feat: Add extendLocator to extend locators with custom properties and functions

[foxable]

Adds extendLocator, which extends a Playwright Locator with custom properties and functions while retaining the full Locator API. The extended locator can still be used for actions, combined with other locators via and()/or() and passed to expect. Overriding members of Locator is rejected at the type level. The new ExtendedLocator type is exported as well.

Example

import { extendLocator, roleLocators } from "@cronn/playwright-utils";
import { expect, test } from "@playwright/test";

test("selects a date", async ({ page }) => {
  const { textbox } = roleLocators(page);

  const datePicker = extendLocator(textbox("Date"), (locator) => ({
    async selectDate(date: Date) {
      await locator.fill(date.toISOString().slice(0, 10));
    },
  }));

  await datePicker.selectDate(new Date("2026-10-02"));

  await expect(datePicker).toHaveValue("2026-10-02");
});

[changeset-bot]

🦋 Changeset detected

Latest commit: c5f1390

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@cronn/playwright-utils	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR