react-dom 19.2.8: prerenderToNodeStream

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 prerenderToNodeStream in pkg:npm/react-dom@19.2.8
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/react-dom@19.2.8
Demonstrate these symbols/APIs:
  - prerenderToNodeStream
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:sha256:2ed4d0025947230a9df27c2a8c396c4396e4887577d5a4d977531427f6da5086","constraints":{"executionContext":"node"},"contract":["prerenderToNodeStream(element) returns a Promise resolving to { prelude, postponed }","prelude is a Readable stream emitting rendered HTML chunks for the React element tree","postponed is null when prerendering a fully static React component tree","identifierPrefix option in prerenderToNodeStream options configures prefixes for useId hook generated IDs"],"goal":"verify prerenderToNodeStream in pkg:npm/react-dom@19.2.8","kind":"HOW","packages":["pkg:npm/react-dom@19.2.8"],"schemaVersion":1,"symbols":["prerenderToNodeStream"]},"contractCommand":["node","test/contract.js"],"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/react-dom@19.2.8"],"schemaVersion":1,"subject":"pkg:npm/react-dom@19.2.8","symbols":["prerenderToNodeStream"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-2971405431",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-2971405431",
      "version": "1.0.0",
      "license": "ISC",
      "dependencies": {
        "react": "19.2.8",
        "react-dom": "19.2.8"
      }
    },
    "node_modules/react": {
      "version": "19.2.8",
      "resolved": "https://registry.npmjs.org/react/-/react-19.2.8.tgz",
      "integrity": "sha512-PWaYA1L/q9u2u7xYQi+Y3L3Yfnie7XyLeaJICV1MGD6LprsBxcAqGjYyr0eY3p+QdsA+x/Irkt4Qif8D63+Sbw==",
      "license": "MIT",
      "engines": {
        "node": ">=0.10.0"
      }
    },
    "node_modules/react-dom": {
      "version": "19.2.8",
      "resolved": "https://registry.npmjs.org/react-dom/-/react-dom-19.2.8.tgz",
      "integrity": "sha512-rVprimfGBG3DR+Tq0IQG2DT5PxKth1WIGDmj5yPmlzr4YBe7uyE+Du4oVqTDXZSHGGGXRtTJEGSSePyQCMBglQ==",
      "license": "MIT",
      "dependencies": {
        "scheduler": "^0.27.0"
      },
      "peerDependencies": {
        "react": "^19.2.8"
      }
    },
    "node_modules/scheduler": {
      "version": "0.27.0",
      "resolved": "https://registry.npmjs.org/scheduler/-/scheduler-0.27.0.tgz",
      "integrity": "sha512-eNv+WrVbKu1f3vbYJT/xtiF5syA5HPIMtf9IgY/nKg0sWqzAUEvqY/xm7OcZc/qafLx/iO9FgOmeSAp4v5ti/Q==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-2971405431",
  "version": "1.0.0",
  "description": "verify prerenderToNodeStream in pkg:npm/react-dom@19.2.8",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "keywords": [],
  "author": "",
  "license": "MIT-0",
  "dependencies": {
    "react": "19.2.8",
    "react-dom": "19.2.8"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify prerenderToNodeStream in pkg:npm/react-dom@19.2.8",
  "kind": "HOW",
  "packages": [
    "pkg:npm/react-dom@19.2.8"
  ],
  "symbols": [
    "prerenderToNodeStream"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const React = require('react');
const { prerenderToNodeStream } = require('react-dom/static.node');

/**
 * Prerenders a React element tree to an HTML string using Node stream.
 * @param {React.ReactElement} element
 * @param {object} [options]
 * @returns {Promise<{ html: string, postponed: object|null }>}
 */
async function renderToHtml(element, options = {}) {
  const { prelude, postponed } = await prerenderToNodeStream(element, options);

  let html = '';
  for await (const chunk of prelude) {
    html += chunk.toString();
  }

  return { html, postponed };
}

module.exports = {
  renderToHtml,
  prerenderToNodeStream
};

const assert = require('node:assert/strict');
const React = require('react');
const { prerenderToNodeStream } = require('react-dom/static.node');
const { renderToHtml } = require('../src/index.js');

async function testBasicPrerender() {
  const element = React.createElement('div', { className: 'container' },
    React.createElement('h1', null, 'Hello World'),
    React.createElement('p', null, 'Static Prerender')
  );

  const { prelude, postponed } = await prerenderToNodeStream(element);

  assert.ok(prelude, 'prelude stream should be defined');
  assert.ok(typeof prelude.pipe === 'function', 'prelude should be a Readable stream');
  assert.equal(postponed, null, 'postponed should be null for static tree');

  let html = '';
  for await (const chunk of prelude) {
    html += chunk.toString();
  }

  assert.equal(html, '<div class="container"><h1>Hello World</h1><p>Static Prerender</p></div>');
}

async function testHelperRenderToHtml() {
  const App = ({ name }) => React.createElement('article', { 'data-testid': 'article' }, `Welcome, ${name}!`);
  const element = React.createElement(App, { name: 'CodeSampleX' });

  const result = await renderToHtml(element);
  assert.equal(result.html, '<article data-testid="article">Welcome, CodeSampleX!</article>');
  assert.equal(result.postponed, null);
}

async function testPrerenderWithOptions() {
  const ComponentWithId = () => {
    const id = React.useId();
    return React.createElement('div', { id }, 'Item with ID');
  };

  const { prelude } = await prerenderToNodeStream(React.createElement(ComponentWithId), {
    identifierPrefix: 'csx-'
  });

  let html = '';
  for await (const chunk of prelude) {
    html += chunk.toString();
  }

  assert.match(html, /id=".*csx-.*"/, 'identifierPrefix option should prefix generated IDs');
}

async function runAll() {
  await testBasicPrerender();
  await testHelperRenderToHtml();
  await testPrerenderWithOptions();
  console.log('All prerenderToNodeStream contract tests passed.');
}

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