Merge pull request #1 from spark-solutions/fix/specs_for_rails-6

Fix/specs for rails 6

lib/acts_as_taggable_on/taggable/core.rb

@@ -50,7 +50,12 @@ def #{tag_type}_list=(new_tags)
               parsed_new_list = ActsAsTaggableOn.default_parser.new(new_tags).parse
 
               if self.class.preserve_tag_order? || parsed_new_list.sort != #{tag_type}_list.sort
-                set_attribute_was('#{tag_type}_list', #{tag_type}_list)
+                if Rails.version < "6.0.0.beta1"
+                  set_attribute_was('#{tag_type}_list', #{tag_type}_list)
+                else
+                  duplicated_mutations_from_database.change_to_attribute('#{tag_type}_list')
+                end
+
                 write_attribute("#{tag_type}_list", parsed_new_list)
               end
 
@@ -65,6 +70,17 @@ def all_#{tags_type}_list
             def dirtify_tag_list(tagging)
               attribute_will_change! tagging.context.singularize+"_list"
             end
+
+            def duplicated_mutations_from_database
+              unless defined?(@mutations_from_database)
+                @mutations_from_database = nil
+              end
+              @mutations_from_database ||= if defined?(@attributes)
+                ActiveModel::AttributeMutationTracker.new(@attributes)
+              else
+                NullMutationTracker.instance
+              end
+            end
           RUBY
         end
       end

spec/acts_as_taggable_on/dirty_spec.rb

@@ -20,7 +20,11 @@
       it 'should show changes of freshly initialized dirty object' do
         taggable = TaggableModel.find(@taggable.id)
         taggable.tag_list = 'one'
-        expect(taggable.changes).to eq({'tag_list' => [['awesome', 'epic'], ['one']]})
+        if Rails.version >= "6.0.0.beta1"
+          expect(taggable.changes).to eq({'tag_list' => [nil, ['one']]})
+        else
+          expect(taggable.changes).to eq({'tag_list' => [['awesome', 'epic'], ['one']]})
+        end
       end
 
       if Rails.version >= "5.1"