postcss 8.5.26: parse

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 postcss.parse in pkg:npm/postcss@8.5.26
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/postcss@8.5.26
Demonstrate these symbols/APIs:
  - postcss.parse

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:ae61485afade347c3dffe2352fbb39afdfb1b5fea06cd6034cf0c57701629fa3","contract":["postcss.parse is exported as a function from postcss","postcss.parse returns a Root AST node with type 'root' for valid CSS string","postcss.parse populates child nodes with rule, declaration, and at-rule AST structures","postcss.parse accepts options object including from path and propagates to source.input","postcss.parse handles comments and whitespace without losing structural nodes","postcss.parse throws CssSyntaxError when parsing malformed or unclosed CSS blocks","postcss.parse parsed Root node serializes back to CSS string matching input via toString"],"goal":"verify postcss.parse in pkg:npm/postcss@8.5.26","kind":"HOW","packages":["pkg:npm/postcss@8.5.26"],"schemaVersion":1,"symbols":["postcss.parse"]},"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/postcss@8.5.26"],"schemaVersion":1,"subject":"pkg:npm/postcss@8.5.26","symbols":["postcss.parse"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-postcss-parse",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-postcss-parse",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "postcss": "8.5.26"
      }
    },
    "node_modules/nanoid": {
      "version": "3.3.18",
      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.18.tgz",
      "integrity": "sha512-DTg4MJbGMWkfi6VZFdNt2/caMbQy4Ou+Op/hJQvGEWcnVfoA1QA+xzRKAzw9jD6+GVOOeYr/mIcuDSdug6F6+w==",
      "funding": [
        {
          "type": "github",
          "url": "https://github.com/sponsors/ai"
        }
      ],
      "license": "MIT",
      "bin": {
        "nanoid": "bin/nanoid.cjs"
      },
      "engines": {
        "node": "^10 || ^12 || ^13.7 || ^14 || >=15.0.1"
      }
    },
    "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/postcss": {
      "version": "8.5.26",
      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.26.tgz",
      "integrity": "sha512-u82N74LFzG8ca+dD8puPnplTXoGH4fTPpVGuIbt36G3qvNlkvfD0lEAZSxaly3KX8TS/L1A1gsCEmvKmBcVbkQ==",
      "funding": [
        {
          "type": "opencollective",
          "url": "https://opencollective.com/postcss/"
        },
        {
          "type": "tidelift",
          "url": "https://tidelift.com/funding/github/npm/postcss"
        },
        {
          "type": "github",
          "url": "https://github.com/sponsors/ai"
        }
      ],
      "license": "MIT",
      "dependencies": {
        "nanoid": "^3.3.17",
        "picocolors": "^1.1.1",
        "source-map-js": "^1.2.1"
      },
      "engines": {
        "node": "^10 || ^12 || >=14"
      }
    },
    "node_modules/source-map-js": {
      "version": "1.2.1",
      "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.1.tgz",
      "integrity": "sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==",
      "license": "BSD-3-Clause",
      "engines": {
        "node": ">=0.10.0"
      }
    }
  }
}

{
  "name": "sample-postcss-parse",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room code sample for postcss.parse in postcss@8.5.26",
  "main": "src/index.js",
  "license": "MIT-0",
  "dependencies": {
    "postcss": "8.5.26"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify postcss.parse in pkg:npm/postcss@8.5.26",
  "kind": "HOW",
  "packages": [
    "pkg:npm/postcss@8.5.26"
  ],
  "symbols": [
    "postcss.parse"
  ]
}

const postcss = require('postcss');

/**
 * Parses CSS text into a PostCSS AST Root node.
 *
 * @param {string} css - The CSS string to parse.
 * @param {object} [opts] - Optional parsing options (e.g. { from: string }).
 * @returns {object} PostCSS Root AST node.
 */
function parseCss(css, opts) {
  return postcss.parse(css, opts);
}

/**
 * Checks whether a given string contains valid CSS syntax without throwing.
 *
 * @param {string} css - The CSS string to check.
 * @returns {boolean} True if syntax is valid CSS, false otherwise.
 */
function isValidCss(css) {
  try {
    postcss.parse(css);
    return true;
  } catch (err) {
    if (err.name === 'CssSyntaxError') {
      return false;
    }
    throw err;
  }
}

/**
 * Extracts all rule selectors from CSS string.
 *
 * @param {string} css - The CSS string to inspect.
 * @returns {string[]} Array of selector strings.
 */
function extractSelectors(css) {
  const root = postcss.parse(css);
  const selectors = [];
  root.walkRules((rule) => {
    selectors.push(rule.selector);
  });
  return selectors;
}

module.exports = {
  postcss,
  parseCss,
  isValidCss,
  extractSelectors
};

import assert from 'node:assert/strict';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const {
  postcss,
  parseCss,
  isValidCss,
  extractSelectors
} = require('../src/index.js');

async function runTests() {
  // 1. postcss.parse is exported as a function from postcss
  assert.equal(typeof postcss.parse, 'function', 'postcss.parse must be a function');
  assert.equal(typeof parseCss, 'function', 'parseCss helper must be a function');
  assert.equal(typeof isValidCss, 'function', 'isValidCss helper must be a function');
  assert.equal(typeof extractSelectors, 'function', 'extractSelectors helper must be a function');

