lightningcss 1.33.0: bundle

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 lightningcss.bundle in pkg:npm/lightningcss@1.33.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/lightningcss@1.33.0
Demonstrate these symbols/APIs:
  - lightningcss.bundle

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:c9afc554b532d966de18589ff46ad03a105ed86d1b3dc65780a90067aaf6b285","contract":["bundle inlines nested @import rules into a single CSS output","bundle minifies bundled CSS output when minify option is true","bundle generates source map when sourceMap option is true","bundle generates scoped CSS class names and exports mapping when cssModules option is true","bundle lowers CSS syntax according to specified browser targets","bundle throws an error when an imported file cannot be resolved","bundle throws an error when entry file does not exist"],"goal":"verify lightningcss.bundle in pkg:npm/lightningcss@1.33.0","kind":"HOW","packages":["pkg:npm/lightningcss@1.33.0"],"schemaVersion":1,"symbols":["lightningcss.bundle"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/lightningcss@1.33.0"],"schemaVersion":1,"subject":"pkg:npm/lightningcss@1.33.0","symbols":["lightningcss.bundle"],"verifierAdapter":"node-typescript@1"}

@import "./vars.css";

.card {
  background: var(--main-bg);
  padding: 10px;
}

@import "./reset.css";
@import "./components.css";

body {
  margin: 0;
}

@import "./non-existent-subfile.css";

.test {
  color: red;
}

.btn {
  color: blue;
}

@import "./module-button.css";

.container {
  display: flex;
}

* {
  box-sizing: border-box;
}

.box {
  user-select: none;
  display: flex;
}

:root {
  --main-bg: #fff;
}

{
  "name": "sample-lightningcss-bundle",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-lightningcss-bundle",
      "version": "1.0.0",
      "dependencies": {
        "lightningcss": "1.33.0"
      }
    },
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      "license": "Apache-2.0",
      "engines": {
        "node": ">=8"
      }
    },
    "node_modules/lightningcss": {
      "version": "1.33.0",
      "resolved": "https://registry.npmjs.org/lightningcss/-/lightningcss-1.33.0.tgz",
      "integrity": "sha512-WkUDrojuJs0xkgGf2udWxa3yGBRxPtxUkB79i6aCZLRgc7PM8fZe9TosfPDcvEpQZbuFASnHYmRLBLUbmLOIIA==",
      "license": "MPL-2.0",
      "dependencies": {
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      "engines": {
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      },
      "funding": {
        "type": "opencollective",
        "url": "https://opencollective.com/parcel"
      },
      "optionalDependencies": {
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        "lightningcss-darwin-arm64": "1.33.0",
        "lightningcss-darwin-x64": "1.33.0",
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        "lightningcss-linux-x64-gnu": "1.33.0",
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        "url": "https://opencollective.com/parcel"
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      "version": "1.33.0",
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        "url": "https://opencollective.com/parcel"
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    },
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      "version": "1.33.0",
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      "funding": {
        "type": "opencollective",
        "url": "https://opencollective.com/parcel"
      }
    }
  }
}

{
  "name": "sample-lightningcss-bundle",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "dependencies": {
    "lightningcss": "1.33.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify lightningcss.bundle in pkg:npm/lightningcss@1.33.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/lightningcss@1.33.0"
  ],
  "symbols": [
    "lightningcss.bundle"
  ]
}

import assert from 'node:assert/strict';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import { bundle, browserslistToTargets } from 'lightningcss';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);
const fixturesDir = path.join(__dirname, '..', 'fixtures');

// 1. bundle inlines nested @import rules into a single CSS output
{
  const entryPath = path.join(fixturesDir, 'main.css');
  const result = bundle({
    filename: entryPath,
  });

  const css = result.code.toString();
  assert.ok(css.includes('box-sizing: border-box;'), 'Should include reset styles');
  assert.ok(css.includes('--main-bg: #fff;'), 'Should include variable definitions');
  assert.ok(css.includes('background: var(--main-bg);'), 'Should include component styles');
  assert.ok(css.includes('margin: 0;'), 'Should include body styles');
  assert.ok(!css.includes('@import'), 'All @import statements should be inlined');
}

