react-native-devtools-frontend/front_end/testing/DOMHelpers.ts

// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/**
 * These helpers are designed to be used when testing components or other code that renders into the DOM.
 * By using these helpers we ensure the DOM is correctly cleaned between test runs.
 *
 * Note that `resetTestDOM` is automatically run before each test (see `test_setup.ts`).
 **/

import type * as NodeText from '../ui/components/node_text/node_text.js';
import * as UI from '../ui/legacy/legacy.js';

const TEST_CONTAINER_ID = '__devtools-test-container-id';

interface RenderOptions {
  allowMultipleChildren?: boolean;
}

/**
 * Renders a given element into the DOM. By default it will error if it finds an element already rendered but this can be controlled via the options.
 **/
export function renderElementIntoDOM<E extends Element>(element: E, renderOptions: RenderOptions = {}): E {
  const container = document.getElementById(TEST_CONTAINER_ID);

  if (!container) {
    throw new Error(`renderElementIntoDOM expects to find ${TEST_CONTAINER_ID}`);
  }

  const allowMultipleChildren = Boolean(renderOptions.allowMultipleChildren);

  if (container.childNodes.length !== 0 && !allowMultipleChildren) {
    throw new Error(`renderElementIntoDOM expects the container to be empty ${container.innerHTML}`);
  }
  container.appendChild(element);
  return element;
}

function removeChildren(node: Node): void {
  while (true) {
    const {firstChild} = node;
    if (firstChild === null) {
      break;
    }
    const widget = UI.Widget.Widget.get(firstChild);
    if (widget) {
      // Child is a widget, so we have to use the Widget system to remove it from the DOM.
      widget.detach();
      continue;
    }
    // For regular children, recursively remove their children, since some of them
    // might be widgets, and only afterwards remove the child from the current node.
    removeChildren(firstChild);
    node.removeChild(firstChild);
  }
}

/**
 * Sets up the DOM for testing,
 * If not clean logs an error and cleans itself
 **/
export const setupTestDOM = async () => {
  const previousContainer = document.getElementById(TEST_CONTAINER_ID);
  if (previousContainer) {
    // This should not be reachable, unless the
    // AfterEach hook fails before cleaning the DOM.
    // Clean it here and report
    console.error('Non clean test state found!');
    await cleanTestDOM();
  }
  const newContainer = document.createElement('div');
  newContainer.id = TEST_CONTAINER_ID;

  document.body.appendChild(newContainer);
};

/**
 * Completely cleans out the test DOM to ensure it's empty for the next test run.
 * This is run automatically between tests - you should not be manually calling this yourself.
 **/
export const cleanTestDOM = async () => {
  const previousContainer = document.getElementById(TEST_CONTAINER_ID);
  if (previousContainer) {
    removeChildren(previousContainer);
    previousContainer.remove();
  }
  await raf();
};

interface Constructor<T> {
  new(...args: unknown[]): T;
}

/**
 * Asserts that all emenents of `nodeList` are at least of type `T`.
 */
export function assertElements<T extends Element>(
    nodeList: NodeListOf<Element>, elementClass: Constructor<T>): asserts nodeList is NodeListOf<T> {
  nodeList.forEach(e => assert.instanceOf(e, elementClass));
}

export function getElementWithinComponent<T extends HTMLElement, V extends Element>(
    component: T, selector: string, elementClass: Constructor<V>) {
  assert.isNotNull(component.shadowRoot);
  const element = component.shadowRoot.querySelector(selector);
  assert.instanceOf(element, elementClass);
  return element;
}

export function getElementsWithinComponent<T extends HTMLElement, V extends Element>(
    component: T, selector: string, elementClass: Constructor<V>) {
  assert.isNotNull(component.shadowRoot);
  const elements = component.shadowRoot.querySelectorAll(selector);
  assertElements(elements, elementClass);
  return elements;
}