  // 2. postcss.parse returns a Root AST node with type 'root' for valid CSS string
  const emptyRoot = parseCss('');
  assert.equal(emptyRoot.type, 'root', 'Empty string parses to a root AST node');
  assert.equal(Array.isArray(emptyRoot.nodes), true, 'root.nodes must be an array');
  assert.equal(emptyRoot.nodes.length, 0, 'Empty CSS produces zero nodes');

  const css = 'a { color: red; }';
  const root = parseCss(css);
  assert.equal(root.type, 'root', 'Root node type must be root');
  assert.equal(root.nodes.length, 1, 'Single rule produces one top-level node');

  // 3. postcss.parse populates child nodes with rule, declaration, and at-rule AST structures
  const complexCss = `
    @charset "UTF-8";
    @media (min-width: 600px) {
      .card {
        padding: 16px;
        margin: 0 auto;
      }
    }
    h1, h2 {
      font-size: 2rem;
    }
  `;
  const complexRoot = parseCss(complexCss);
  assert.equal(complexRoot.nodes.length, 3, 'Expected 3 top-level nodes in complex CSS');

  const [atCharset, atMedia, ruleH] = complexRoot.nodes;
  assert.equal(atCharset.type, 'atrule');
  assert.equal(atCharset.name, 'charset');
  assert.equal(atCharset.params, '"UTF-8"');

  assert.equal(atMedia.type, 'atrule');
  assert.equal(atMedia.name, 'media');
  assert.equal(atMedia.params, '(min-width: 600px)');
  assert.equal(atMedia.nodes.length, 1);
  assert.equal(atMedia.first.type, 'rule');
  assert.equal(atMedia.first.selector, '.card');
  assert.equal(atMedia.first.nodes.length, 2);
  assert.equal(atMedia.first.nodes[0].type, 'decl');
  assert.equal(atMedia.first.nodes[0].prop, 'padding');
  assert.equal(atMedia.first.nodes[0].value, '16px');
  assert.equal(atMedia.first.nodes[1].type, 'decl');
  assert.equal(atMedia.first.nodes[1].prop, 'margin');
  assert.equal(atMedia.first.nodes[1].value, '0 auto');

  assert.equal(ruleH.type, 'rule');
  assert.equal(ruleH.selector, 'h1, h2');
  assert.equal(ruleH.first.type, 'decl');
  assert.equal(ruleH.first.prop, 'font-size');
  assert.equal(ruleH.first.value, '2rem');

  const selectors = extractSelectors(complexCss);
  assert.deepEqual(selectors, ['.card', 'h1, h2']);

  // 4. postcss.parse accepts options object including from path and propagates to source.input
  const rootWithOptions = parseCss('body { margin: 0; }', { from: '/path/to/style.css' });
  assert.ok(rootWithOptions.source, 'Root node has source information');
  assert.ok(rootWithOptions.source.input, 'Source has input descriptor');
  assert.equal(rootWithOptions.source.input.from, '/path/to/style.css', 'from option is preserved on input');

  // 5. postcss.parse handles comments and whitespace without losing structural nodes
  const commentedCss = '/* header styles */ nav { display: flex; /* align */ }';
  const commentedRoot = parseCss(commentedCss);
  assert.equal(commentedRoot.nodes.length, 2, 'Comment and rule are top-level nodes');
  assert.equal(commentedRoot.nodes[0].type, 'comment');
  assert.equal(commentedRoot.nodes[0].text, 'header styles');
  assert.equal(commentedRoot.nodes[1].type, 'rule');
  assert.equal(commentedRoot.nodes[1].nodes.length, 2);
  assert.equal(commentedRoot.nodes[1].nodes[0].type, 'decl');
  assert.equal(commentedRoot.nodes[1].nodes[1].type, 'comment');
  assert.equal(commentedRoot.nodes[1].nodes[1].text, 'align');

  // 6. postcss.parse throws CssSyntaxError when parsing malformed or unclosed CSS blocks
  const invalidCss = 'a { color: red';
  assert.equal(isValidCss('a { color: red; }'), true);
  assert.equal(isValidCss(invalidCss), false);

  assert.throws(
    () => parseCss(invalidCss),
    (err) => {
      assert.equal(err.name, 'CssSyntaxError', 'Error name must be CssSyntaxError');
      assert.equal(typeof err.line, 'number', 'CssSyntaxError must have line number');
      assert.equal(typeof err.column, 'number', 'CssSyntaxError must have column number');
      assert.equal(typeof err.reason, 'string', 'CssSyntaxError must have reason string');
      return true;
    }
  );

  // 7. postcss.parse parsed Root node serializes back to CSS string matching input via toString
  const inputSnippet = 'button.primary { background-color: #007bff; border: none; }';
  const parsedRoot = parseCss(inputSnippet);
  assert.equal(parsedRoot.toString(), inputSnippet, 'toString() output must match original input text');

  console.log('All contract assertions for postcss.parse passed successfully.');
}

runTests().catch((err) => {
  console.error('Contract test failed:', err);
  process.exit(1);
  });