From 756e55dc490d98f9ec09885bb6261e8160ebf914 Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Tue, 30 Sep 2025 09:11:07 +0800
Subject: [PATCH] vim-patch:9.1.1810: completion: "longest" doesn't work for
 manual completion with 'ac'

Problem:  completion: "longest" doesn't work for manual completion when
          'autocomplete' is on (after 9.1.1800).
Solution: Only reset compl_get_longest when enabling autocompletion
          (zeertzjq).

closes: vim/vim#18430

https://github.com/vim/vim/commit/b3966d6a8e96c9de45a344ec3d42fbb156863835
---
 src/nvim/insexpand.c                   | 10 +++++++---
 test/old/testdir/test_ins_complete.vim | 17 ++++++++++++++++-
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
index aed25df3b9..1a94684951 100644
--- a/src/nvim/insexpand.c
+++ b/src/nvim/insexpand.c
@@ -2266,7 +2266,11 @@ static void ins_compl_new_leader(void)
     // Matches were cleared, need to search for them now.
     // Set "compl_restarting" to avoid that the first match is inserted.
     compl_restarting = true;
-    compl_autocomplete = ins_compl_has_autocomplete();
+    if (ins_compl_has_autocomplete()) {
+      ins_compl_enable_autocomplete();
+    } else {
+      compl_autocomplete = false;
+    }
     if (ins_complete(Ctrl_N, true) == FAIL) {
       compl_cont_status = 0;
     }
@@ -2736,8 +2740,7 @@ bool ins_compl_prep(int c)
   // Set "compl_get_longest" when finding the first matches.
   if (ctrl_x_mode_not_defined_yet()
       || (ctrl_x_mode_normal() && !compl_started)) {
-    compl_get_longest = (get_cot_flags() & kOptCotFlagLongest) != 0
-                        && !ins_compl_has_autocomplete();
+    compl_get_longest = (get_cot_flags() & kOptCotFlagLongest) != 0;
     compl_used_match = true;
   }
 
@@ -6293,6 +6296,7 @@ int ins_complete(int c, bool enable_pum)
 void ins_compl_enable_autocomplete(void)
 {
   compl_autocomplete = true;
+  compl_get_longest = false;
 }
 
 /// Remove (if needed) and show the popup menu
diff --git a/test/old/testdir/test_ins_complete.vim b/test/old/testdir/test_ins_complete.vim
index d362c6ed83..e34e39bd3e 100644
--- a/test/old/testdir/test_ins_complete.vim
+++ b/test/old/testdir/test_ins_complete.vim
@@ -5984,7 +5984,7 @@ func Test_autocomplete_longest()
   call feedkeys("Go\<ESC>", 'tx')
   call DoTest("f\<C-N>\<C-N>\<BS>\<BS>\<BS>\<BS>", 'foo', 3)
 
-  " Issue #18410: When both 'preinsert' and 'longest' are set, 'preinsert'
+  " Issue #18410: When both "preinsert" and "longest" are set, "preinsert"
   " takes precedence
   %delete
   set autocomplete completeopt+=longest,preinsert
@@ -6035,6 +6035,21 @@ func Test_autocomplete_longest()
   %delete _
   delfunc CheckUndo
 
+  " Check that behavior of "longest" in manual completion is unchanged.
+  for ac in [v:false, v:true]
+    let &ac = ac
+    set completeopt=menuone,longest
+    call feedkeys("Ssign u\<C-X>\<C-V>", 'tx')
+    call assert_equal('sign un', getline('.'))
+    call feedkeys("Ssign u\<C-X>\<C-V>\<C-V>", 'tx')
+    call assert_equal('sign undefine', getline('.'))
+    call feedkeys("Ssign u\<C-X>\<C-V>\<C-V>\<C-V>", 'tx')
+    call assert_equal('sign unplace', getline('.'))
+    call feedkeys("Ssign u\<C-X>\<C-V>\<C-V>\<C-V>\<C-V>", 'tx')
+    call assert_equal('sign u', getline('.'))
+    %delete
+  endfor
+
   bw!
   set cot& autocomplete&
   delfunc GetLine