 
+  if (ccline.cmdbuff != NULL) {
+    s->prev_cmdbuff = xmemdupz(ccline.cmdbuff, (size_t)ccline.cmdpos);
+  }
+
   // Trigger SafeState if nothing is pending.
   may_trigger_safestate(s->xpc.xp_numfiles <= 0);
 
@@ -2288,7 +2295,6 @@ static void may_trigger_cursormovedc(CommandLineState *s)
 {
   if (ccline.cmdpos != s->prev_cmdpos) {
     trigger_cmd_autocmd(s->cmdline_type, EVENT_CURSORMOVEDC);
-    s->prev_cmdpos = ccline.cmdpos;
     ccline.redraw_state = MAX(ccline.redraw_state, kCmdRedrawPos);
   }
 }
@@ -2296,12 +2302,14 @@ static void may_trigger_cursormovedc(CommandLineState *s)
 static int command_line_not_changed(CommandLineState *s)
 {
   may_trigger_cursormovedc(s);
+  s->prev_cmdpos = ccline.cmdpos;
   // Incremental searches for "/" and "?":
   // Enter command_line_not_changed() when a character has been read but the
   // command line did not change. Then we only search and redraw if something
   // changed in the past.
   // Enter command_line_changed() when the command line did change.
   if (!s->is_state.incsearch_postponed) {
+    XFREE_CLEAR(s->prev_cmdbuff);
     return 1;
   }
   return command_line_changed(s);
@@ -2772,8 +2780,14 @@ static void do_autocmd_cmdlinechanged(int firstc)
 
 static int command_line_changed(CommandLineState *s)
 {
-  // Trigger CmdlineChanged autocommands.
-  do_autocmd_cmdlinechanged(s->firstc > 0 ? s->firstc : '-');
+  if (ccline.cmdpos != s->prev_cmdpos
+      || (s->prev_cmdbuff != NULL
+          && strncmp(s->prev_cmdbuff, ccline.cmdbuff, (size_t)s->prev_cmdpos) != 0)) {
+    // Trigger CmdlineChanged autocommands.
+    do_autocmd_cmdlinechanged(s->firstc > 0 ? s->firstc : '-');
+  }
+
+  XFREE_CLEAR(s->prev_cmdbuff);
 
   may_trigger_cursormovedc(s);
 
diff --git a/test/old/testdir/test_cmdline.vim b/test/old/testdir/test_cmdline.vim
index 3e8592a7d8..a49603311e 100644
--- a/test/old/testdir/test_cmdline.vim
+++ b/test/old/testdir/test_cmdline.vim
@@ -4719,4 +4719,53 @@ func Test_pum_scroll_noselect()
   call StopVimInTerminal(buf)
 endfunc
 
+" CmdlineChanged shouldn't trigger if command-line text is unchanged
+func Test_cmdline_changed()
+  let g:cmdchg_count = 0
+  let g:cmdprefix = ''
+  augroup test_CmdlineAugrp | autocmd!
+    autocmd CmdlineChanged * if getcmdline() =~ g:cmdprefix | let g:cmdchg_count += 1 | endif
+  augroup END
+
+  new
+  set wildmenu
+  set wildmode=full
+
+  let g:cmdprefix = 'echomsg'
+  let g:cmdchg_count = 0
+  call feedkeys(":echomsg\<Tab>", "tx")
+  call assert_equal(1, g:cmdchg_count) " once only for 'g', not again for <Tab>
+
+  let g:cmdchg_count = 0
+  let g:cmdprefix = 'echo'
+  call feedkeys(":ech\<Tab>", "tx")
+  call assert_equal(1, g:cmdchg_count) " (once for 'h' and) once for 'o'
+
+  set wildmode=noselect,full
+  let g:cmdchg_count = 0
+  let g:cmdprefix = 'ech'
+  call feedkeys(":ech\<Tab>", "tx")
+  call assert_equal(1, g:cmdchg_count) " once for 'h', not again for <tab>
+
+  command! -nargs=+ -complete=custom,TestComplete Test echo
+
+  func TestComplete(arglead, cmdline, cursorpos)
+    return "AbC"
+  endfunc
+
+  set wildoptions=fuzzy wildmode=full
+  let g:cmdchg_count = 0
+  let g:cmdprefix = 'Test \(AbC\|abc\)'
+  call feedkeys(":Test abc\<Tab>", "tx")
+  call assert_equal(2, g:cmdchg_count) " once for 'c', again for 'AbC'
+
+  bw!
+  set wildmode& wildmenu& wildoptions&
+  augroup test_CmdlineAugrp | autocmd! | augroup END
+  unlet g:cmdchg_count
+  unlet g:cmdprefix
+  delfunc TestComplete
+  delcommand Test
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab