Ez

A high-performance JavaScript/TypeScript parser and linter written in Zig, with a zero-copy ESLint plugin runner that lets you run any ESLint plugin without reimplementing its rules.

Parser Conformance

Suite	Must-parse	Must-reject	Notes
tc39/test262-parser-tests	3,966/3,966 (100%)	1,387/1,391 (99.7%)	6 known-stale skipped
TypeScript	3,466/3,466 (100%)	583/1,009 (57.8%)	1,432 skipped (decorators etc.)
Babel (JS)	3,911/4,122 (94.9%)	1,583/1,587 (99.7%)	2,871 skipped (JSX/TS/proposals)

Must-reject measures whether the parser correctly reports a parse error on invalid code. TypeScript's low must-reject score (57.8%) reflects missing TS-specific error detection — ez parses the code without crashing but doesn't yet diagnose all TypeScript semantic/syntax violations.

Features

• Zig-native parser — SIMD-accelerated lexer, arena allocation, MultiArrayList AST (struct-of-arrays layout)
• Semantic analysis — scope tree, symbol table, reference tracking
• Zero-copy JS bridge — AST is shared as a raw ArrayBuffer; Node.js reads it without copying or marshalling
• ESLint plugin runner — load any ESLint plugin via require() and run its rules against the ez AST
• ESTree-compatible node views — named field getters (node.test, node.consequent, node.body, etc.), node.parent, node.range, node.loc
• AST selectors — esquery-style selectors in visitor keys ("IfStatement > BlockStatement", "CallExpression[callee.name='require']")
• Autofix — --fix applies rule-provided fixes in-place
• Full SourceCode API — getText(), getTokenBefore/After(), getScope(), getAncestors()

ESLint Plugin Compatibility

Tested against current versions:

Plugin	Rules passing
eslint (core)	292/292
eslint-plugin-n	43/43
eslint-plugin-es-x	208/208
eslint-plugin-import	45/46

Quick Start

Build the native module

zig build          # builds zig-out/lib/libez.{dylib,so,dll}

Install JS dependencies

cd js && npm install

Run lint rules

# Run all eslint core rules against a file or directory
node js/lint.js --eslint-plugin eslint src/

# Run a specific rule
node js/lint.js --eslint-plugin eslint --rule eqeqeq src/index.js

# Run a third-party plugin
node js/lint.js --eslint-plugin eslint-plugin-unicorn src/

# TypeScript-eslint plugin
node js/lint.js --eslint-plugin @typescript-eslint/eslint-plugin src/

# Multiple plugins
node js/lint.js -p eslint -p eslint-plugin-n src/

# Apply autofixes
node js/lint.js --eslint-plugin eslint --fix src/

# JSON output
node js/lint.js --eslint-plugin eslint --format=json src/ | jq .

# With a config file for rule options
node js/lint.js --eslint-plugin eslint --config .eslintrc.json src/

CLI options

--eslint-plugin, -p <pkg>   Load ESLint plugin (repeatable)
--rule, -r <name>           Only run rules matching this name (repeatable)
--config, -c <file>         ESLint config file (.eslintrc.json) for rule options
--format=json               Output JSON array instead of text
--fix                       Apply autofixes to files (writes in place)
--help, -h                  Show help

How It Works

Ez serializes its AST into a flat ArrayBuffer that is shared directly with Node.js — no JSON, no copying. The JS side reads node tags, tokens, and extra data via typed array views on the same memory. ESLint plugin rules call context.report() as normal; ez collects the reports and formats them.

See DESIGN.md for the full architecture: MultiArrayList AST layout, SIMD lexer, arena allocation, and the JS bridge protocol.

Requirements

• Zig 0.16.0-dev or later
• Node.js 18+ (for the JS plugin runner)

License

MIT