lua-rs-runtime

Embed Lua 5.4 in a Rust program. lua-rs-runtime is the embedding API for lua-rs, a Lua 5.4 implementation written in safe Rust. Because the whole runtime is Rust, it embeds where a C binding can't: wasm32-unknown-unknown, no C toolchain, no liblua to link. You give up LuaJIT speed and years of maturity in exchange.

[dependencies]
lua-rs-runtime = "0.0.11"

Calling Rust from Lua

use lua_rs_runtime::{Lua, Result};

fn main() -> Result<()> {
    let lua = Lua::new();
    let f = lua.create_function(|_, name: String| Ok(format!("hello, {name}")))?;
    lua.globals().set("greet", f)?;

    let out: String = lua.load(r#"return greet("lua-rs")"#).eval()?;
    assert_eq!(out, "hello, lua-rs");
    Ok(())
}

The API is shaped after mlua: owned GC-rooted handles (Value, Table, Function, AnyUserData), closure callbacks, conversion traits, and UserData for binding Rust types with methods, fields, and metamethods. A #[derive(LuaUserData)] / #[lua_methods] macro pair generates the boilerplate.

Scope: lending non-'static borrows

Lua::scope lends Lua a value that lives on the Rust stack for one call (the classic case is a game engine's &mut World). The borrow is invalidated when the scope returns, so a script that stashes a handle and uses it later gets a clean Lua error instead of touching freed memory.

lua.scope(|s| {
    let world = s.create_userdata_ref_mut(&lua, &mut my_world)?;
    lua.globals().set("world", &world)?;
    lua.load("world:spawn('player')").exec()
})?;

Scope::create_function does the same for closures that capture non-'static borrows, and AnyUserData::delegate returns a sub-userdata that re-borrows a field of its parent per call, so an App -> World -> Component chain stays a chain of short borrows. Runnable example: cargo run -p lua-rs-runtime --example scope_world.

Links

• Worked Bevy 0.18 integration, native and in the browser: bevy-lua-rs-starter (live demo).
• WebAssembly distribution: lua-rs-wasm.
• Project, benchmarks, and conformance: github.com/ianm199/lua-rs.

License

A port of Lua (PUC-Rio). MIT-licensed.