facebook/react · error · Error

320

320

Error message

Expected ReactFiberErrorDialog.showErrorDialog to be a function.

What it means

This file is the Meta-internal (www) build of the react-dom client. It requires the internal ReactFiberErrorDialog module — www's error-reporting integration — and enforces at module initialization that ReactFiberErrorDialogWWW.showErrorDialog is a function. Seeing this throw means an FB-conditional build of react-dom is running where 'ReactFiberErrorDialog' does not resolve to www's implementation.

Source

Thrown at packages/react-dom/src/client/ReactDOMRootFB.js:79

  defaultOnCaughtError,
} from 'react-reconciler/src/ReactFiberReconciler';
import {LegacyRoot} from 'react-reconciler/src/ReactRootTags';
import getComponentNameFromType from 'shared/getComponentNameFromType';

import {
  current as currentOwner,
  isRendering,
} from 'react-reconciler/src/ReactCurrentFiber';

import assign from 'shared/assign';

import noop from 'shared/noop';

// Provided by www
const ReactFiberErrorDialogWWW = require('ReactFiberErrorDialog');

if (typeof ReactFiberErrorDialogWWW.showErrorDialog !== 'function') {
  throw new Error(
    'Expected ReactFiberErrorDialog.showErrorDialog to be a function.',
  );
}

function wwwOnUncaughtError(
  error: mixed,
  errorInfo: {+componentStack?: ?string},
): void {
  const componentStack =
    errorInfo.componentStack != null ? errorInfo.componentStack : '';
  const logError = ReactFiberErrorDialogWWW.showErrorDialog({
    errorBoundary: null,
    error,
    componentStack,
  });

  // Allow injected showErrorDialog() to prevent default console.error logging.
  // This enables renderers like ReactNative to better manage redbox behavior.

View on GitHub (pinned to eafeac097b)

Solutions

1. Use the public react-dom package (react-dom/client) instead of the www/FB conditional build
2. Inside the www monorepo, fix the module map so ReactFiberErrorDialog resolves to the real implementation
3. Audit bundler/Jest aliases for react-dom and ReactFiberErrorDialog and remove stale mappings
4. Reinstall dependencies to obtain a clean registry build of react-dom

Example fix

// before (webpack resolve.alias)
'react-dom': path.resolve(__dirname, 'vendor/www/ReactDOMClientFB.js'),

// after
'react-dom': false, // let the specifier resolve normally from node_modules

// Detect an internal-build leak at startup with a clear message
try {
  await import('react-dom/client');
} catch (e) {
  if (e instanceof Error && e.message.includes('ReactFiberErrorDialog')) {
    throw new Error('An internal (www) build of react-dom is installed — replace it with the public react-dom package');
  }
  throw e;
}

When it happens

Trigger: Loading the www variant of react-dom (sources under packages/react-dom/src/client/ReactDOMRootFB.js / ReactDOMClientFB.js) with module resolution that does not provide the www ReactFiberErrorDialog module — a leaked internal artifact, a bad bundler alias, or a Jest moduleNameMapper resolving that specifier to a stub.

Common situations: OSS apps accidentally pulling a Meta-internal react-dom artifact via alias or vendored copy; monorepo module maps misconfigured so the conditional 'ReactFiberErrorDialog' specifier misses; packages accidentally built from FB-conditional entry points.

Related errors

• react-dom/profiling is not supported in React Server Compone
• This module must be shimmed by a specific renderer.
• This module must be shimmed by a specific renderer.
• 62
• A React form was unexpectedly submitted. If you called form.

AI-assisted analysis of facebook/react@eafeac097b (2026-08-21). Data as JSON: /api/errors/a72f2b3c0501ecd4. Report an issue: GitHub.