class RuboCop::Cop::RSpec::SubjectStub

def expectation?(node)
  return if all_matcher?(node)
  receive_message?(node)
end

def find_subject(node, parent: nil, &block)
  subject(node) { |name| yield(name, parent) }
  node.each_child_node do |child|
    find_subject(child, parent: node, &block)
  end
end

def find_subject_expectation(node, subject_name, &block)
  # Do not search node if it is an example group with its own subject.
  return if example_group?(node) && redefines_subject?(node)
  # Yield the current node if it is a message expectation.
  yield(node) if message_expectation?(node, subject_name)
  # Recurse through node's children looking for a message expectation.
  node.each_child_node do |child|
    find_subject_expectation(child, subject_name, &block)
  end
end

def find_subject_stub(node, &block)
  find_subject(node) do |subject_name, context|
    find_subject_expectation(context, subject_name, &block)
  end
end

def on_block(node)
  return unless example_group?(node)
  find_subject_stub(node) do |stub|
    add_offense(stub, location: :expression)
  end
end

def redefines_subject?(node)
  node.each_child_node.any? do |child|
    subject(child) || redefines_subject?(child)
  end
end