lightningcss 1.33.0

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 pkg:npm/lightningcss@1.33.0
Kind: HOW

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

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@import "./theme.css";

.container {
  max-width: 1200px;
}

:root {
  --primary-color: #0070f3;
}

.btn {
  background: var(--primary-color);
  border-radius: 4px;
}

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}

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

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/lightningcss@1.33.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/lightningcss@1.33.0"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

import { bundle, bundleAsync, composeVisitors, transform } from 'lightningcss';

/**
 * Bundles virtual in-memory CSS files using bundleAsync and a custom resolver.
 *
 * @param {string} entryFilename - Root entry filename.
 * @param {Record<string, string>} files - In-memory map of file paths to CSS content.
 * @param {Record<string, string>} [externalMap] - Map of specifiers to external URLs.
 * @returns {Promise<string>} The bundled and minified CSS code.
 */
export async function bundleVirtualStylesheets(entryFilename, files, externalMap = {}) {
  const result = await bundleAsync({
    filename: entryFilename,
    resolver: {
      resolve(specifier) {
        if (externalMap[specifier]) {
          return { external: externalMap[specifier] };
        }
        if (files[specifier]) {
          return specifier;
        }
        throw new Error(`Cannot resolve specifier: ${specifier}`);
      },
      read(file) {
        if (files[file] !== undefined) {
          return files[file];
        }
        throw new Error(`File not found in virtual store: ${file}`);
      }
    },
    minify: true
  });
  return result.code.toString();
}

/**
 * Transforms CSS by composing multiple AST visitors into a single pipeline.
 *
 * @param {string} cssText - Raw CSS source string.
 * @param {Array<import('lightningcss').Visitor<any>>} visitors - Array of AST visitor objects.
 * @returns {string} The transformed CSS code.
 */
export function transformWithComposedVisitors(cssText, visitors) {
  const composed = composeVisitors(visitors);
  const result = transform({
    filename: 'input.css',
    code: Buffer.from(cssText),
    visitor: composed,
    minify: true
  });
  return result.code.toString();
}

/**
 * Bundles CSS files from the filesystem synchronously using bundle.
 *
 * @param {string} entryPath - Path to the root CSS file on disk.
 * @returns {string} The bundled and minified CSS code.
 */
export function bundleFilesystemStylesheet(entryPath) {
  const result = bundle({
    filename: entryPath,
    minify: true
  });
  return result.code.toString();
}

import assert from 'node:assert/strict';
import { fileURLToPath } from 'node:url';
import {
  bundleVirtualStylesheets,
  transformWithComposedVisitors,
  bundleFilesystemStylesheet
} from '../src/index.mjs';

// Contract 1: bundleAsync resolves and inlines relative imports while preserving external import rules with custom in-memory resolver
{
  const virtualFiles = {
    '/virtual/app.css': '@import "external-fonts.css"; @import "/virtual/base.css"; .app { padding: 10px; }',
    '/virtual/base.css': ':root { --main-bg: #f5f5f5; }'
  };
  const externalMap = {
    'external-fonts.css': 'https://fonts.example.com/css2?family=Roboto'
  };

  const output = await bundleVirtualStylesheets('/virtual/app.css', virtualFiles, externalMap);
  assert.ok(
    output.startsWith('@import "https://fonts.example.com/css2?family=Roboto";'),
    'Should preserve external import rule at the beginning'
  );
  assert.ok(
    output.includes(':root{--main-bg:#f5f5f5}'),
    'Should inline base.css variables without @import statement'
  );
  assert.ok(
    output.includes('.app{padding:10px}'),
    'Should include app.css rules'
  );
}

// Contract 2: composeVisitors chains AST transformations for length units and color tokens during minification
{
  const visitorA = {
    Length(len) {
      if (len.unit === 'px' && len.value === 32) {
        return { unit: 'rem', value: 2 };
      }
    }
  };
  const visitorB = {
    Color(color) {
      if (color.type === 'rgb' && color.r === 255 && color.g === 0 && color.b === 0) {
        return { type: 'rgb', r: 0, g: 128, b: 0, alpha: 1 };
      }
    }
  };

  const css = '.hero { font-size: 32px; color: rgb(255, 0, 0); margin: 0; }';
  const transformed = transformWithComposedVisitors(css, [visitorA, visitorB]);
  assert.strictEqual(
    transformed,
    '.hero{color:green;margin:0;font-size:2rem}',
    'Should apply composed visitors for length units and color tokens'
  );
}

// Contract 3: bundle bundles multi-file stylesheets from the filesystem with inlined imports and minification
{
  const fixturePath = fileURLToPath(new URL('../fixtures/main.css', import.meta.url));
  const result = bundleFilesystemStylesheet(fixturePath);
  assert.strictEqual(
    result,
    ':root{--primary-color:#0070f3}.btn{background:var(--primary-color);border-radius:4px}.container{max-width:1200px}',
    'Should bundle and minify imported filesystem stylesheets'
  );
}

console.log('All lightningcss 1.33.0 contracts passed successfully.');