Fix for factory class naming (#366)

Changing the process of name selection for factory defining

Example:

rails g model UserMedia filename:string --force-plural
...
invoke      factory_bot
create        spec/factories/user_media.rb

it generates the correct factory naming:

FactoryBot.define do
  factory :user_media do
    filename { "MyString" }
  end
end

Fixes: #356

features/generators.feature

@@ -24,6 +24,18 @@ Feature:
       """
     And the file "test/factories/namespaced/users.rb" should contain "factory :namespaced_user, class: 'Namespaced::User' do"
 
+  Scenario: The factory_bot_rails generators create a factory file with correct naming when I use --force-plural
+    When I run `bundle exec rails generate model UserMedia filename:string --force-plural` with a clean environment
+    Then the output should contain "test/factories/user_media.rb"
+    And the file "test/factories/user_media.rb" should contain exactly:
+      """
+      FactoryBot.define do
+        factory :user_media do
+          filename { "MyString" }
+        end
+      end
+      """
+
   Scenario: The factory_bot_rails generators add a factory in the correct spot
     When I write to "test/factories.rb" with:
       """

lib/generators/factory_bot.rb

@@ -14,8 +14,12 @@ module FactoryBot
         File.expand_path(path)
       end
 
+      def factory_name
+        class_name.gsub("::", "").underscore
+      end
+
       def explicit_class_option
-        return if class_name == singular_table_name.camelize
+        return if class_name.underscore == factory_name
 
         ", class: '#{class_name}'"
       end

lib/generators/factory_bot/model/model_generator.rb

@@ -54,7 +54,7 @@ module FactoryBot
 
       def factory_definition
         <<~RUBY
-            factory :#{singular_table_name}#{explicit_class_option} do
+            factory :#{factory_name}#{explicit_class_option} do
           #{factory_attributes.gsub(/^/, '    ')}
             end