From b54e57ee54f0a4e6eac74b071071a9d85326de3a Mon Sep 17 00:00:00 2001
From: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Date: Thu, 21 May 2026 19:57:06 +0000
Subject: [PATCH] patch 9.2.0508: completion: cannot complete user cmd :K with
 'ignorecase'

Problem:  completion: cannot complete user cmd :K with 'ignorecase'
          (rendcrx)
Solution: Skip the short-circuit when 'ignorecase' is set
          (Yasuhiro Matsumoto)

The set_cmd_index() short-circuit for the :k command treats ":k<X>" as
":k {X}" (mark argument), which makes ":kz<Tab>" never reach the
command-name expansion path. With 'ignorecase' the same prefix on other
letters (":gz<Tab>") completes a user command like :Gz, so the result is
inconsistent. Skip the short-circuit when 'ignorecase' is set; default
behaviour is preserved so the existing :k tests still pass.

fixes:  #20241
closes: #20275

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/cmdexpand.c              |  9 +++++----
 src/testdir/test_cmdline.vim | 21 +++++++++++++++++++++
 src/version.c                |  2 ++
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index 19ae319981..8d9c2d7b7f 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -1759,11 +1759,12 @@ set_cmd_index(char_u *cmd, exarg_T *eap, expand_T *xp, int *complp)
     // Isolate the command and search for it in the command table.
     // Exceptions:
     // - the 'k' command can directly be followed by any character, but do
-    // accept "keepmarks", "keepalt" and "keepjumps". As fuzzy matching can
-    // find matches anywhere in the command name, do this only for command
-    // expansion based on regular expression and not for fuzzy matching.
+    // accept "keepmarks", "keepalt" and "keepjumps". Bypass also when
+    // 'ignorecase' is set so a lowercase ":kz" still completes a user
+    // command like :Kz (#20241), and for fuzzy matching as that can find
+    // matches anywhere in the command name.
     // - the 's' command can be followed directly by 'c', 'g', 'i', 'I' or 'r'
-    if (!fuzzy && (*cmd == 'k' && cmd[1] != 'e'))
+    if (!fuzzy && !p_ic && (*cmd == 'k' && cmd[1] != 'e'))
     {
 	eap->cmdidx = CMD_k;
 	p = cmd + 1;
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 7c1365b6a9..31fb1f8ffc 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -4095,6 +4095,27 @@ func Test_fuzzy_completion_cmd_k()
   set wildoptions&
 endfunc
 
+" Issue #20241: with 'ignorecase', a lowercase "k"-prefixed input should
+" still complete a user command starting with "K".
+func Test_cmdline_complete_user_cmd_k_with_ignorecase()
+  command! Kz echo "hello"
+  command! Gz echo "here"
+
+  set noignorecase
+  call assert_equal([], getcompletion('kz', 'cmdline'))
+  call assert_equal([], getcompletion('gz', 'cmdline'))
+  call assert_equal(['Kz'], getcompletion('Kz', 'cmdline'))
+  call assert_equal(['Gz'], getcompletion('Gz', 'cmdline'))
+
+  set ignorecase
+  call assert_equal(['Kz'], getcompletion('kz', 'cmdline'))
+  call assert_equal(['Gz'], getcompletion('gz', 'cmdline'))
+
+  set ignorecase&
+  delcommand Kz
+  delcommand Gz
+endfunc
+
 " Test for fuzzy completion for user defined custom completion function
 func Test_fuzzy_completion_custom_func()
   func Tcompl(a, c, p)
diff --git a/src/version.c b/src/version.c
index 863043dabd..40b26d7cfe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    508,
 /**/
     507,
 /**/