Default value lambda improvements

lib/aws-record/record/attribute.rb

@@ -53,7 +53,9 @@ def initialize(name, options = {})
         @marshaler = options[:marshaler] || DefaultMarshaler
         @persist_nil = options[:persist_nil]
         dv = options[:default_value]
-        @default_value_or_lambda = type_cast(dv) unless dv.nil?
+        unless dv.nil?
+          @default_value_or_lambda = _is_lambda?(dv) ? dv : type_cast(dv)
+        end
       end
 
       # Attempts to type cast a raw value into the attribute's type. This call
@@ -92,8 +94,8 @@ def extract(dynamodb_item)
 
       # @api private
       def default_value
-        if @default_value_or_lambda.respond_to?(:call)
-          @default_value_or_lambda.call
+        if _is_lambda?(@default_value_or_lambda)
+          type_cast(@default_value_or_lambda.call)
         else
           _deep_copy(@default_value_or_lambda)
         end
@@ -104,6 +106,10 @@ def _deep_copy(obj)
         Marshal.load(Marshal.dump(obj))
       end
 
+      def _is_lambda?(obj)
+        obj.respond_to?(:call)
+      end
+
     end
 
     # This is an identity marshaler, which performs no changes for type casting

lib/aws-record/record/item_data.rb

@@ -105,9 +105,9 @@ def build_save_hash
 
       def populate_default_values
         @model_attributes.attributes.each do |name, attribute|
-          unless attribute.default_value.nil?
+          unless (default_value = attribute.default_value).nil?
             if @data[name].nil? && @data[name].nil?
-              @data[name] = attribute.default_value
+              @data[name] = default_value
             end
           end
         end

spec/aws-record/record/attribute_spec.rb

@@ -37,6 +37,19 @@ module Record
           expect(a.default_value).to eq(5)
         end
 
+        it 'does not type_cast lambdas' do
+          m = Marshalers::DateTimeMarshaler.new
+          a = Attribute.new(:foo, marshaler: m, default_value: -> { Time.now })
+          dv = a.instance_variable_get("@default_value_or_lambda")
+          expect(dv.respond_to?(:call)).to eq(true)
+        end
+
+        it 'type casts result of calling a default_value lambda' do
+          m = Marshalers::StringMarshaler.new
+          a = Attribute.new(:foo, marshaler: m, default_value: -> { :huzzah })
+          expect(a.default_value).to be_a(String)
+        end
+
         it 'uses a deep copy' do
           a = Attribute.new(:foo, default_value: {})
           a.default_value['greeting'] = 'hi'