This is not a breaking change. Everything that works on Vim8 script will continue to work. The new scripting language will provide extensions that you can use to get better speed.
> I would have loved for Vim to also adopt Lua
Vim has supported Lua for a long time. Anyone who wants to really use Lua for Vim plugins already has the option of doing so.
> Vim has supported Lua for a long time. Anyone who wants to really use Lua for Vim plugins already has the option of doing so.
How does that compare to writing Lua plugins for Neovim? Seemingly all search results for "write vim plugin in lua" are dominated by results for writing lua plugins for neovim. Does vanilla Vim have something like Neovim's "Remote Plugin" or how does it work?
My understanding is that neovim devs would like to see a lua interface in vim, but right now there's a lot of functions in neovim's lua interface that are not available in vim's lua interface.
But for the stuff that is available, you can either use the vim help to learn about it or search on vim's github issues / PRs, e.g. https://github.com/vim/vim/pull/7959. I'm curious if there are other ways to learn more about vim's lua interface, searching on google as you said does not give great results for vim, just neovim.
I do question if a breaking change for a custom language is the right way to go.
Built in Lua support in Neovim (with LuaJIT) has done wonders for the plugin ecosystem.
There is a lot of activity, and a lot of pluings with great quality have quickly replaced older ones.
That's no surprise. LuaJIT is fast, much easier to write, has a has a sizeable ecosystem and a good LSP server.
Even an overhauled Vimscript won't be anything more than a odd niche language with worse performance.
I would have loved for Vim to also adopt Lua and the Lua API from Neovim to prevent a complete ecosystem split.
I just don't see how implementing a new language makes sense in this context, except for fun.