ECMAScript Stage 3 Methodendekorator für Parameter-Validierung

function ValidateNonEmpty<This, Args extends [string, ...unknown[]], Return>(
  target: (this: This, ...args: Args) => Return,
  context: ClassMethodDecoratorContext<This, (this: This, ...args: Args) => Return>
) {
  const methodName = String(context.name);
  return function (this: This, ...args: Args): Return {
    if (!args[0] || args[0].trim().length === 0) {
      throw new Error(`Invalid argument in ${methodName}: string must not be empty`);
    }
    return target.apply(this, args);
  };
}
 
class UserRegistry {
  @ValidateNonEmpty
  registerUser(username: string, role: string): string {
    return `Registered ${username} as ${role}`;
  }
}