chore: throw early error selector name clash (#36469)

Author: Skn0tt

packages/playwright-core/src/client/selectors.ts

@@ -34,6 +34,9 @@ export class Selectors implements api.Selectors {
   }
 
   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(this._platform, script, undefined, false);
     const selectorEngine: channels.SelectorEngine = { ...options, name, source };
     for (const context of this._contextsForSelectors)

tests/library/selectors-register.spec.ts

@@ -145,6 +145,11 @@ it('should handle errors', async ({ playwright, browser }) => {
   await page.close();
 });
 
+it('should throw "already registered" error when registering', { annotation: { type: 'issue', description: 'https://github.com/microsoft/playwright/issues/36467' } }, async ({ playwright }) => {
+  await playwright.selectors.register('alreadyRegistered', createTagSelector);
+  await expect(playwright.selectors.register('alreadyRegistered', createTagSelector)).rejects.toThrowError('selectors.register: "alreadyRegistered" selector engine has been already registered');
+});
+
 it('should not rely on engines working from the root', async ({ playwright, browser }) => {
   const page = await browser.newPage();
   const createValueEngine = () => ({