//Question: if you have a function which may or may not do some async, do you use a promise for the non-async path?

//Option A: Only return promise when doing async:
function OptionA(input){
  if ( requiresQuery() ){
    var defer = Q.deferred();

    $.ajax()...
    .done(function(asyncData){
      defer.resolve(asyncData);
    });
    return defer.promise;
  }

  return input * 2;
}

//Option B: Always return a promise, resolve the non-async;

function OptionB(input){
  var defer = Q.deferred();

  if ( requiresQuery() ){
    $.ajax()...
    .done(function(asyncData){
      defer.resolve(asyncData);
    });

  }
  //Return a resolved promise
  defer.resolve(nonAsyncData);
  return defer.promise;
}