// 2. bundle minifies bundled CSS output when minify option is true
{
  const entryPath = path.join(fixturesDir, 'main.css');
  const result = bundle({
    filename: entryPath,
    minify: true,
  });

  const css = result.code.toString();
  assert.equal(css.includes('\n'), false, 'Minified CSS should not contain newlines');
  assert.ok(css.includes('*{box-sizing:border-box}'), 'Should minify reset rule');
  assert.ok(css.includes(':root{--main-bg:#fff}'), 'Should minify root variables');
  assert.ok(css.includes('.card{background:var(--main-bg);padding:10px}'), 'Should minify card rule');
  assert.ok(css.includes('body{margin:0}'), 'Should minify body rule');
}

// 3. bundle generates source map when sourceMap option is true
{
  const entryPath = path.join(fixturesDir, 'main.css');
  const result = bundle({
    filename: entryPath,
    sourceMap: true,
  });

  assert.ok(Buffer.isBuffer(result.map), 'result.map should be a Buffer');
  const map = JSON.parse(result.map.toString());
  assert.equal(map.version, 3, 'Source map version should be 3');
  assert.ok(Array.isArray(map.sources), 'Source map should contain sources array');
  assert.ok(map.sources.some((s) => s.endsWith('main.css')), 'Sources should contain main.css');
  assert.ok(map.sources.some((s) => s.endsWith('reset.css')), 'Sources should contain reset.css');
  assert.ok(map.sources.some((s) => s.endsWith('vars.css')), 'Sources should contain vars.css');
  assert.ok(map.sources.some((s) => s.endsWith('components.css')), 'Sources should contain components.css');
}

// 4. bundle generates scoped CSS class names and exports mapping when cssModules option is true
{
  const entryPath = path.join(fixturesDir, 'module-entry.css');
  const result = bundle({
    filename: entryPath,
    cssModules: true,
  });

  assert.ok(result.exports, 'result.exports should be defined');
  assert.ok(result.exports.container, 'result.exports should contain container export');
  assert.ok(typeof result.exports.container.name === 'string', 'container name should be a string');
  assert.ok(result.exports.container.name.includes('container'), 'container name should include local name');
  const css = result.code.toString();
  assert.ok(css.includes(result.exports.container.name), 'Bundled CSS should contain scoped class name');
}

// 5. bundle lowers CSS syntax according to specified browser targets
{
  const entryPath = path.join(fixturesDir, 'target.css');
  const result = bundle({
    filename: entryPath,
    targets: browserslistToTargets(['ie 11']),
    minify: true,
  });

  const css = result.code.toString();
  assert.ok(css.includes('-ms-user-select:none'), 'Should prefix user-select for IE 11');
  assert.ok(css.includes('user-select:none'), 'Should include standard user-select');
}

// 6. bundle throws an error when an imported file cannot be resolved
{
  const entryPath = path.join(fixturesDir, 'missing-import.css');
  assert.throws(
    () => {
      bundle({
        filename: entryPath,
      });
    },
    (err) => {
      return err instanceof Error && (err.name === 'SyntaxError' || err.message.includes('No such file') || err.data === 'ResolverError');
    },
    'Should throw error when imported file does not exist'
  );
}

// 7. bundle throws an error when entry file does not exist
{
  const entryPath = path.join(fixturesDir, 'does-not-exist.css');
  assert.throws(
    () => {
      bundle({
        filename: entryPath,
      });
    },
    (err) => {
      return err instanceof Error && (err.name === 'SyntaxError' || err.message.includes('No such file') || err.data === 'ResolverError');
    },
    'Should throw error when entry file does not exist'
  );
}