The argument completion also has no extra options.

a748f513 · Carlo Dapor · Marc Cornellà · bd599066 · a748f513
Commit a748f513 authored Aug 12, 2016 by Carlo Dapor Committed by Marc Cornellà Sep 21, 2016
--- a/plugins/ng/ng.plugin.zsh
+++ b/plugins/ng/ng.plugin.zsh
@@ -16,7 +16,7 @@ _ng_completion () {
      opts='-o --output-path'
      ;;
-    i | install)
+    completion | i | install)
      opts=''
      ;;