# frozen_string_literal: true module Rake # InvocationChain tracks the chain of task invocations to detect # circular dependencies. class InvocationChain < LinkedList # Is the invocation already in the chain? def member?(invocation) head == invocation || tail.member?(invocation) end # Append an invocation to the chain of invocations. It is an error # if the invocation already listed. def append(invocation) if member?(invocation) fail RuntimeError, "Circular dependency detected: #{to_s} => #{invocation}" end conj(invocation) end # Convert to string, ie: TOP => invocation => invocation def to_s "#{prefix}#{head}" end # Class level append. def self.append(invocation, chain) chain.append(invocation) end private def prefix "#{tail} => " end # Null object for an empty chain. class EmptyInvocationChain < LinkedList::EmptyLinkedList @parent = InvocationChain def member?(obj) false end def append(invocation) conj(invocation) end def to_s "TOP" end end EMPTY = EmptyInvocationChain.new end end