From aa7cba995dc0ba55de8886d12f1a7f37715bea6e Mon Sep 17 00:00:00 2001
From: glepnir <glephunter@gmail.com>
Date: Tue, 14 Apr 2026 14:30:16 +0800
Subject: [PATCH] fix(completion): preselect ignores completeopt flag #39030

Problem: compl_preselect_match is set even when completeopt doesn't
include preselect.

Solution: Check kOptCotFlagPreselect in ins_compl_add before setting
compl_preselect_match.
---
 src/nvim/insexpand.c                       | 10 ++++++++--
 test/functional/editor/completion_spec.lua |  6 ++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
index 83af30d6e4..17d7c9e4be 100644
--- a/src/nvim/insexpand.c
+++ b/src/nvim/insexpand.c
@@ -971,7 +971,8 @@ static int ins_compl_add(char *const str, int len, char *const fname, char *cons
   match->cp_number = flags & CP_ORIGINAL_TEXT ? 0 : -1;
   match->cp_str = cbuf_to_string(str, (size_t)len);
   match->cp_preselect = preselect;
-  if (preselect && compl_preselect_match == NULL) {
+  if (preselect && compl_preselect_match == NULL
+      && (get_cot_flags() & kOptCotFlagPreselect)) {
     compl_preselect_match = match;
   }
 
@@ -3452,7 +3453,7 @@ static void set_completion(colnr_T startcol, list_T *list)
 
   compl_curr_match = compl_first_match;
   bool no_select = compl_no_select || compl_longest;
-  if ((get_cot_flags() & kOptCotFlagPreselect) && compl_preselect_match && !no_select) {
+  if (compl_preselect_match && !no_select) {
     compl_curr_match = compl_preselect_match->cp_prev;
     ins_complete(Ctrl_N, false);
   } else if (compl_no_insert || no_select) {
@@ -6511,6 +6512,11 @@ static void remove_old_matches(void)
         shown_match_removed = true;
       }
 
+      // Avoid dangling pointer when preselect match is removed.
+      if (to_delete == compl_preselect_match) {
+        compl_preselect_match = NULL;
+      }
+
       current = current->cp_next;
 
       if (to_delete == compl_first_match) {  // node to remove is at head
diff --git a/test/functional/editor/completion_spec.lua b/test/functional/editor/completion_spec.lua
index d873ec67cf..acadf16c9b 100644
--- a/test/functional/editor/completion_spec.lua
+++ b/test/functional/editor/completion_spec.lua
@@ -328,6 +328,12 @@ describe('completion', function()
           {1:~                                                           }|*2
           {5:-- INSERT --}                                                |
         ]])
+
+        -- without "preselect" in completeopt, preselect attribute is ignored
+        feed('<Esc>S')
+        command('set completeopt-=preselect')
+        feed('<C-r>=TestComplete()<CR><C-N><C-Y>')
+        eq('aaa', api.nvim_get_current_line())
       end)
     end)
   end)