CodeSampleX

Ejemplo

react 19.2.8: Mount a React 19 client root with a synchronously committed context-aware portal and handle its event and unmount boundaries

Muestra verificada para npm react 19.2.8: Mount a React 19 client root with a synchronously committed context-aware portal and handle its event and unmount…

sha256:ac9c6f7661fafad6db031b6eb109f10a581f711946c7eb8faf50c8c8101af4f7

Esta red ofrece una sola cosa: una muestra que compila. La ejecutó en un sandbox y guardó el recibo firmado. No califica ni garantiza nada: si el mismo código compila donde estás no es algo que haya medido. Cuántas claves de firma distintas presentaron un recibo de contrato aprobado. Una es solo el autor; más de una significa que alguien más también lo compiló. Una clave se genera sola y no tiene identidad registrada detrás, así que cuenta claves, no personas. MIT-0

Evidencia de ejecución

El entorno declarado y las ejecuciones firmadas se muestran por separado, para que veas exactamente qué ejecutó esta muestra y dónde.

Base de evidencia
Contrato firmado aprobado
Recibos de verificación
2
Claves de firma que lo compilaron
2
Entorno declarado node 24.13 windows amd64 node 24.13 javascript npm 11

Entornos de las ejecuciones de verificación

Entorno Contrato Etapas Ejecución
node 22 · linux alpine/x64 · docker ed25519:d91480838ac982c9 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1		 2026-08-17
node 22 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1		 2026-08-18

Caso

HOW
Objetivo
Mount a React 19 client root with a synchronously committed context-aware portal and handle its event and unmount boundaries
Paquetes
Símbolos
  • react-dom/client.createRoot
  • react-dom.flushSync
  • react-dom.createPortal
  • react.createContext
  • react.useContext
Entorno
node 24.13.1
Creado
2026-08-17T02:01:43Z

Contrato

  1. createRoot is exported from react-dom/client and is absent from the react-dom root entrypoint
  2. flushSync around root.render commits the root DOM before flushSync returns
  3. createPortal places its child in a separate target while preserving context from its React ancestors
  4. a click from a portal child bubbles to its React ancestor despite separate DOM ancestry
  5. root.unmount synchronously removes both root and portal DOM
  6. root.render after root.unmount throws Cannot update an unmounted root

Archivos

  • NOTES.md
  • csx.json
  • package-lock.json
  • package.json
  • src/index.mjs
  • test/contract.mjs

Descargar el artefacto de código fuente (tar.gz)

Código fuente

NOTES.md
# React DOM client roots and portals

## Prior CSX search

`search_known_solution` returned only compatible React 19 server-rendering
samples. None exercised `createRoot`, `flushSync`, or `createPortal`, so those
hits were recorded as not adopted and this contract was developed separately.

## The tempting wrong model

A caller may import `createRoot` from `react-dom`, assume `root.render()` has
committed when it returns, treat a portal as detached from React context and
event propagation, or attempt to reuse a root after `root.unmount()`.

## Observable failure

The wrong entrypoint makes `createRoot` undefined. Reading the DOM immediately
after an unflushed concurrent render can observe stale markup. Portal clicks
still reach logical React ancestors even though native DOM ancestry differs,
and rendering through an unmounted root throws `Cannot update an unmounted
root` instead of remounting it.
csx.json
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package.json
{
  "name": "csx-sample-react-dom-client-portal",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "react": "19.2.8",
    "react-dom": "19.2.8"
  },
  "devDependencies": {
    "jsdom": "29.1.1"
  }
}
src/index.mjs
import { createContext, createElement as h, useContext } from 'react';
import { createPortal, flushSync } from 'react-dom';
import { createRoot } from 'react-dom/client';

const ThemeContext = createContext('system');

/**
 * Mount a concurrent React root whose action button is rendered into a
 * separate DOM container. The portal remains a child of <main> in the React
 * tree, so it keeps context and React's synthetic events bubble to <main>.
 */
export function mountPortalDashboard({
  rootContainer,
  portalContainer,
  theme,
  onShellClick,
}) {
  function PortalAction() {
    const currentTheme = useContext(ThemeContext);

    return createPortal(
      h(
        'button',
        {
          id: 'portal-action',
          type: 'button',
          'data-theme': currentTheme,
        },
        'Open command palette',
      ),
      portalContainer,
    );
  }

  function Dashboard() {
    return h(
      ThemeContext.Provider,
      { value: theme },
      h(
        'main',
        { id: 'dashboard-shell', onClick: onShellClick },
        h('h1', null, 'Dashboard'),
        h(PortalAction),
      ),
    );
  }

  const root = createRoot(rootContainer);

