@eslint-community/regexpp 4.12.2: RegExpParser

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify RegExpParser in pkg:npm/%40eslint-community/regexpp@4.12.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40eslint-community/regexpp@4.12.2
Demonstrate these symbols/APIs:
  - RegExpParser
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:51d5295529f4069531cfd24a2bfb23c255c52868951dcc16497cb2dacb8ddc76","constraints":{"executionContext":"node"},"contract":["RegExpParser constructor accepts options and instantiates a parser","parseLiteral parses complete regular expression literals into AST with pattern and flags","parseFlags extracts valid RegExp flag properties into a Flags AST node","parsePattern parses pattern string into a Pattern AST node with unicode flags option","parseLiteral and parsePattern throw RegExpSyntaxError on invalid regular expression syntax","parseFlags throws RegExpSyntaxError on duplicate or invalid flag characters"],"goal":"verify RegExpParser in pkg:npm/%40eslint-community/regexpp@4.12.2","kind":"HOW","packages":["pkg:npm/%40eslint-community/regexpp@4.12.2"],"schemaVersion":1,"symbols":["RegExpParser"]},"contractCommand":["node","test/contract.cjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40eslint-community/regexpp@4.12.2"],"schemaVersion":1,"subject":"pkg:npm/%40eslint-community/regexpp@4.12.2","symbols":["RegExpParser"],"verifierAdapter":"node-typescript@1"}

const { RegExpParser, RegExpSyntaxError } = require('@eslint-community/regexpp');

/**
 * Creates a RegExpParser instance with the provided options.
 *
 * @param {import('@eslint-community/regexpp').RegExpParser.Options} [options]
 * @returns {RegExpParser}
 */
function createParser(options) {
  return new RegExpParser(options);
}

/**
 * Parses a complete RegExp literal string into an AST.
 *
 * @param {string} source
 * @param {import('@eslint-community/regexpp').RegExpParser.Options} [options]
 * @returns {import('@eslint-community/regexpp/ast').RegExpLiteral}
 */
function parseLiteral(source, options) {
  const parser = new RegExpParser(options);
  return parser.parseLiteral(source);
}

/**
 * Parses RegExp flags string into a Flags AST node.
 *
 * @param {string} flags
 * @param {import('@eslint-community/regexpp').RegExpParser.Options} [options]
 * @returns {import('@eslint-community/regexpp/ast').Flags}
 */
function parseFlags(flags, options) {
  const parser = new RegExpParser(options);
  return parser.parseFlags(flags);
}

/**
 * Parses a RegExp pattern string into a Pattern AST node.
 *
 * @param {string} pattern
 * @param {object} [flags]
 * @param {import('@eslint-community/regexpp').RegExpParser.Options} [options]
 * @returns {import('@eslint-community/regexpp/ast').Pattern}
 */
function parsePattern(pattern, flags, options) {
  const parser = new RegExpParser(options);
  return parser.parsePattern(pattern, 0, pattern.length, flags);
}

module.exports = {
  RegExpParser,
  RegExpSyntaxError,
  createParser,
  parseLiteral,
  parseFlags,
  parsePattern,
};

{
  "name": "sample-regexpp-regexp-parser",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-regexpp-regexp-parser",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "@eslint-community/regexpp": "4.12.2"
      }
    },
    "node_modules/@eslint-community/regexpp": {
      "version": "4.12.2",
      "resolved": "https://registry.npmjs.org/@eslint-community/regexpp/-/regexpp-4.12.2.tgz",
      "integrity": "sha512-EriSTlt5OC9/7SXkRSCAhfSxxoSUgBm33OH+IkwbdpgoqsSsUg7y3uh+IICI/Qg4BBWr3U2i39RpmycbxMq4ew==",
      "license": "MIT",
      "engines": {
        "node": "^12.0.0 || ^14.0.0 || >=16.0.0"
      }
    }
  }
}

