wc-mixin/test/web-component.test.ts

import { afterEach, describe, expect, test, vi } from 'vitest';
import {
  WebComponent,
  choice,
  disable,
  enable,
  json,
  number,
  string,
  type PropChange,
} from '../src/index.ts';

let count = 0;

/** A fresh, unused tag name. */
function nextTag(): string {
  count += 1;
  return `x-test-${count}`;
}

/** Defines `ctor` under a fresh tag name and returns it, so `new ctor()` works. */
function define<T extends CustomElementConstructor>(ctor: T): T {
  customElements.define(nextTag(), ctor);
  return ctor;
}

/** Narrows `node` to an instance of `ctor`, failing the test otherwise. */
function instance<T>(ctor: abstract new (...args: never) => T, node: unknown): T {
  if (!(node instanceof ctor)) throw new TypeError(`expected a ${ctor.name}`);
  return node;
}

afterEach(() => {
  document.body.replaceChildren();
  for (const style of document.head.querySelectorAll('style[data-wc-mixin]')) style.remove();
});

describe('props', () => {
  test('onPropChange fires once per change, from either side', () => {
    const SPEC = { props: { count: number({ default: 0 }) } } as const;
    const changes: PropChange<typeof SPEC>[] = [];
    class El extends WebComponent(SPEC) {
      override onPropChange(change: PropChange<typeof SPEC>): void {
        changes.push(change);
      }
    }
    const el = new (define(El))();
    el.count = 1;
    el.count = 1;
    el.setAttribute('count', '2');
    el.removeAttribute('count');
    expect(changes).toEqual([
      { name: 'count', value: 1, oldValue: 0 },
      { name: 'count', value: 2, oldValue: 1 },
      { name: 'count', value: 0, oldValue: 2 },
    ]);
  });

  test('parsed attributes populate props on upgrade', () => {
    class El extends WebComponent({ props: { userId: number(), ready: enable() } }) {}
    const tag = nextTag();
    document.body.innerHTML = `<${tag} user-id="7" ready></${tag}>`;
    customElements.define(tag, El);
    const el = instance(El, document.body.firstElementChild);
    expect(el.userId).toBe(7);
    expect(el.ready).toBe(true);
  });

  test('properties set before upgrade go through the accessor', () => {
    class El extends WebComponent({ props: { label: string() } }) {}
    const tag = nextTag();
    const el = document.createElement(tag);
    Object.assign(el, { label: 'early' });
    customElements.define(tag, El);
    customElements.upgrade(el);
    document.body.append(el);
    expect(Object.hasOwn(el, 'label')).toBe(false);
    expect(instance(El, el).label).toBe('early');
    expect(el.getAttribute('label')).toBe('early');
  });

  test('boolean codecs accept ="false"', () => {
    class El extends WebComponent({ props: { ready: enable(), fetch: disable() } }) {}
    const el = new (define(El))();
    el.setAttribute('ready', 'false');
    el.setAttribute('disable-fetch', 'false');
    expect(el.ready).toBe(false);
    expect(el.fetch).toBe(true);
  });

  test('choice and json', () => {
    class El extends WebComponent({
      props: { size: choice(['s', 'm', 'l'], { default: 'm' }), data: json<{ a: number }>() },
    }) {}
    const el = new (define(El))();
    el.setAttribute('size', 'l');
    expect(el.size).toBe('l');
    el.setAttribute('size', 'xl');
    expect(el.size).toBe('m');
    el.data = { a: 1 };
    expect(el.getAttribute('data')).toBe('{"a":1}');
    el.setAttribute('data', '{"a":2}');
    expect(el.data).toEqual({ a: 2 });
  });

  test('dataPrefix prefixes derived names only', () => {
    class El extends WebComponent({
      dataPrefix: true,
      props: { userId: number(), fetch: disable(), ready: enable({ attribute: 'is-ready' }) },
    }) {}
    expect(El.observedAttributes).toEqual(['data-user-id', 'data-disable-fetch', 'is-ready']);
    expect(El.attributes).toEqual({
      userId: 'data-user-id',
      fetch: 'data-disable-fetch',
      ready: 'is-ready',
    });
    const el = new (define(El))();
    el.fetch = false;
    expect(el.dataset['disableFetch']).toBe('');
  });
});

describe('shadow DOM', () => {
  test('open shadow root gets the template and adopted css', () => {
    class El extends WebComponent({
      shadow: 'open',
      template: '<p>hi</p>',
      css: 'p { color: red; }',
    }) {}
    const el = new (define(El))();
    expect(el.shadowRoot).toBe(el.root);
    expect(el.root.innerHTML).toBe('<p>hi</p>');
    expect(el.root.adoptedStyleSheets).toHaveLength(1);
    document.body.append(el);
    expect(getComputedStyle(instance(HTMLParagraphElement, el.root.querySelector('p'))).color).toBe(
      'rgb(255, 0, 0)',
    );
  });

  test('closed shadow root stays closed but is reachable via root', () => {
    class El extends WebComponent({ shadow: 'closed', template: '<p>hi</p>' }) {}
    const el = new (define(El))();
    expect(el.shadowRoot).toBeNull();
    expect(el.root).toBeInstanceOf(ShadowRoot);
    expect(el.root.mode).toBe('closed');
  });

  test('instances share one stylesheet', () => {
    class El extends WebComponent({ shadow: 'open', css: 'p {}' }) {}
    define(El);
    const a = new El();
    const b = new El();
    expect(a.root.adoptedStyleSheets[0]).toBe(b.root.adoptedStyleSheets[0]);
  });

  test('declarative shadow DOM wins over shadow/template', () => {
    class El extends WebComponent({ shadow: 'open', template: '<p>template</p>', css: 'p {}' }) {}
    const tag = nextTag();
    document.body.setHTMLUnsafe(
      `<${tag}><template shadowrootmode="closed"><p>declarative</p></template></${tag}>`,
    );
    customElements.define(tag, El);
    const el = instance(El, document.body.firstElementChild);
    expect(el.root.mode).toBe('closed');
    expect(el.root.innerHTML).toBe('<p>declarative</p>');
    expect(el.root.adoptedStyleSheets).toHaveLength(1);
  });

  test('template element is accepted', () => {
    const template = document.createElement('template');
    template.innerHTML = '<b>x</b>';
    class El extends WebComponent({ shadow: 'open', template }) {}
    const el = new (define(El))();
    expect(el.root.innerHTML).toBe('<b>x</b>');
  });
});

describe('light DOM', () => {
  test('template is appended once, on first connect', () => {
    class El extends WebComponent({ template: '<p>hi</p>' }) {}
    const el = new (define(El))();
    expect(el.root).toBe(el);
    expect(el.childNodes).toHaveLength(0);
    document.body.append(el);
    el.remove();
    document.body.append(el);
    expect(el.innerHTML).toBe('<p>hi</p>');
  });

  test('css becomes a single <style> in the head per element type', () => {
    class El extends WebComponent({ css: 'p { color: red; }', template: '<p>hi</p>' }) {}
    const tag = nextTag();
    customElements.define(tag, El);
    document.body.append(new El(), new El());
    const styles = document.head.querySelectorAll(`style[data-wc-mixin="${tag}"]`);
    expect(styles).toHaveLength(1);
    expect(
      getComputedStyle(instance(HTMLParagraphElement, document.querySelector(`${tag} p`))).color,
    ).toBe('rgb(255, 0, 0)');
  });

  test('css is adopted into an enclosing shadow root instead of the head', () => {
    class Inner extends WebComponent({ css: 'p { color: red; }', template: '<p>hi</p>' }) {}
    const tag = nextTag();
    customElements.define(tag, Inner);
    const host = document.createElement('div');
    const shadow = host.attachShadow({ mode: 'open' });
    document.body.append(host);
    shadow.append(new Inner(), new Inner());
    expect(shadow.adoptedStyleSheets).toHaveLength(1);
    expect(document.head.querySelector(`style[data-wc-mixin="${tag}"]`)).toBeNull();
    expect(getComputedStyle(instance(HTMLParagraphElement, shadow.querySelector('p'))).color).toBe(
      'rgb(255, 0, 0)',
    );
  });
});

describe('signal and events', () => {
  test('events go to handleEvent until disconnect; reconnect re-listens', () => {
    const handle = vi.fn();
    class El extends WebComponent({ events: ['click'] }) {
      override handleEvent(event: PointerEvent): void {
        handle(event.type);
      }
    }
    const el = new (define(El))();
    document.body.append(el);
    const first = el.signal;
    el.click();
    el.remove();
    expect(first.aborted).toBe(true);
    el.click();
    expect(handle).toHaveBeenCalledTimes(1);

    document.body.append(el);
    expect(el.signal).not.toBe(first);
    expect(el.signal.aborted).toBe(false);
    el.click();
    expect(handle).toHaveBeenCalledTimes(2);
  });

  test('onConnect / onDisconnect', () => {
    const calls: string[] = [];
    class El extends WebComponent({}) {
      override onConnect(): void {
        calls.push('connect');
        document.addEventListener(
          'ping',
          () => {
            calls.push('ping');
          },
          { signal: this.signal },
        );
      }
      override onDisconnect(): void {
        calls.push('disconnect');
      }
    }
    const el = new (define(El))();
    document.body.append(el);
    document.dispatchEvent(new Event('ping'));
    el.remove();
    document.dispatchEvent(new Event('ping'));
    expect(calls).toEqual(['connect', 'ping', 'disconnect']);
  });
});

describe('refs', () => {
  test('element and elements query the root live', () => {
    class El extends WebComponent({
      shadow: 'open',
      template: '<input class="name"><ul><li>a</li><li>b</li></ul>',
      element: { input: 'input.name', missing: 'button' },
      elements: { items: 'li' },
    }) {}
    const el = new (define(El))();
    expect(el.refs.input).toBe(el.root.querySelector('input'));
    expect(el.refs.missing).toBeNull();
    expect(el.refs.items.map((li) => li.textContent)).toEqual(['a', 'b']);
    instance(HTMLUListElement, el.root.querySelector('ul')).append(document.createElement('li'));
    expect(el.refs.items).toHaveLength(3);
  });
});

describe('base', () => {
  test('extends the given base class', () => {
    class Fancy extends HTMLElement {
      readonly sparkle = 'sparkle';
    }
    class El extends WebComponent({ base: Fancy, props: { glow: enable() } }) {}
    const el = new (define(El))();
    expect(el).toBeInstanceOf(Fancy);
    expect(el.sparkle).toBe('sparkle');
  });
});