Alternative FFI designs

[lpil]

The current FFI is based around the idea of functions that live in modules. This works well for Erlang, but does it fit other languages?

JS for example has modules, global functions, and global objects.

External module per package

Rather than functions being able to be imported from any module we could have all external function definitions in a package import from a dedicated external module.

// src/myapp.gleam
pub external fn run() -> Int

% src/external.erl
-module(external).
-export([run/0]).

run() ->
    1.

// src/external.js
export function run() {
  return 1;
}

Here the entrypoint for the native code from Gleam is clearly defined and predictable for us, and is free to import values from anywhere in any way they wish.

We would need to rename the Erlang module at compile time to avoid collisions between packages.

How well would this map on to other languages and platforms we might target in future? How might this work if linking to .so or .dll files in future if we had native compilation? Web assembly? etc