patch 9.0.1708: getcompletion() failes for user-defined commands

Problem: getcompletion() failes for user-defined commands
Solution: set context for completion function

closes: #12681
closes: #12680

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_cmdline.vim

@@ -3498,4 +3498,14 @@ func Test_rulerformat_position()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_usercmd_completion()
+  let g:complete=[]
+  command! -nargs=* -complete=command TestCompletion echo <q-args>
+  let g:complete = getcompletion('TestCompletion ', 'cmdline')
+  let a = getcompletion('', 'cmdline')
+
+  call assert_equal(a, g:complete)
+  delcom TestCompletion
+  unlet! g:complete
+endfunc
 " vim: shiftwidth=2 sts=2 expandtab

src/usercmd.c

@@ -329,7 +329,11 @@ set_context_in_user_cmdarg(
 	return set_context_in_menu_cmd(xp, cmd, arg, forceit);
 #endif
     if (context == EXPAND_COMMANDS)
+    {
+	if (xp->xp_context == EXPAND_NOTHING)
+	    xp->xp_context = context;
 	return arg;
+    }
     if (context == EXPAND_MAPPINGS)
 	return set_context_in_map_cmd(xp, (char_u *)"map", arg, forceit, FALSE,
 							FALSE, CMD_map);

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1708,
 /**/
     1707,
 /**/