overkill-nvim is a framework for building neovim plugins in Rust (not using msgpack!).

There are three crates that make up overkill-nvim:

• neovim-sys defines primitive types (ex. Object, Dictionary, etc) and FFI function signatures available in neovim that can be called.
• nvim-api wraps neovim-sys, providing a Rust API similar to neovim's Lua API.
• overkill-nvim uses nvim-api to provide a (opinionated) framework for writing plugins using richer types.

You can use nvim-api in a similar fashion to neovim's Lua API. For example, to set the signcolumn option to "yes:4", you could do:

use nvim_api::nvim;

#[no_mangle]
pub extern "C" fn set_my_options() {
    nvim::nvim_set_option("signcolumn", "yes:4").unwrap();
}

(You then need to make this callable in nvim; lua-jit or neovim's libcall work. More on this later.)

...but what if you fat-finger the option name or value? Well, in (neo)vim, you'd get an error message, telling you about your whoopsie, but since we're in Rust-land, you wouldn't get that error until you loaded your shared library into neovim and called set_my_options(). Sure would be nicer to know at compile time, yeah?

use overkill_nvim::option::{StringOption, SignColumn, SignColumnValue};

#[no_mangle]
pub extern "C" fn set_my_options() {
    SignColumn::set(SignColumnValue::YesWithMax(4)).unwrap();
}

(Again, this needs to be made callable in nvim)

And there you go--all type-checked at compile time.

Check out https://github.com/turboladen/init.rs for more.

Well, for neovim-sys and nvim-api, the goals are simply to provide a Rust interface to neovim that's not over msgpack. Nothing against msgpack, but doesn't the idea of calling neovim directly instead of through that extra layer sound a bit nicer?

As for overkill-nvim, well, it's probably overkill, but I really like to have types to tell me what I can and can't do--overkill-nvim give me a typed interface over neovim functionality that guide me into doing the right thing.

Inspiration came from this post on the neovim discourse. The Rust crates are built without the neovim symbols actually available at compile time. You build a shared library using nvim-api or overkill-nvim, then either:

• Use neovim's libcall or libcallnr to load the library and call a single function from it, or...
• Use lua-jit's ffi module for a) defining your FFI symbols, and b) loading the library. The specs in tests/plenary do this to be able to test these crates in neovim.

It's quite possible to have your Rust library make all the neovim calls that you need want, and would thus leave you only needing to define a simple function to call from neovim that kicks off all of your calls via Rust.