nvim-langserver-shim internally uses an older version of https://github.com/prabirshrestha/vim-lsp
I'm hoping in couple of weeks vim-lsp will be stable and so that I can start contributing to nvim-langserver-shim. Currently I'm developing vim-lsp independently.
It already works asynchronously in neovim and vim on windows, mac and linux. You can follow up with the discussion at https://github.com/neovim/neovim/issues/5522 (you can see some of the progress in thread in gifs)
As someone who had worked on language support in IDEs for the past 5 years, it's really great that we have finally arrived to the point of getting common protocols. IDEs have historically been very self-contained, each with its own ecosystem, resulting in a lot of unnecessary duplication of effort. Now, at last, we can do neat things that are immediately usable across the entire language ecosystem at once.
Better yet, we can have language designers implement support themselves, ideally using the same code that powers their compiler. Historically, tooling support has been the single biggest stumbling block for new languages, no matter how promising. This should significantly reduce the barrier to entry for that, and make new languages more viable as a result.
The fact that it can also be used to "light up" hardcore editors like Vim and Emacs is also a nice bonus!
YouCompleteMe for vim, although it relies on python so may not be portable. I took a quick stab at building one in pure vimscript and a process in vim 8 and it seemed very doable.
