Move constructor to definition

lib/factory_girl/definition.rb

@@ -10,7 +10,7 @@ def initialize(name = nil, base_traits = [])
       @to_create         = ->(instance) { instance.save! }
       @base_traits       = base_traits
       @additional_traits = []
-      @constructor       = nil
+      @constructor       = default_constructor
     end
 
     delegate :declare_attribute, to: :declarations
@@ -56,8 +56,16 @@ def define_constructor(&block)
       @constructor = block
     end
 
+    def custom_constructor?
+      @constructor != default_constructor
+    end
+
     private
 
+    def default_constructor
+      @default_constructor ||= -> { new }
+    end
+
     def base_traits
       @base_traits.map { |name| trait_by_name(name) }
     end

lib/factory_girl/factory.rb

@@ -34,7 +34,7 @@ def run(build_strategy, overrides, &block)
       strategy = StrategyCalculator.new(build_strategy).strategy.new
 
       evaluator = evaluator_class.new(build_class, strategy, overrides.symbolize_keys)
-      attribute_assigner = AttributeAssigner.new(evaluator, build_class, &instance_builder)
+      attribute_assigner = AttributeAssigner.new(evaluator, build_class, &constructor)
 
       evaluation = Evaluation.new(attribute_assigner, to_create)
       evaluation.add_observer(CallbacksObserver.new(callbacks, evaluator))
@@ -118,7 +118,12 @@ def callbacks
     end
 
     def constructor
-      @constructor ||= @definition.constructor || parent.constructor
+      @constructor ||=
+        if @definition.custom_constructor?
+          @definition.constructor
+        else
+          parent.constructor
+        end
     end
 
     private
@@ -135,11 +140,6 @@ def parent
       end
     end
 
-    def instance_builder
-      build_class = self.build_class
-      constructor || -> { build_class.new }
-    end
-
     def initialize_copy(source)
       super
       @definition = @definition.clone