vim-patch:8.2.3629: command completion in cmdline window uses global commands

Problem:    Command completion in cmdline window uses global user commands,
            not local commands for the window where it was opened from.
Solution:   Use local commands. (closes vim/vim#9168)
a119812437

src/nvim/eval.c

@@ -3218,9 +3218,8 @@ char_u *get_user_var_name(expand_T *xp, int idx)
 
   // b: variables
   // In cmdwin, the alternative buffer should be used.
-  hashtab_T *ht = (cmdwin_type != 0 && get_cmdline_type() == NUL)
-    ? &prevwin->w_buffer->b_vars->dv_hashtab
-    : &curbuf->b_vars->dv_hashtab;
+  hashtab_T *ht
+      = is_in_cmdwin() ? &prevwin->w_buffer->b_vars->dv_hashtab : &curbuf->b_vars->dv_hashtab;
   if (bdone < ht->ht_used) {
     if (bdone++ == 0) {
       hi = ht->ht_array;
@@ -3235,9 +3234,7 @@ char_u *get_user_var_name(expand_T *xp, int idx)
 
   // w: variables
   // In cmdwin, the alternative window should be used.
-  ht = (cmdwin_type != 0 && get_cmdline_type() == NUL)
-    ? &prevwin->w_vars->dv_hashtab
-    : &curwin->w_vars->dv_hashtab;
+  ht = is_in_cmdwin() ? &prevwin->w_vars->dv_hashtab : &curwin->w_vars->dv_hashtab;
   if (wdone < ht->ht_used) {
     if (wdone++ == 0) {
       hi = ht->ht_array;

src/nvim/ex_docmd.c

@@ -2701,10 +2701,8 @@ static char_u *find_ucmd(exarg_T *eap, char_u *p, int *full, expand_T *xp, int *
   bool amb_local = false;            // Found ambiguous buffer-local command,
                                      // only full match global is accepted.
 
-  /*
-   * Look for buffer-local user commands first, then global ones.
-   */
-  gap = &curbuf->b_ucmds;
+  // Look for buffer-local user commands first, then global ones.
+  gap = is_in_cmdwin() ? &prevwin->w_buffer->b_ucmds : &curbuf->b_ucmds;
   for (;;) {
     for (j = 0; j < gap->ga_len; j++) {
       uc = USER_CMD_GA(gap, j);
@@ -5351,9 +5349,7 @@ static void uc_list(char_u *name, size_t name_len)
   uint32_t a;
 
   // 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;
+  garray_T *gap = is_in_cmdwin() ? &prevwin->w_buffer->b_ucmds : &curbuf->b_ucmds;
   for (;;) {
     for (i = 0; i < gap->ga_len; i++) {
       cmd = USER_CMD_GA(gap, i);
@@ -6307,9 +6303,7 @@ char_u *get_user_commands(expand_T *xp FUNC_ATTR_UNUSED, int idx)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
   // In cmdwin, the alternative buffer should be used.
-  const buf_T *const buf = (cmdwin_type != 0 && get_cmdline_type() == NUL)
-    ? prevwin->w_buffer
-    : curbuf;
+  const buf_T *const buf = is_in_cmdwin() ? prevwin->w_buffer : curbuf;
 
   if (idx < buf->b_ucmds.ga_len) {
     return USER_CMD_GA(&buf->b_ucmds, idx)->uc_name;
@@ -6331,7 +6325,7 @@ static char_u *get_user_command_name(int idx, int cmdidx)
   }
   if (cmdidx == CMD_USER_BUF) {
     // In cmdwin, the alternative buffer should be used.
-    buf_T *buf = (cmdwin_type != 0 && get_cmdline_type() == NUL) ? prevwin->w_buffer : curbuf;
+    buf_T *buf = is_in_cmdwin() ? prevwin->w_buffer : curbuf;
     if (idx < buf->b_ucmds.ga_len) {
       return USER_CMD_GA(&buf->b_ucmds, idx)->uc_name;
     }

src/nvim/ex_getln.c

@@ -6587,6 +6587,13 @@ static int open_cmdwin(void)
   return cmdwin_result;
 }
 
+/// @return true if in the cmdwin, not editing the command line.
+bool is_in_cmdwin(void)
+  FUNC_ATTR_PURE
+{
+  return cmdwin_type != 0 && get_cmdline_type() == NUL;
+}
+
 /// Get script string
 ///
 /// Used for commands which accept either `:command script` or

src/nvim/testdir/test_ins_complete.vim

@@ -341,6 +341,14 @@ func Test_compl_feedkeys()
   set completeopt&
 endfunc
 
+func s:ComplInCmdwin_GlobalCompletion(a, l, p)
+  return 'global'
+endfunc
+
+func s:ComplInCmdwin_LocalCompletion(a, l, p)
+  return 'local'
+endfunc
+
 func Test_compl_in_cmdwin()
   set wildmenu wildchar=<Tab>
   com! -nargs=1 -complete=command GetInput let input = <q-args>
@@ -376,6 +384,47 @@ func Test_compl_in_cmdwin()
   call feedkeys("q::GetInput b:test_\<Tab>\<CR>:q\<CR>", 'tx!')
   call assert_equal('b:test_', input)
 
+
+  " Argument completion of buffer-local command
+  func s:ComplInCmdwin_GlobalCompletionList(a, l, p)
+    return ['global']
+  endfunc
+
+  func s:ComplInCmdwin_LocalCompletionList(a, l, p)
+    return ['local']
+  endfunc
+
+  func s:ComplInCmdwin_CheckCompletion(arg)
+    call assert_equal('local', a:arg)
+  endfunc
+
+  com! -nargs=1 -complete=custom,<SID>ComplInCmdwin_GlobalCompletion
+       \ TestCommand call s:ComplInCmdwin_CheckCompletion(<q-args>)
+  com! -buffer -nargs=1 -complete=custom,<SID>ComplInCmdwin_LocalCompletion
+       \ TestCommand call s:ComplInCmdwin_CheckCompletion(<q-args>)
+  call feedkeys("q:iTestCommand \<Tab>\<CR>", 'tx!')
+
+  com! -nargs=1 -complete=customlist,<SID>ComplInCmdwin_GlobalCompletionList
+       \ TestCommand call s:ComplInCmdwin_CheckCompletion(<q-args>)
+  com! -buffer -nargs=1 -complete=customlist,<SID>ComplInCmdwin_LocalCompletionList
+       \ TestCommand call s:ComplInCmdwin_CheckCompletion(<q-args>)
+
+  call feedkeys("q:iTestCommand \<Tab>\<CR>", 'tx!')
+
+  func! s:ComplInCmdwin_CheckCompletion(arg)
+    call assert_equal('global', a:arg)
+  endfunc
+  new
+  call feedkeys("q:iTestCommand \<Tab>\<CR>", 'tx!')
+  quit
+
+  delfunc s:ComplInCmdwin_GlobalCompletion
+  delfunc s:ComplInCmdwin_LocalCompletion
+  delfunc s:ComplInCmdwin_GlobalCompletionList
+  delfunc s:ComplInCmdwin_LocalCompletionList
+  delfunc s:ComplInCmdwin_CheckCompletion
+
+  delcom -buffer TestCommand
   delcom TestCommand
   delcom GetInput
   unlet w:test_winvar