Rails/Delegate ignores ruby 2.3 Safe Nagivation Operator

[PizzaPill]

The following line of code:

object_that_can_be_nil&.foo gets converted to delegate :foo, to: :object_that_can_be_nil, prefix: true which is not equivalent. The equivalent would be delegate :foo, to: :object_that_can_be_nil, prefix: true, allow_nil: true.

This all happens in rubocop 0.39.0 and parameter auto-correct enabled.

[jonas054]

@geniou You created that cop. Can you look into this?

[andialles]

Same thing happens here:

def foo
    bar.foo if bar
end

gets converted to delegate :foo, to: :bar without the allow_nil: true parameter

[cgriego]

One gotcha here is that allow_nil is not equivalent to &. because allow_nil checks that the receiver is not nil or if it responds to the method. So methods that nil responds to are also delegated. This is problematic, but the only handy example I have is with whiny nils.

# nil if foo is nil
def foo_id
  foo&.id
end

# RuntimeError if foo is nil and whiny nils
delegate :id, to: :foo, prefix: true, allow_nil: true