Function makePropDecorator

packages/core/src/util/decorators.ts:149–199

(
  name: string,
  props?: (...args: any[]) => any,
  parentClass?: any,
  additionalProcessing?: (target: any, name: string, ...args: any[]) => void,
)

}

export function makePropDecorator(
  name: string,
  props?: (...args: any[]) => any,
  parentClass?: any,
  additionalProcessing?: (target: any, name: string, ...args: any[]) => void,
): any {
  return noSideEffects(() => {
    const metaCtor = makeMetadataCtor(props);

    function PropDecoratorFactory(
      this: unknown | typeof PropDecoratorFactory,
      ...args: any[]
    ): any {
      if (this instanceof PropDecoratorFactory) {
        metaCtor.apply(this, args);
        return this;
      }

      const decoratorInstance = new (<any>PropDecoratorFactory)(...args);

      function PropDecorator(target: any, name: string) {
        // target is undefined with standard decorators. This case is not supported and will throw
        // if this decorator is used in JIT mode with standard decorators.
        if (target === undefined) {
          throw new Error('Standard Angular field decorators are not supported in JIT mode.');
        }

        const constructor = target.constructor;
        // Use of Object.defineProperty is important because it creates a non-enumerable property
        // which prevents the property from being copied during subclassing.
        const meta = constructor.hasOwnProperty(PROP_METADATA)
          ? (constructor as any)[PROP_METADATA]
          : Object.defineProperty(constructor, PROP_METADATA, {value: {}})[PROP_METADATA];
        meta[name] = (meta.hasOwnProperty(name) && meta[name]) || [];
        meta[name].unshift(decoratorInstance);

        if (additionalProcessing) additionalProcessing(target, name, ...args);
      }

      return PropDecorator;
    }

    if (parentClass) {
      PropDecoratorFactory.prototype = Object.create(parentClass.prototype);
    }

    PropDecoratorFactory.prototype.ngMetadataName = name;
    (<any>PropDecoratorFactory).annotationCls = PropDecoratorFactory;
    return PropDecoratorFactory;
  });
}