lib/pallets/graph.rb in pallets-0.5.1 vs lib/pallets/graph.rb in pallets-0.6.0

@@ -7,19 +7,23 @@
     def initialize
       @nodes = {}
     end
 
     def add(node, dependencies)
-      @nodes[node] = dependencies
+      raise WorkflowError, "Task #{node} is already defined in this workflow. "\
+                           "Use `task '#{node}', as: 'FooBar'` to define an "\
+                           "alias and reuse task" if nodes.key?(node)
+
+      nodes[node] = dependencies
     end
 
     def parents(node)
-      @nodes[node]
+      nodes[node]
     end
 
     def empty?
-      @nodes.empty?
+      nodes.empty?
     end
 
     # Returns nodes topologically sorted, together with their order (number of
     # nodes that have to be executed prior)
     def sorted_with_order
@@ -35,15 +39,17 @@
       end
     end
 
     private
 
+    attr_reader :nodes
+
     def tsort_each_node(&block)
-      @nodes.each_key(&block)
+      nodes.each_key(&block)
     end
 
     def tsort_each_child(node, &block)
-      @nodes.fetch(node).each(&block)
+      nodes.fetch(node).each(&block)
     rescue KeyError
       raise WorkflowError, "Task #{node} is marked as a dependency but not defined"
     end
   end
 end