wc-mixin/test/types.test-d.ts

import { describe, expectTypeOf, test } from 'vitest';
import {
  WebComponent,
  choice,
  disable,
  enable,
  json,
  number,
  string,
  type AttributesOf,
  type Kebab,
  type PropChange,
  type RefType,
} from '../src/index.ts';

const SPEC = {
  shadow: 'open',
  events: ['click', 'keydown'],
  element: { input: 'input.name', go: 'form > button#go', thing: '.thing' },
  elements: { items: 'ul li' },
  props: {
    userId: number(),
    userName: string(),
    min: number({ default: 1 }),
    max: number({ default: 10 }),
    ready: enable({ attribute: 'is-ready' }),
    fetch: disable(),
    size: choice(['s', 'm', 'l'], { default: 'm' }),
    points: json<[number, number][]>({ default: [] }),
  },
} as const;

class Example extends WebComponent(SPEC) {}

describe('kebab', () => {
  test('mirrors the runtime conversion', () => {
    expectTypeOf<Kebab<'userId'>>().toEqualTypeOf<'user-id'>();
    expectTypeOf<Kebab<'aBC'>>().toEqualTypeOf<'a-b-c'>();
    expectTypeOf<Kebab<'x2y'>>().toEqualTypeOf<'x2y'>();
  });
});

describe('attributes', () => {
  test('observedAttributes is the exact union', () => {
    type Expected =
      | 'user-id'
      | 'user-name'
      | 'min'
      | 'max'
      | 'is-ready'
      | 'disable-fetch'
      | 'size'
      | 'points';
    expectTypeOf(Example.observedAttributes).toEqualTypeOf<readonly Expected[]>();
    expectTypeOf<AttributesOf<typeof Example>>().toEqualTypeOf<Expected>();
    expectTypeOf<AttributesOf<typeof SPEC>>().toEqualTypeOf<Expected>();
  });

  test('attributes maps each key to its attribute', () => {
    expectTypeOf(Example.attributes.fetch).toEqualTypeOf<'disable-fetch'>();
    expectTypeOf(Example.attributes.ready).toEqualTypeOf<'is-ready'>();
  });

  test('dataPrefix applies only to derived names', () => {
    const Base = WebComponent({
      dataPrefix: true,
      props: { userId: number(), fetch: disable(), ready: enable({ attribute: 'is-ready' }) },
    });
    expectTypeOf<AttributesOf<typeof Base>>().toEqualTypeOf<
      'data-user-id' | 'data-disable-fetch' | 'is-ready'
    >();
  });

  test('inline specs infer without `as const`', () => {
    const Base = WebComponent({ props: { fooBar: string({ attribute: 'fb' }), bazQux: number() } });
    expectTypeOf<AttributesOf<typeof Base>>().toEqualTypeOf<'fb' | 'baz-qux'>();
  });
});

describe('prop values', () => {
  test('defaults decide optionality', () => {
    const el = new Example();
    expectTypeOf(el.userId).toEqualTypeOf<number | undefined>();
    expectTypeOf(el.userName).toEqualTypeOf<string | undefined>();
    expectTypeOf(el.min).toEqualTypeOf<number>();
    expectTypeOf(el.ready).toEqualTypeOf<boolean>();
    expectTypeOf(el.fetch).toEqualTypeOf<boolean>();
    expectTypeOf(el.size).toEqualTypeOf<'s' | 'm' | 'l'>();
    expectTypeOf(el.points).toEqualTypeOf<[number, number][]>();
    const Named = WebComponent({
      props: { data: json<{ a: number }, 'payload'>({ attribute: 'payload' }) },
    });
    expectTypeOf(new Named().data).toEqualTypeOf<{ a: number } | undefined>();
    expectTypeOf<AttributesOf<typeof Named>>().toEqualTypeOf<'payload'>();
  });

  test('props are writable and type-checked', () => {
    const el = new Example();
    el.min = 2;
    el.userId = undefined;
    // @ts-expect-error -- wrong type
    el.min = '2';
    // @ts-expect-error -- not in the choice list
    el.size = 'xl';
  });

  test('onPropChange receives a discriminated union', () => {
    expectTypeOf<PropChange<typeof Example>>().toEqualTypeOf<PropChange<typeof SPEC>>();
    class Watcher extends WebComponent(SPEC) {
      override onPropChange(change: PropChange<typeof SPEC>): void {
        if (change.name === 'min') expectTypeOf(change.value).toEqualTypeOf<number>();
        if (change.name === 'userId')
          expectTypeOf(change.oldValue).toEqualTypeOf<number | undefined>();
      }
    }
    expectTypeOf<Watcher>().toExtend<HTMLElement>();
  });
});

describe('members', () => {
  test('root is a ShadowRoot when shadow is set', () => {
    expectTypeOf(new Example().root).toEqualTypeOf<ShadowRoot>();
    const Light = WebComponent({});
    expectTypeOf(new Light().root).toEqualTypeOf<ShadowRoot | HTMLElement>();
  });

  test('handleEvent gets the union of listed events', () => {
    expectTypeOf<Parameters<Example['handleEvent']>[0]>().toEqualTypeOf<
      HTMLElementEventMap['click' | 'keydown']
    >();
  });

  test('refs are typed from their selectors', () => {
    const { refs } = new Example();
    expectTypeOf(refs.input).toEqualTypeOf<HTMLInputElement | null>();
    expectTypeOf(refs.go).toEqualTypeOf<HTMLButtonElement | null>();
    expectTypeOf(refs.thing).toEqualTypeOf<Element | null>();
    expectTypeOf(refs.items).toEqualTypeOf<HTMLLIElement[]>();
    expectTypeOf<RefType<'svg circle.dot'>>().toEqualTypeOf<SVGCircleElement>();
    expectTypeOf<RefType<'input:checked'>>().toEqualTypeOf<HTMLInputElement>();
  });

  test('still an HTMLElement', () => {
    expectTypeOf(new Example()).toExtend<HTMLElement>();
    expectTypeOf(new Example().signal).toEqualTypeOf<AbortSignal>();
  });
});

describe('conflicts', () => {
  test('prop names colliding with HTMLElement members are rejected', () => {
    // @ts-expect-error -- `title` is on HTMLElement
    WebComponent({ props: { title: string() } });
    // @ts-expect-error -- `hidden` is on HTMLElement
    WebComponent({ props: { hidden: enable() } });
  });

  test('prop names colliding with mixin members are rejected', () => {
    // @ts-expect-error -- `signal` is a mixin member
    WebComponent({ props: { signal: string() } });
  });

  test('conflicts are checked against the base class', () => {
    class Fancy extends HTMLElement {
      sparkle = true;
    }
    // @ts-expect-error -- `sparkle` is on the base
    WebComponent({ base: Fancy, props: { sparkle: enable() } });

    const El = WebComponent({ base: Fancy, props: { glow: enable() } });
    expectTypeOf(new El().sparkle).toEqualTypeOf<boolean>();
    expectTypeOf(new El().glow).toEqualTypeOf<boolean>();
  });
});