Ruby::Box support—is it possible in Ruby WASM?

[brandonzylstra]

Is it possible to enable Ruby::Box in Ruby WASM?

[ledsun]

Yes, Ruby::Box can run on ruby.wasm.

Importantly, to enable Ruby::Box, you must specify RUBY_BOX=1 as an environment variable when starting the Ruby VM. Setting ENV[“RUBY_BOX”] = “1” from within Ruby code is too late.

For example, this works on Node.js:

import fs from "fs/promises";
import { DefaultRubyVM } from "@ruby/wasm-wasi/dist/node";

const binary = await fs.readFile(
  "./node_modules/@ruby/head-wasm-wasi/dist/ruby.wasm",
);
const module = await WebAssembly.compile(binary);

const { vm } = await DefaultRubyVM(module, {
  env: {
    RUBY_BOX: "1",
  },
});

const result = vm.eval(`
  box = Ruby::Box.new
  box.eval <<~RUBY
    X = 123
  RUBY

  puts "Ruby::Box.enabled?: #{Ruby::Box.enabled?}"
  puts "box::X: #{box::X}"
`);

Example output:

$ node ruby-box.node.js
(node:8080) ExperimentalWarning: WASI is an experimental feature and might change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
ruby.wasm: warning: Ruby::Box is experimental, and the behavior may change in the future!
See https://docs.ruby-lang.org/en/master/Ruby/Box.html for known issues, etc.
Ruby::Box.enabled?: true
box::X: 123

The same applies in browsers if you instantiate the VM manually, e.g. by passing env to DefaultRubyVM:

const { vm } = await DefaultRubyVM(module, {
  env: {
    RUBY_BOX: "1",
  },
});

Note

Currently, browser.script.iife.js does not provide a way to pass environment variables from HTML.

[brandonzylstra]

Are there any plans to update browser.script.iffe.js to make it easy to pass in custom options?