null.collect() returns empty list

Question

I was writing unit tests when I happened to find that in groovy the below is true

null.collect({ //Anything }) == []

I could not find the reason for this. What part of groovy is giving this behavior? I checked NullObject but that does not have this collect method. So how is this happening?

Answer 1

In groovy null has the iterator() method which returns an empty iterator. Calling collect on null is the same as null.iterator().collect({/*whatever*/}) and so this will be [].

See the comment on this bug report.