/* Waits for the given element to have a scrollLeft property of at least desiredScrollLeft */
export function waitForScrollLeft<T extends Element>(element: T, desiredScrollLeft: number): Promise<void> {
  let lastScrollLeft = -1;
  let scrollLeftTimeout: number|null = null;

  const timeBetweenPolls = 50;

  return new Promise(resolve => {
    const pollForScrollLeft = () => {
      const newScrollLeft = element.scrollLeft;
      // If we get the same scroll value twice in a row, and it's at least what
      // we want, we're done!
      if (lastScrollLeft === newScrollLeft && newScrollLeft >= desiredScrollLeft) {
        if (scrollLeftTimeout) {
          window.clearTimeout(scrollLeftTimeout);
        }
        resolve();
        return;
      }

      lastScrollLeft = newScrollLeft;
      scrollLeftTimeout = window.setTimeout(pollForScrollLeft, timeBetweenPolls);
    };

    window.setTimeout(pollForScrollLeft, timeBetweenPolls);
  });
}

/**
 * Dispatches a mouse click event.
 */
export function dispatchClickEvent<T extends Element>(element: T, options: MouseEventInit = {}) {
  const clickEvent = new MouseEvent('click', options);
  element.dispatchEvent(clickEvent);
}

export function dispatchMouseUpEvent<T extends Element>(element: T, options: MouseEventInit = {}) {
  const clickEvent = new MouseEvent('mouseup', options);
  element.dispatchEvent(clickEvent);
}

export function dispatchBlurEvent<T extends Element>(element: T, options: FocusEventInit = {}) {
  const focusEvent = new FocusEvent('blur', options);
  element.dispatchEvent(focusEvent);
}

export function dispatchFocusEvent<T extends Element>(element: T, options: FocusEventInit = {}) {
  const focusEvent = new FocusEvent('focus', options);
  element.dispatchEvent(focusEvent);
}

export function dispatchFocusOutEvent<T extends Element>(element: T, options: FocusEventInit = {}) {
  const focusEvent = new FocusEvent('focusout', options);
  element.dispatchEvent(focusEvent);
}

/**
 * Dispatches a keydown event. Errors if the event was not dispatched successfully.
 */
export function dispatchKeyDownEvent<T extends Element>(element: T, options: KeyboardEventInit = {}) {
  const clickEvent = new KeyboardEvent('keydown', options);
  const success = element.dispatchEvent(clickEvent);
  if (!success) {
    assert.fail('Failed to trigger keydown event successfully.');
  }
}

export function dispatchInputEvent<T extends Element>(element: T, options: InputEventInit = {}) {
  const inputEvent = new InputEvent('input', options);
  element.dispatchEvent(inputEvent);
}

/**
 * Dispatches a mouse over event.
 */
export function dispatchMouseOverEvent<T extends Element>(element: T, options: MouseEventInit = {}) {
  const moveEvent = new MouseEvent('mouseover', options);
  element.dispatchEvent(moveEvent);
}
/**
 * Dispatches a mouse out event.
 */
export function dispatchMouseOutEvent<T extends Element>(element: T, options: MouseEventInit = {}) {
  const moveEvent = new MouseEvent('mouseout', options);
  element.dispatchEvent(moveEvent);
}

/**
 * Dispatches a mouse move event.
 */
export function dispatchMouseMoveEvent<T extends Element>(element: T, options: MouseEventInit = {}) {
  const moveEvent = new MouseEvent('mousemove', options);
  element.dispatchEvent(moveEvent);
}

/**
 * Dispatches a mouse leave event.
 */
export function dispatchMouseLeaveEvent<T extends Element>(element: T, options: MouseEventInit = {}) {
  const leaveEvent = new MouseEvent('mouseleave', options);
  element.dispatchEvent(leaveEvent);
}

/**
 * Dispatches a clipboard copy event.
 */
export function dispatchCopyEvent<T extends Element>(element: T, options: ClipboardEventInit = {}) {
  const copyEvent = new ClipboardEvent('copy', options);
  element.dispatchEvent(copyEvent);
}

