vim-patch:8.1.1732: completion in cmdwin does not work for buffer-local commands

Problem:    Completion in cmdwin does not work for buffer-local commands.
Solution:   Use the right buffer. (closes vim/vim#4711)
https://github.com/vim/vim/commit/f03e328348f87e1fe8ce4aad2a6a4237b9f78ce3

2 files changed, 35 insertions, 7 deletions

diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 641edf4610..f18ebffa0a 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -5133,9 +5133,11 @@ static void uc_list(char_u *name, size_t name_len)
   ucmd_T      *cmd;
   int len;
   uint32_t a;
-  garray_T    *gap;
 
-  gap = &curbuf->b_ucmds;
+  // In cmdwin, the alternative buffer should be used.
+  garray_T *gap = (cmdwin_type != 0 && get_cmdline_type() == NUL)
+    ? &prevwin->w_buffer->b_ucmds
+    : &curbuf->b_ucmds;
   for (;; ) {
     for (i = 0; i < gap->ga_len; ++i) {
       cmd = USER_CMD_GA(gap, i);
@@ -5984,13 +5986,21 @@ char_u *get_user_cmd_addr_type(expand_T *xp, int idx)
 /*
  * Function given to ExpandGeneric() to obtain the list of user command names.
  */
-char_u *get_user_commands(expand_T *xp, int idx)
+char_u *get_user_commands(expand_T *xp FUNC_ATTR_UNUSED, int idx)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  if (idx < curbuf->b_ucmds.ga_len)
-    return USER_CMD_GA(&curbuf->b_ucmds, idx)->uc_name;
-  idx -= curbuf->b_ucmds.ga_len;
-  if (idx < ucmds.ga_len)
+  // In cmdwin, the alternative buffer should be used.
+  const buf_T *const buf = (cmdwin_type != 0 && get_cmdline_type() == NUL)
+    ? prevwin->w_buffer
+    : curbuf;
+
+  if (idx < buf->b_ucmds.ga_len) {
+    return USER_CMD_GA(&buf->b_ucmds, idx)->uc_name;
+  }
+  idx -= buf->b_ucmds.ga_len;
+  if (idx < ucmds.ga_len) {
     return USER_CMD(idx)->uc_name;
+  }
   return NULL;
 }
 
diff --git a/src/nvim/testdir/test_ins_complete.vim b/src/nvim/testdir/test_ins_complete.vim
index 7f52481ba8..52ec281d82 100644
--- a/src/nvim/testdir/test_ins_complete.vim
+++ b/src/nvim/testdir/test_ins_complete.vim
@@ -285,3 +285,21 @@ func Test_compl_feedkeys()
   bwipe!
   set completeopt&
 endfunc
+
+func Test_compl_in_cmdwin()
+  set wildmenu wildchar=<Tab>
+  com! -nargs=1 -complete=command GetInput let input = <q-args>
+  com! -buffer TestCommand echo 'TestCommand'
+
+  let input = ''
+  call feedkeys("q:iGetInput T\<C-x>\<C-v>\<CR>", 'tx!')
+  call assert_equal('TestCommand', input)
+
+  let input = ''
+  call feedkeys("q::GetInput T\<Tab>\<CR>:q\<CR>", 'tx!')
+  call assert_equal('T', input)
+
+  delcom TestCommand
+  delcom GetInput
+  set wildmenu& wildchar&
+endfunc