microsoft/playwright · error · Error

selectors.register: "${name}" selector engine has been alrea

Error message

selectors.register: "${name}" selector engine has been already registered

What it means

Error "selectors.register: "${name}" selector engine has been already registered" thrown in microsoft/playwright.

Source

Thrown at packages/playwright-core/src/client/selectors.ts:33

 */

import { evaluationScript } from './clientHelper';
import { setTestIdAttribute } from './locator';
import { kNoTimeout } from './timeoutSettings';

import type { SelectorEngine } from './types';
import type * as api from '../../types/types';
import type * as channels from './channels';
import type { BrowserContext } from './browserContext';

export class Selectors implements api.Selectors {
  private _selectorEngines: channels.SelectorEngine[] = [];
  private _testIdAttributeName: string | undefined;
  readonly _contextsForSelectors = new Set<BrowserContext>();

  async register(name: string, script: string | (() => SelectorEngine) | { path?: string, content?: string }, options: { contentScript?: boolean } = {}): Promise<void> {
    if (this._selectorEngines.some(engine => engine.name === name))
      throw new Error(`selectors.register: "${name}" selector engine has been already registered`);

    const source = await evaluationScript(script, undefined, false);
    const selectorEngine: channels.SelectorEngine = { ...options, name, source };
    for (const context of this._contextsForSelectors)
      await context._channel.registerSelectorEngine({ selectorEngine }, kNoTimeout);
    this._selectorEngines.push(selectorEngine);
  }

  setTestIdAttribute(attributeName: string) {
    this._testIdAttributeName = attributeName;
    setTestIdAttribute(attributeName);
    for (const context of this._contextsForSelectors) {
      context._options.testIdAttributeName = attributeName;
      context._channel.setTestIdAttributeName({ testIdAttributeName: attributeName }, kNoTimeout).catch(() => {});
    }
  }

  _withSelectorOptions<T>(options: T) {

View on GitHub (pinned to c8fc3bf8d3)

When it happens

Trigger: Thrown at packages/playwright-core/src/client/selectors.ts:33 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/playwright@c8fc3bf8d3 (2026-08-12). Data as JSON: /api/errors/1d2c39828ba206e6. Report an issue: GitHub.