module Rake #################################################################### # InvocationChain tracks the chain of task invocations to detect # circular dependencies. class InvocationChain def initialize(value, tail) @value = value @tail = tail end def member?(obj) @value == obj || @tail.member?(obj) end def append(value) if member?(value) fail RuntimeError, "Circular dependency detected: #{to_s} => #{value}" end self.class.new(value, self) end def to_s "#{prefix}#{@value}" end def self.append(value, chain) chain.append(value) end private def prefix "#{@tail.to_s} => " end class EmptyInvocationChain def member?(obj) false end def append(value) InvocationChain.new(value, self) end def to_s "TOP" end end EMPTY = EmptyInvocationChain.new end end