{
  "name": "sample-regexpp-regexp-parser",
  "version": "1.0.0",
  "type": "commonjs",
  "private": true,
  "dependencies": {
    "@eslint-community/regexpp": "4.12.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify RegExpParser in pkg:npm/%40eslint-community/regexpp@4.12.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40eslint-community/regexpp@4.12.2"
  ],
  "symbols": [
    "RegExpParser"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const assert = require('node:assert/strict');
const {
  RegExpParser,
  RegExpSyntaxError,
  createParser,
  parseLiteral,
  parseFlags,
  parsePattern,
} = require('../index.js');

// Contract 1: RegExpParser constructor accepts options and instantiates a parser
{
  const parser = createParser({ ecmaVersion: 2025, strict: true });
  assert.ok(parser instanceof RegExpParser);
  assert.strictEqual(typeof parser.parseLiteral, 'function');
  assert.strictEqual(typeof parser.parseFlags, 'function');
  assert.strictEqual(typeof parser.parsePattern, 'function');
}

// Contract 2: parseLiteral parses complete regular expression literals into AST with pattern and flags
{
  const ast = parseLiteral('/(?<year>\\d{4})-(?<month>\\d{2})/u');
  assert.strictEqual(ast.type, 'RegExpLiteral');
  assert.strictEqual(ast.parent, null);
  assert.strictEqual(ast.flags.type, 'Flags');
  assert.strictEqual(ast.flags.unicode, true);
  assert.strictEqual(ast.flags.global, false);
  assert.strictEqual(ast.pattern.type, 'Pattern');
  assert.strictEqual(ast.pattern.alternatives.length, 1);
  const alt = ast.pattern.alternatives[0];
  assert.strictEqual(alt.type, 'Alternative');
  assert.strictEqual(alt.elements.length, 3);
  assert.strictEqual(alt.elements[0].type, 'CapturingGroup');
  assert.strictEqual(alt.elements[0].name, 'year');
}

// Contract 3: parseFlags extracts valid RegExp flag properties into a Flags AST node
{
  const flags = parseFlags('gimsv');
  assert.strictEqual(flags.type, 'Flags');
  assert.strictEqual(flags.global, true);
  assert.strictEqual(flags.ignoreCase, true);
  assert.strictEqual(flags.multiline, true);
  assert.strictEqual(flags.dotAll, true);
  assert.strictEqual(flags.unicodeSets, true);
  assert.strictEqual(flags.unicode, false);
  assert.strictEqual(flags.sticky, false);
}

// Contract 4: parsePattern parses pattern string into a Pattern AST node with unicode flags option
{
  const pattern = parsePattern('^[a-z]+$', { unicode: true });
  assert.strictEqual(pattern.type, 'Pattern');
  assert.strictEqual(pattern.alternatives.length, 1);
  const elements = pattern.alternatives[0].elements;
  assert.strictEqual(elements[0].type, 'Assertion');
  assert.strictEqual(elements[0].kind, 'start');
  assert.strictEqual(elements[1].type, 'Quantifier');
  assert.strictEqual(elements[1].min, 1);
  assert.strictEqual(elements[1].max, Infinity);
  assert.strictEqual(elements[2].type, 'Assertion');
  assert.strictEqual(elements[2].kind, 'end');
}

// Contract 5: parseLiteral and parsePattern throw RegExpSyntaxError on invalid regular expression syntax
{
  assert.throws(
    () => {
      parseLiteral('/[a-/');
    },
    (err) => {
      return err instanceof RegExpSyntaxError;
    }
  );

  assert.throws(
    () => {
      parsePattern('(?<1invalid>\\w+)');
    },
    (err) => {
      return err instanceof RegExpSyntaxError;
    }
  );
}

// Contract 6: parseFlags throws RegExpSyntaxError on duplicate or invalid flag characters
{
  assert.throws(
    () => {
      parseFlags('gg');
    },
    (err) => {
      return err instanceof RegExpSyntaxError;
    }
  );

  assert.throws(
    () => {
      parseFlags('z');
    },
    (err) => {
      return err instanceof RegExpSyntaxError;
    }
  );
}

console.log('All contracts passed.');