Show default parent classes for generators in help texts

Print default parent class for controller, job, and model generators.

Before:

[--parent=PARENT]               # The parent class for the generated job

After:

[--parent=PARENT]               # The parent class for the generated job
                                # Default: ApplicationJob

activejob/lib/rails/generators/job/job_generator.rb

@@ -7,7 +7,7 @@ module Rails # :nodoc:
     class JobGenerator < Rails::Generators::NamedBase # :nodoc:
       class_option :queue, type: :string, default: "default", desc: "The queue name for the generated job"
 
-      class_option :parent, type: :string, desc: "The parent class for the generated job"
+      class_option :parent, type: :string, default: "ApplicationJob", desc: "The parent class for the generated job"
 
       check_class_collision suffix: "Job"
 
@@ -28,16 +28,8 @@ module Rails # :nodoc:
       end
 
       private
-        def parent
-          options[:parent]
-        end
-
         def parent_class_name
-          if parent
-            parent
-          else
-            "ApplicationJob"
-          end
+          options[:parent]
         end
 
         def file_name

activerecord/lib/rails/generators/active_record/model/model_generator.rb

@@ -11,7 +11,7 @@ module ActiveRecord
 
       class_option :migration, type: :boolean
       class_option :timestamps, type: :boolean
-      class_option :parent, type: :string, desc: "The parent class for the generated model"
+      class_option :parent, type: :string, default: "ApplicationRecord", desc: "The parent class for the generated model"
       class_option :indexes, type: :boolean, default: true, desc: "Add indexes for references and belongs_to columns"
       class_option :primary_key_type, type: :string, desc: "The type for primary key"
       class_option :database, type: :string, aliases: %i(--db), desc: "The database for your model's migration. By default, the current environment's primary database is used."
@@ -24,7 +24,7 @@ module ActiveRecord
       end
 
       def create_model_file
-        generate_abstract_class if database && !parent
+        generate_abstract_class if database && !custom_parent?
         template "model.rb", File.join("app/models", class_path, "#{file_name}.rb")
       end
 
@@ -40,7 +40,7 @@ module ActiveRecord
         #   - options parent is present and database option is not present
         #   - migrations option is nil or false
         def skip_migration_creation?
-          parent && !database || !migration
+          custom_parent? && !database || !migration
         end
 
         def attributes_with_index
@@ -49,12 +49,12 @@ module ActiveRecord
 
         # Used by the migration template to determine the parent name of the model
         def parent_class_name
-          if parent
+          if custom_parent?
             parent
           elsif database
             abstract_class_name
           else
-            "ApplicationRecord"
+            parent
           end
         end
 
@@ -77,6 +77,10 @@ module ActiveRecord
           options[:parent]
         end
 
+        def custom_parent?
+          parent != self.class.class_options[:parent].default
+        end
+
         def migration
           options[:migration]
         end

railties/lib/rails/generators/rails/controller/controller_generator.rb

@@ -6,7 +6,7 @@ module Rails
       argument :actions, type: :array, default: [], banner: "action action"
       class_option :skip_routes, type: :boolean, desc: "Don't add routes to config/routes.rb."
       class_option :helper, type: :boolean
-      class_option :parent, type: :string, desc: "The parent class for the generated controller"
+      class_option :parent, type: :string, default: "ApplicationController", desc: "The parent class for the generated controller"
 
       check_class_collision suffix: "Controller"
 
@@ -26,16 +26,8 @@ module Rails
       end
 
       private
-        def parent
-          options[:parent]
-        end
-
         def parent_class_name
-          if parent
-            parent
-          else
-            "ApplicationController"
-          end
+          options[:parent]
         end
 
         def file_name