/**
 * Dispatches a clipboard paste event.
 */
export function dispatchPasteEvent<T extends Element>(element: T, options: ClipboardEventInit = {}) {
  const pasteEvent = new ClipboardEvent('paste', options);
  element.dispatchEvent(pasteEvent);
}

/**
 * Listens to an event of an element and returns a Promise that resolves to the
 * specified event type.
 */
export function getEventPromise<T extends Event>(element: HTMLElement, eventName: string): Promise<T> {
  return new Promise<T>(resolve => {
    element.addEventListener(eventName, (event: Event) => {
      resolve(event as T);
    }, {once: true});
  });
}

export async function doubleRaf() {
  return await new Promise(resolve => requestAnimationFrame(() => requestAnimationFrame(resolve)));
}

export async function raf() {
  return await new Promise(resolve => requestAnimationFrame(resolve));
}

/**
 * It's useful to use innerHTML in the tests to have full confidence in the
 * renderer output, but Lit uses comment nodes to split dynamic from
 * static parts of a template, and we don't want our tests full of noise
 * from those.
 */
export function stripLitHtmlCommentNodes(text: string) {
  /**
   * Lit comments take the form of:
   * <!--?lit$1234?--> or:
   * <!--?-->
   * <!---->
   * And this regex matches all of them.
   */
  return text.replaceAll(/<!--(\?)?(lit\$[0-9]+\$)?-->/g, '');
}

/**
 * Returns an array of textContents.
 * Multiple consecutive newLine and space characters are removed.
 */
export function getCleanTextContentFromElements(el: ShadowRoot|HTMLElement, selector: string): string[] {
  const elements = Array.from(el.querySelectorAll(selector));
  return elements.map(element => {
    return element.textContent ? element.textContent.trim().replace(/[ \n]{2,}/g, ' ') : '';
  });
}

/**
 * Returns the text content for the first element matching the given `selector` within the provided `el`.
 * Will error if no element is found matching the selector.
 */
export function getCleanTextContentFromSingleElement(el: ShadowRoot|HTMLElement, selector: string): string {
  const element = el.querySelector(selector);
  assert.isOk(element, `Could not find element with selector ${selector}`);
  return element.textContent ? cleanTextContent(element.textContent) : '';
}

export function cleanTextContent(input: string): string {
  return input.trim().replace(/[ \n]{2,}/g, ' ');
}

export function assertNodeTextContent(component: NodeText.NodeText.NodeText, expectedContent: string) {
  assert.isNotNull(component.shadowRoot);
  const content = Array.from(component.shadowRoot.querySelectorAll('span')).map(span => span.textContent).join('');
  assert.strictEqual(content, expectedContent);
}

export function querySelectorErrorOnMissing<T extends HTMLElement = HTMLElement>(
    parent: HTMLElement, selector: string): T {
  const elem = parent.querySelector<T>(selector);
  if (!elem) {
    throw new Error(`Expected element with selector ${selector} not found.`);
  }
  return elem;
}

/**
 * Given a filename in the format "<folder>/<image.png>"
 * this function asserts that a screenshot taken from the element
 * identified by the TEST_CONTAINER_ID matches a screenshot
 * in test/interactions/goldens/linux/<folder>/<image.png>.
 *
 * Currently, it only asserts screenshots match goldens on Linux.
 * The function relies on the bindings exposed via the karma config.
 */
export async function assertScreenshot(filename: string) {
  // To avoid a lot of empty space in the screenshot.
  document.getElementById(TEST_CONTAINER_ID)!.style.width = 'fit-content';
  let frame: Window|null = window;
  while (frame) {
    frame.scrollTo(0, 0);
    frame = frame.parent !== frame ? frame.parent : null;
  }
  await raf();
  // @ts-expect-error see karma config.
  const result = await window.assertScreenshot(`#${TEST_CONTAINER_ID}`, filename);
  if (result) {
    throw new Error(result);
  }
}