1 files changed, 29 insertions, 10 deletions
diff --git a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
index 67e18d692d..9678300003 100644
--- a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
@@ -13,6 +13,7 @@ module ActiveRecord
           @updated = true
         end
 
+        set_inverse_instance(record, @owner)
         loaded
         record
       end
@@ -22,19 +23,37 @@ module ActiveRecord
       end
 
       private
+
+        # NOTE - for now, we're only supporting inverse setting from belongs_to back onto
+        # has_one associations.
+        def we_can_set_the_inverse_on_this?(record)
+          @reflection.has_inverse? && @reflection.polymorphic_inverse_of(record.class).macro == :has_one
+        end
+
+        def set_inverse_instance(record, instance)
+          return if record.nil? || !we_can_set_the_inverse_on_this?(record)
+          inverse_relationship = @reflection.polymorphic_inverse_of(record.class)
+          unless inverse_relationship.nil?
+            record.send(:"set_#{inverse_relationship.name}_target", instance)
+          end
+        end
+
         def find_target
           return nil if association_class.nil?
 
-          if @reflection.options[:conditions]
-            association_class.find(
-              @owner[@reflection.primary_key_name],
-              :select     => @reflection.options[:select],
-              :conditions => conditions,
-              :include    => @reflection.options[:include]
-            )
-          else
-            association_class.find(@owner[@reflection.primary_key_name], :select => @reflection.options[:select], :include => @reflection.options[:include])
-          end
+          target =
+            if @reflection.options[:conditions]
+              association_class.find(
+                @owner[@reflection.primary_key_name],
+                :select     => @reflection.options[:select],
+                :conditions => conditions,
+                :include    => @reflection.options[:include]
+              )
+            else
+              association_class.find(@owner[@reflection.primary_key_name], :select => @reflection.options[:select], :include => @reflection.options[:include])
+            end
+          set_inverse_instance(target, @owner) if target
+          target
         end
 
         def foreign_key_present