Fix shared state between class instances

Use Marshal load and dump to make a deep clone.

Author: MatheusRich

.rubocop.yml

@@ -18,3 +18,5 @@ Metrics/AbcSize:
 Style/DocumentationMethod:
   Enabled: true
 
+RSpec/ExampleLength:
+  Max: 15

lib/ez_attributes.rb

@@ -26,7 +26,7 @@ def attributes(*args, **args_with_default)
     optional_args = args_with_default.map { |name, _| "#{name}: __args_with_default[:#{name}]" }
     init_args = (required_args + optional_args).join(', ')
 
-    define_method('__args_with_default', -> { args_with_default.dup })
+    define_method('__args_with_default', -> { Marshal.load(Marshal.dump(args_with_default)) })
     private :__args_with_default
 
     all_args = args + args_with_default.keys

spec/ez_attributes_spec.rb

@@ -111,4 +111,30 @@
       expect(obj.if).to eq true
     end
   end
+
+  context 'when an instance mutates state' do
+    let(:test_class) do
+      Class.new do
+        extend EzAttributes
+
+        attributes a: []
+
+        def change_attr
+          a << 1
+        end
+      end
+    end
+
+    it 'does not share state with other instances', :aggregate_failures do
+      obj1 = test_class.new
+      obj1.change_attr
+      obj1.change_attr
+
+      obj2 = test_class.new
+      obj2.change_attr
+
+      expect(obj1.a).to eq [1, 1]
+      expect(obj2.a).to eq [1]
+    end
+  end
 end