Warn when the same predicate is used in more than one property in the…

… same class

lib/active_fedora/attributes.rb

@@ -171,16 +171,23 @@ def multiple?(field)
       end
 
       def property name, properties={}, &block
+        warn_duplicate_predicates name, properties
         properties = { multiple: true }.merge(properties)
         find_or_create_defined_attribute(name, nil, properties)
         raise ArgumentError, "#{name} is a keyword and not an acceptable property name." if protected_property_name? name
         reflection = ActiveFedora::Attributes::PropertyBuilder.build(self, name, properties, &block)
-        # reflection = ActiveTriple::PropertyBuilder.build(self, name, properties, &block)
         ActiveTriples::Reflection.add_reflection self, name, reflection
       end
 
       private
 
+      def warn_duplicate_predicates new_name, new_properties
+        new_predicate = new_properties[:predicate]
+        self.properties.select{|k, existing| existing.predicate == new_predicate}.each do |key, value| 
+          ActiveFedora::Base.logger.warn "Same predicate (#{new_predicate}) used for properties #{key} and #{new_name}"
+        end
+      end
+
       def find_or_create_defined_attribute(field, dsid, args)
         delegated_attributes[field] ||= DelegatedAttribute.new(field, dsid, datastream_class_for_name(dsid), args)
       end

spec/unit/property_predicate_spec.rb

@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+describe 'Properties with the same predicate' do
+
+  let(:warningMsg) {"Same predicate (http://purl.org/dc/terms/title) used for properties title1 and title2"}
+
+  it "should warn" do
+
+    # Note that the expect test must be before the class is parsed. 
+    expect(ActiveFedora::Base.logger).to receive(:warn).with(warningMsg)
+
+    module TestModel1
+      class Book < ActiveFedora::Base
+        property :title1, predicate: ::RDF::DC.title 
+        property :title2, predicate: ::RDF::DC.title 
+      end
+    end      
+
+  end
+
+end
+
+
+describe 'Properties with different predicate' do
+
+  it "should not warn" do
+
+    # Note that the expect test must be before the class is parsed. 
+    expect(ActiveFedora::Base.logger).to_not receive(:warn)
+
+    module TestModel2
+      class Book < ActiveFedora::Base
+        property :title1, predicate: ::RDF::DC.title
+        property :title2, predicate: ::RDF::DC.creator
+      end
+    end
+
+  end
+
+end