spite

A JavaScript parser and interpreter written in safe Rust.

spite targets ECMAScript 2026. It implements an initial subset and is not a conforming engine yet. Node.js compatibility, browser APIs, and syntax extensions are outside its scope.

Production crates use std and workspace crates, plus jiff/jiff-tzdb for time zones. The design also permits regex or regress for matching when needed. Workspace lints forbid unsafe code. insta is used only for tests.

Run

Rust 1.85 or later is required.

cargo run -p spite -- --eval 'let x = 6; x * 7'
cargo run -p spite -- example.js
printf '1 + 2' | cargo run -p spite -- -

The CLI prints the Script's completion value. Strings use a quoted representation that preserves lone surrogates. Source input must be UTF-8. The host installs no console, process, filesystem, or other non-standard JavaScript globals.

Host resource quotas are disabled by default. Supply --max-steps N before the input arguments to opt into a per-Script work limit. Work units count interpreter and builtin operations, rather than JavaScript statements or elapsed time.

Test

Run the workspace tests, documentation tests, and complete reviewed Test262 corpus:

python3 tools/run-cargo-workspace-tests.py --toolchain stable
cargo +stable test --workspace --doc --locked
cargo +stable test -p spite-test262 --profile conformance --test corpus --locked pinned_corpus_runs_all_reviewed_variants -- --exact

The workspace runner executes Cargo's test invocations with their original arguments and environment, leaving the full corpus to the separate command. Core test builds optimize the exhaustive Unicode checks. Debug assertions and overflow checks remain enabled; interpreter and integration test builds retain their normal unoptimized profile. Test builds retain line and function debug information while omitting full variable and type details to reduce linking costs. Link-time optimization is disabled for test builds.

The complete Test262 gate explicitly uses two corpus workers. Every reviewed variant runs, and reports retain manifest order. Each evaluated variant uses a fresh realm, ordinary native stacks, and runtime defaults with JavaScript quotas disabled. The library's run_corpus API and the CLI use serial execution.

Runtime integration cases live under crates/spite-runtime/tests/cases and share one harness. For example, run a subset with cargo test -p spite-runtime --test integration regexp_unicode_devanagari_script. Add each new case file to the harness module list; CI checks for omitted or duplicate files. Keep fixture helpers under cases/fixtures.

Embed

use spite::{Realm, Value};

let mut realm = Realm::default();
assert_eq!(realm.eval("let x = 6; x * 7").unwrap(), Value::Number(42.0));

Embedders can opt into an execution work limit with Realm::new(Limits { max_steps: Some(100_000), ..Limits::default() }). Every Limits field is optional and defaults to None. For example, max_heap_entries: Some(10_000) opts into a shared object/environment slot quota. Platform capacity checks and the interpreter's native-stack guards remain active.

The workspace contains spite-core, spite-parser, spite-runtime, and the spite facade and CLI. All members live under crates/.

See the design, roadmap, and current coverage. GitHub Actions checks formatting, Clippy, unit and integration tests, documentation tests, dependency policy, and pinned Test262 fixture integrity on each push and pull request. Tests run on Linux and Windows with stable Rust and the minimum supported Rust version.