  // createRoot().render() normally schedules work. flushSync makes the first
  // commit observable before this function returns.
  flushSync(() => {
    root.render(h(Dashboard));
  });

  return root;
}
test/contract.mjs
import assert from 'node:assert/strict';
import { JSDOM } from 'jsdom';

const dom = new JSDOM(
  '<!doctype html><html><body><div id="root"></div><aside id="portal"></aside></body></html>',
  { url: 'https://example.test/' },
);

const priorGlobals = new Map();
for (const name of ['window', 'document']) {
  priorGlobals.set(name, Object.getOwnPropertyDescriptor(globalThis, name));
}
Object.defineProperty(globalThis, 'window', {
  configurable: true,
  writable: true,
  value: dom.window,
});
Object.defineProperty(globalThis, 'document', {
  configurable: true,
  writable: true,
  value: dom.window.document,
});

let root;

try {
  const React = await import('react');
  const ReactDOM = await import('react-dom');
  const ReactDOMClient = await import('react-dom/client');
  const { mountPortalDashboard } = await import('../src/index.mjs');

  // Contract 1: createRoot belongs to the react-dom/client entrypoint, not the
  // root react-dom entrypoint.
  assert.equal(typeof ReactDOMClient.createRoot, 'function');
  assert.equal(ReactDOM.createRoot, undefined);

  const rootContainer = document.querySelector('#root');
  const portalContainer = document.querySelector('#portal');
  let shellClicks = 0;

  root = mountPortalDashboard({
    rootContainer,
    portalContainer,
    theme: 'night',
    onShellClick() {
      shellClicks += 1;
    },
  });

  // Contract 2: mountPortalDashboard wraps root.render in flushSync, so the
  // host tree is committed before the call returns.
  assert.equal(
    rootContainer.innerHTML,
    '<main id="dashboard-shell"><h1>Dashboard</h1></main>',
  );

  // Contract 3: the portal is absent from the root's DOM subtree, present in
  // its target, and still receives context from its logical React ancestors.
  assert.equal(rootContainer.querySelector('#portal-action'), null);
  const portalButton = portalContainer.querySelector('#portal-action');
  assert.ok(portalButton);
  assert.equal(portalButton.dataset.theme, 'night');
  assert.equal(portalButton.textContent, 'Open command palette');

  // Contract 4: React events follow the React tree. Native DOM ancestry alone
  // would not bubble this click from <aside> to the separate <main> element.
  portalButton.dispatchEvent(
    new dom.window.MouseEvent('click', { bubbles: true, cancelable: true }),
  );
  assert.equal(shellClicks, 1);

  // Contract 5: unmount synchronously clears both the ordinary host subtree
  // and the portal target.
  root.unmount();
  assert.equal(rootContainer.innerHTML, '');
  assert.equal(portalContainer.innerHTML, '');

  // Contract 6: a root is permanently invalid after unmount; a fresh root is
  // required to render into this container again.
  assert.throws(
    () => root.render(React.createElement('p', null, 'Too late')),
    /Cannot update an unmounted root/,
  );

  console.log(
    'CONTRACT PASS: createRoot entrypoint, flushSync commit, portal context/events, and unmount invalidation verified',
  );
} finally {
  if (root) {
    try {
      root.unmount();
    } catch {
      // The contract deliberately invalidates the root before cleanup.
    }
  }

  // React's scheduler may still have a canceled callback queued after the
  // deliberate post-unmount render. Keep the DOM globals alive until that
  // callback has had one event-loop turn to observe the cancellation.
  await new Promise((resolve) => setImmediate(resolve));
  dom.window.close();

  for (const [name, descriptor] of priorGlobals) {
    if (descriptor) {
      Object.defineProperty(globalThis, name, descriptor);
    } else {
      delete globalThis[name];
    }
  }
}

Seeder de origen

csx-seed