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ecma-runtime-cat

ECMAScript runtime built-ins (console.*, Math.*, JSON.*, parseInt, parseFloat, isNaN, isFinite, Number, String, Boolean) for the boa-cat engine.

ecma-runtime-cat is the runtime layer of a comp-cat-rs reformulation of a JavaScript stack targeting Tauri integration. It registers a set of Rust-implemented NativeFn callables into the engine's initial environment so scripts can call standard globals. The same framework constraints apply: no mut, no Rc/Arc, no interior mutability, no panics, exhaustive matches, static dispatch.

Example

use boa_cat::evaluate_program_with;
use boa_cat::fuel::Fuel;
use ecma_lex_cat::lex;
use ecma_parse_cat::parse_script;
use ecma_runtime_cat::{Error, build_initial};

fn main() -> Result<(), Error> {
    let source = "Math.floor(3.7) + Math.abs(-5)";
    let tokens = lex(source).map_err(boa_cat::Error::from)?;
    let program = parse_script(&tokens).map_err(boa_cat::Error::from)?;
    let (env, heap) = build_initial();
    let (value, _heap) = evaluate_program_with(&program, env, heap, Fuel::new(10_000))?;
    assert_eq!(format!("{value}"), "8");
    Ok(())
}

v0 scope

console.log / console.error / console.warn.
Math.{abs, floor, ceil, round, sqrt, pow, min, max, log, exp, sin, cos, tan, atan, atan2, random} and constants Math.{PI, E, LN2, LN10, SQRT2}.
JSON.stringify (basic; no replacer or space argument).
Globals: parseInt, parseFloat, isNaN, isFinite, Number, String, Boolean, plus undefined, NaN, Infinity.

Deferred to v0.2+

JSON.parse.
Object.{keys, values, entries, assign}.
Array.{isArray, from, of} and Array.prototype.*.
String.prototype.* (requires prototype-chain support in boa-cat).
Date, Promise, Symbol, Error constructor.

Design

Each built-in is a NativeFn (fn(Vec<Value>, Value, Heap, Fuel) -> EvalResult). build_initial() returns a pre-populated (Env, Heap); install(env, heap) folds the runtime onto a caller-supplied env+heap. Downstream callers thread these into boa_cat::evaluate_program_with.

The runtime never panics. Bad inputs surface as Outcome::Throw(Value::String("TypeError: ...")) so script-level try/catch can recover, or as Value::Number(NaN) where ECMA-262 specifies that fallback (parseInt, Number, arithmetic on objects).

License