browserslist 4.29.0: defaults

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 browserslist.defaults in pkg:npm/browserslist@4.29.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/browserslist@4.29.0
Demonstrate these symbols/APIs:
  - browserslist.defaults

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:sha256:42f89ead8da73bcfcecdca70a19473da061f3e8a65dddc9de89c4faacc3be01e","contract":["browserslist.defaults is an array of default query strings including '\u003e 0.5%', 'last 2 versions', 'Firefox ESR', and 'not dead'","browserslist(browserslist.defaults) resolves to an array of supported browser target strings","calling browserslist() without arguments defaults to resolving browserslist.defaults","calling browserslist(null) and browserslist(undefined) fallback to browserslist.defaults","browserslist(browserslist.defaults, options) accepts query options","browserslist throws on invalid query argument shapes"],"goal":"verify browserslist.defaults in pkg:npm/browserslist@4.29.0","kind":"HOW","packages":["pkg:npm/browserslist@4.29.0"],"schemaVersion":1,"symbols":["browserslist.defaults"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/browserslist@4.29.0"],"schemaVersion":1,"subject":"pkg:npm/browserslist@4.29.0","symbols":["browserslist.defaults"],"verifierAdapter":"node-typescript@1"}

import browserslist from 'browserslist';

export const defaults = browserslist.defaults;
export default browserslist;

{
  "name": "sample-browserslist-defaults",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-browserslist-defaults",
      "version": "1.0.0",
      "dependencies": {
        "browserslist": "4.29.0"
      }
    },
    "node_modules/baseline-browser-mapping": {
      "version": "2.11.28",
      "resolved": "https://registry.npmjs.org/baseline-browser-mapping/-/baseline-browser-mapping-2.11.28.tgz",
      "integrity": "sha512-br0LOmjJqr6Rt4AEkadbcNf67Zpo7EPwKsWbjnRrJIa1QYFHQBqM4C7F2WTbV8ahTEcg1Eo+Y0aWjjORInYFyA==",
      "license": "Apache-2.0",
      "bin": {
        "baseline-browser-mapping": "dist/cli.cjs"
      },
      "engines": {
        "node": ">=6.0.0"
      }
    },
    "node_modules/browserslist": {
      "version": "4.29.0",
      "resolved": "https://registry.npmjs.org/browserslist/-/browserslist-4.29.0.tgz",
      "integrity": "sha512-3GSvyjvDI4Dur1Meg2BekJquu5uF+9R9a1+5M1Mde192eZoXbeXjzgOsgqPS2V8D5wrrip0gR5Hf/GhWQ9ZzaA==",
      "funding": [
        {
          "type": "opencollective",
          "url": "https://opencollective.com/browserslist"
        },
        {
          "type": "tidelift",
          "url": "https://tidelift.com/funding/github/npm/browserslist"
        },
        {
          "type": "github",
          "url": "https://github.com/sponsors/ai"
        }
      ],
      "license": "MIT",
      "dependencies": {
        "baseline-browser-mapping": "^2.11.23",
        "caniuse-lite": "^1.0.30001810",
        "electron-to-chromium": "^1.5.427",
        "node-releases": "^2.0.55",
        "update-browserslist-db": "^1.3.3"
      },
      "bin": {
        "browserslist": "cli.js"
      },
      "engines": {
        "node": "^6 || ^7 || ^8 || ^9 || ^10 || ^11 || ^12 || >=13.7"
      }
    },
    "node_modules/caniuse-lite": {
      "version": "1.0.30001815",
      "resolved": "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001815.tgz",
      "integrity": "sha512-uDybUEyfgbyJJ93J1vikTylBX31AkdVYeVPeffMQpf8XN7hSfr0oZOn4VFOIMNvtU5+rHvC5Udg2TgtJKHm23Q==",
      "funding": [
        {
          "type": "opencollective",
          "url": "https://opencollective.com/browserslist"
        },
        {
          "type": "tidelift",
          "url": "https://tidelift.com/funding/github/npm/caniuse-lite"
        },
        {
          "type": "github",
          "url": "https://github.com/sponsors/ai"
        }
      ],
      "license": "CC-BY-4.0"
    },
    "node_modules/electron-to-chromium": {
      "version": "1.5.452",
      "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.5.452.tgz",
      "integrity": "sha512-cVvk1YBSj6571VmV6hdJTqj94Y79xSu8cj6Y9t6ae4Y4431z8/7EJFvu3rVp90xhfuv9BpPKUmaLfTo4+FOGBg==",
      "license": "ISC"
    },
    "node_modules/escalade": {
      "version": "3.2.0",
      "resolved": "https://registry.npmjs.org/escalade/-/escalade-3.2.0.tgz",
      "integrity": "sha512-WUj2qlxaQtO4g6Pq5c29GTcWGDyd8itL8zTlipgECz3JesAiiOKotd8JU6otB3PACgG6xkJUyVhboMS+bje/jA==",
      "license": "MIT",
      "engines": {
        "node": ">=6"
      }
    },
    "node_modules/node-releases": {
      "version": "2.0.58",
      "resolved": "https://registry.npmjs.org/node-releases/-/node-releases-2.0.58.tgz",
      "integrity": "sha512-BdiKAgbfRlvfMq/XzO/AF9NPmaA8a+YpLAyAFTVFBj3gARrAIfWvNq7Q7NE4se3KgFu0KkrvQMxTS0XVnsGzHg==",
      "license": "MIT",
      "engines": {
        "node": ">=18"
      }
    },
    "node_modules/picocolors": {
      "version": "1.1.1",
      "resolved": "https://registry.npmjs.org/picocolors/-/picocolors-1.1.1.tgz",
      "integrity": "sha512-xceH2snhtb5M9liqDsmEw56le376mTZkEX/jEb/RxNFyegNul7eNslCXP9FDj/Lcu0X8KEyMceP2ntpaHrDEVA==",
      "license": "ISC"
    },
    "node_modules/update-browserslist-db": {
      "version": "1.3.4",
      "resolved": "https://registry.npmjs.org/update-browserslist-db/-/update-browserslist-db-1.3.4.tgz",
      "integrity": "sha512-t8wonIOdQyOjtPd2VktlBu6QjTVTks6v8bSi7kd0r2Vll8TK1JYDZtRRdbmCHOAMphkZgrzK+L+vXK4pyZ8t4A==",
      "funding": [
        {
          "type": "opencollective",
          "url": "https://opencollective.com/browserslist"
        },
        {
          "type": "tidelift",
          "url": "https://tidelift.com/funding/github/npm/browserslist"
        },
        {
          "type": "github",
          "url": "https://github.com/sponsors/ai"
        }
      ],
      "license": "MIT",
      "dependencies": {
        "escalade": "^3.2.0",
        "picocolors": "^1.1.1"
      },
      "bin": {
        "update-browserslist-db": "cli.js"
      },
      "peerDependencies": {
        "browserslist": ">= 4.21.0"
      }
    }
  }
}

