This error is generated when a callback generated by defer
is called more than once. In your case, it could be that Profile.getByName
is calling its callback twice (or more). This warning almost always indicates an error in my experience.
You can disable this warning if you create a callback from a Rendezvous and explicitly make it a "multi" callback. Otherwise, it only makes sense to have the return from defer
give you a one-shot callback.
More info here: https://github.com/maxtaco/coffee-script/blob/iced/iced.md#icedrendezvousidimultidefer-slots
A small note on terminology: in IcedCoffeeScript, a callback generated by defer
is known as a "deferral" in error messages and the documentation.