vim-patch:8.2.1054: not so easy to pass a lua function to Vim
vim-patch:8.2.1084: Lua: registering function has useless code
I think I have also opened up the possibility for people to use these
callbacks elsewhere, since I've added a new struct that we should be
able to use.
Also, this should allow us to determine what the state of a list is in
Lua or a dictionary in Lua, since we now can track the luaref as we go.
- Return VimL errors instead of generic errors for:
- nvim_call_function
- nvim_call_dict_function
- Fix tests which were silently broken before this change.
This violates #6150 where we agreed not to translate API errors. But
that can be fixed later.