{
  "name": "sample-browserslist-defaults",
  "version": "1.0.0",
  "type": "module",
  "main": "index.mjs",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "browserslist": "4.29.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify browserslist.defaults in pkg:npm/browserslist@4.29.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/browserslist@4.29.0"
  ],
  "symbols": [
    "browserslist.defaults"
  ]
}

import assert from 'node:assert/strict';
import browserslist from 'browserslist';

// 1. browserslist.defaults is an array of default query strings including '> 0.5%', 'last 2 versions', 'Firefox ESR', and 'not dead'
{
  assert.ok(Array.isArray(browserslist.defaults));
  assert.ok(browserslist.defaults.length > 0);
  assert.deepEqual(browserslist.defaults, [
    '> 0.5%',
    'last 2 versions',
    'Firefox ESR',
    'not dead'
  ]);
}

// 2. browserslist(browserslist.defaults) resolves to an array of supported browser target strings
{
  const explicitTargets = browserslist(browserslist.defaults);
  assert.ok(Array.isArray(explicitTargets));
  assert.ok(explicitTargets.length > 0);
  explicitTargets.forEach((target) => {
    assert.equal(typeof target, 'string');
    assert.ok(target.includes(' '));
  });
}

// 3. calling browserslist() without arguments defaults to resolving browserslist.defaults
{
  const defaultTargets = browserslist();
  const explicitTargets = browserslist(browserslist.defaults);
  assert.deepEqual(defaultTargets, explicitTargets);
}

// 4. calling browserslist(null) and browserslist(undefined) fallback to browserslist.defaults
{
  const explicitTargets = browserslist(browserslist.defaults);
  assert.deepEqual(browserslist(null), explicitTargets);
  assert.deepEqual(browserslist(undefined), explicitTargets);
}

// 5. browserslist(browserslist.defaults, options) accepts query options
{
  const optTargets = browserslist(browserslist.defaults, { env: 'production' });
  assert.ok(Array.isArray(optTargets));
  assert.ok(optTargets.length > 0);
}

// 6. browserslist throws on invalid query argument shapes
{
  assert.throws(() => browserslist(123));
  assert.throws(() => browserslist({ invalid: true }));
}

console.log('All browserslist.defaults contract assertions passed.');