GoogleChrome/lighthouse · error

UIStrings exported but no definition found: ${relativeToRoot

Error message

UIStrings exported but no definition found: ${relativeToRootPath}

What it means

Thrown during collection when a module exports `UIStrings` (or `default.UIStrings`) at runtime, but the UISTRINGS_REGEX pattern cannot find a matching definition in the raw file text. This means the export exists dynamically but the static text-based parser cannot locate the definition to extract messages.

Source

Thrown at core/scripts/i18n/collect-strings.js:582

  const files = glob.sync(globPattern, {
    cwd: LH_ROOT,
    ignore: ignoredPathComponents,
  });

  for (const relativeToRootPath of files) {
    const absolutePath = path.join(LH_ROOT, relativeToRootPath);
    if (!process.env.CI) console.log('Collecting from', relativeToRootPath);

    const content = fs.readFileSync(absolutePath, 'utf8');
    const exportVars = await import(pathToFileURL(absolutePath).href);
    const regexMatch = content.match(UISTRINGS_REGEX);
    const exportedUIStrings = exportVars.UIStrings || exportVars.default?.UIStrings;

    if (!regexMatch) {
      // No UIStrings found in the file text or exports, so move to the next.
      if (!exportedUIStrings) continue;

      throw new Error('UIStrings exported but no definition found: ' + relativeToRootPath);
    }

    if (!exportedUIStrings) {
      throw new Error('UIStrings defined in file but not exported');
    }

    // just parse the UIStrings substring to avoid ES version issues, save time, etc
    const justUIStrings = 'const ' + regexMatch[0];
    const parsedMessages = parseUIStrings(justUIStrings, exportedUIStrings);

    for (const [key, parsed] of Object.entries(parsedMessages)) {
      const {message, description, examples} = parsed;
      const converted = convertMessageToCtc(message, examples);

      // Don't include placeholders if there are none.
      const placeholders = Object.keys(converted.placeholders).length === 0 ?
          undefined :
          converted.placeholders;

View on GitHub (pinned to 9515cd4e58)

Solutions

1. Define UIStrings as a top-level `const UIStrings = {...}` literal in the same file that exports it.
2. Ensure the export uses `export const UIStrings` or `export {UIStrings}` referencing a directly-defined const matching UISTRINGS_REGEX.
3. Avoid re-exporting UIStrings from another module in files scanned by collect-strings.

Example fix

// before
export {UIStrings} from './strings.js'
// after
const UIStrings = {
  /** @description My message */
  myMessage: 'My message',
};
export {UIStrings};

const UISTRINGS_REGEX = /(?:const|let|var)\s+UIStrings\s*=\s*\{/;
function hasInlineUIStringsDefinition(fileText) {
  return UISTRINGS_REGEX.test(fileText);
}

When it happens

Trigger: Exporting UIStrings via a computed property, re-export from another module, dynamic spread, or any pattern that defeats the simple regex-based text scan — e.g. `export {UIStrings} from './other'` or `module.exports.UIStrings`.

Common situations: Refactoring how UIStrings is exported; using re-exports instead of inline definitions; CommonJS-style exports in a file the scanner expects ESM from.

Related errors

• UIStrings defined in file but not exported
• unsupported JSDoc comment: ${JSON.stringify(comment)}
• Incorrectly formatted @example: "${rawExample}"
• [${err.message}] Did not find the expected syntax in message
• Content cannot appear outside plural or select ICU messages.

AI-assisted analysis of GoogleChrome/lighthouse@9515cd4e58 (2026-08-13). Data as JSON: /api/errors/3739e3cea719bce9. Report an issue: GitHub.