Writing Decorators

function logMethod<This, Args extends any[], Return>(
  value: (this: This, ...args: Args) => Return,
  context: ClassMethodDecoratorContext
): (this: This, ...args: Args) => Return {
  return function (this: This, ...args: Args) {
    console.log(`calling ${context.name.toString()}`);
    const val = value.call(this, ...args);
    if (isPromise(val)) {
      val.then((p: unknown) => {
        console.log(`called ${context.name.toString()}: ${p}`);
        return p;
      });
    } else {
      console.log(`called ${context.name.toString()}: ${val}`);
    }

    return val;
  };
}