Fix respecting a class when it already exists

.rubocop.yml

@@ -6,6 +6,10 @@ AllCops:
 Lint/ConstantDefinitionInBlock:
   Enabled: false
 
+Lint/Void:
+  Exclude:
+    - spec/ar2dto/has_dto_spec.rb
+
 Layout/LineLength:
   Max: 120
 

ar2dto.gemspec

@@ -30,4 +30,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rspec", "~> 3.9.0"
   spec.add_development_dependency "rubocop", "~> 1.28.2"
   spec.add_development_dependency "sqlite3", "~> 1.4.2"
+  spec.add_development_dependency "zeitwerk", "~> 2.6.0"
 end

lib/ar2dto/has_dto.rb

@@ -15,9 +15,11 @@ def has_dto(options = {})
         include ::AR2DTO::HasDTO::InstanceMethods
         ar2dto.setup_config(options)
 
-        return if ar2dto.namespace.const_defined?(ar2dto.class_name)
-
-        ar2dto.namespace.const_set(ar2dto.class_name, AR2DTO::DTO[self])
+        begin
+          ar2dto.namespaced_class_name.constantize
+        rescue NameError
+          ar2dto.namespace.const_set(ar2dto.class_name, AR2DTO::DTO[self])
+        end
       end
 
       # @api public

spec/ar2dto/has_dto_spec.rb

@@ -2,17 +2,23 @@
 
 RSpec.describe ".has_dto" do
   it "creates a new DTO class" do
+    User # autoload class
+
     expect(Object.const_defined?("UserDTO")).to be true
 
     expect(UserDTO.superclass).to eq AR2DTO::DTO
   end
 
   it "creates the new DTO class in the correct namespace" do
+    Shop::Order # autoload class
+
     expect(Shop.const_defined?("OrderDTO")).to be true
   end
 
   context "when the class already exists" do
     it "does not create a new class" do
+      Person # autoload class
+
       expect(Object.const_defined?("PersonDTO")).to be true
 
       expect(PersonDTO.superclass).to_not eq AR2DTO::DTO

spec/spec_helper.rb

@@ -10,11 +10,11 @@
 
 require "support/active_model"
 require "support/schema"
-require "support/fixtures/car"
-require "support/fixtures/person_dto"
-require "support/fixtures/person"
-require "support/fixtures/shop/order"
-require "support/fixtures/user"
+require "zeitwerk"
+loader = Zeitwerk::Loader.new
+loader.inflector.inflect "person_dto" => "PersonDTO"
+loader.push_dir("spec/support/fixtures")
+loader.setup
 
 RSpec.configure do |config|
   # Enable flags like --only-failures and --next-failure