Porting large code base -> luaL_opt* + working with the stack from rust

[bobbens]

Hello, thanks for the great project.
I'm porting a large C+Lua code base to rust, and I'm wondering if there are any macros or tricks to deal with things like luaL_optnumber to help simplify making the bindings. Using match + throwing an error seems to be a lot more work. In particular, something that would be a luaL_optnumber becomes something like:

                let n = match val {
                    Value::Number(n) => n,
                    Value::Nil => 1.,
                    _ => {
                        return Err(mlua::Error::BadArgument {
                            to: Some(String::from("number | nil")),
                            pos: 2,
                            name: Some(String::from("n")),
                            cause: Arc::new(mlua::Error::UserDataTypeMismatch),
                        })
                    }
                };

which is a bit more than the one-liner it is in C...

Also, C and rust are going to have to co-exist for a while. Is there any way to deal with Lua stack indices with mlua or do I have to resort to using the C API?

[khvzak]

luaL_optnumber and other helper functions should not be needed ideally.
You can declare types in your Rust function and mlua will take care of generating errors when args are wrong.
E.g. luaL_optnumber is Option<f64> in Rust:

let func = lua.create_function(|_lua, arg: Option<f32>| {
    dbg!(arg);
    Ok(arg)
})?;

Is there any way to deal with Lua stack indices with mlua or do I have to resort to using the C API?

You could try Lua::exec_raw which allow to work with raw Lua API.
If you more detailed example maybe I can suggest something else.