Support globals in Quickjs.eval_code

[ollym]

Summary

• add a globals: option to Quickjs.eval_code and Quickjs::VM.new
• expose supplied Ruby values as JavaScript globals through QuickJS's native C API
• reuse the existing Ruby-to-JavaScript converter for primitives, arrays, and hashes
• document the API and add focused coverage for conversion and invalid input

Why

Callers currently need to interpolate values into JavaScript source. Native variable injection provides a concise API without generating a JavaScript wrapper or changing QuickJS core:

Quickjs.eval_code("a + b", globals: { a: 1, b: 2 }) # => 3

The values are installed on the new VM's global object during native initialization, before the code is evaluated.

Validation

• bundle exec rake
• 500 tests, 775 assertions, 0 failures, 1 existing skip
• RBS validation passes

[hmsk]

Thanks for the PR, and for covering docs, RBS and tests.

It's a real gap. My own README examples interpolate values into JS source, so this is on me to solve. I'd like to get the shape right first though, because "globals" turns out to be ambiguous here: let / const declarations persist across eval_code calls, but never appear on globalThis.

vm.eval_code('globalThis.a = 1;')   # what this PR does
vm.eval_code('let a = 2; a')        #=> 2
vm.eval_code('globalThis.a')        #=> 1

Two live values under one name. Related: the injected value is a one-time copy, though globals: { user: user } reads like it hands over the object.

Works today

define_function covers most of this, and a call site makes the crossing into Ruby explicit:

vm.define_function('a') { 1 }
vm.define_function('b') { 2 }
vm.eval_code('a() + b()')  #=> 3

vm.define_function('user') { user }   # returns go through the same converter
vm.eval_code('user().name')           #=> "Itadori", and stays live if you mutate `user`

For JS you don't control that expects the global to exist already, pin it once at setup and leave the JS untouched:

vm.eval_code('globalThis.user = user();')

The gap that leaves is one-shot Quickjs.eval_code, since there's no VM handle to define on. That's the case I want to design around.

I'm still doodling ideal APIs. I'll open a PR and link it here, feedback welcome when I do.