Require `belongs_to` by default.

Deprecate `required` option in favor of `optional` for belongs_to.

5 files changed, 67 insertions, 1 deletions

diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 74d1ca3bd8..df9f8fe993 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,18 @@
+*   Add `config/initializers/active_record_belongs_to_required_by_default.rb`
+
+    Newly generated Rails apps have a new initializer called
+    `active_record_belongs_to_required_by_default.rb` which sets the value of
+    the configuration option `config.active_record.belongs_to_requred_by_default`
+    to `true` when ActiveRecord is not skipped.
+
+    As a result, new Rails apps require `belongs_to` association on model
+    to be valid.
+
+    This initializer is *not* added when running `rake rails:update`, so
+    old apps ported to Rails 5 will work without any change.
+
+    *Josef Šimánek*
+
 *   `delete` operations in configurations are run last in order to eliminate
     'No such middleware' errors when `insert_before` or `insert_after` are added
     after the `delete` operation for the middleware being deleted.
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index 977f5a1c03..899b33e529 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -89,6 +89,7 @@ module Rails
     def config_when_updating
       cookie_serializer_config_exist = File.exist?('config/initializers/cookies_serializer.rb')
       callback_terminator_config_exist = File.exist?('config/initializers/callback_terminator.rb')
+      active_record_belongs_to_required_by_default_config_exist = File.exist?('config/initializers/active_record_belongs_to_required_by_default.rb')
 
       config
 
@@ -99,6 +100,10 @@ module Rails
       unless cookie_serializer_config_exist
         gsub_file 'config/initializers/cookies_serializer.rb', /json/, 'marshal'
       end
+
+      unless active_record_belongs_to_required_by_default_config_exist
+        remove_file 'config/initializers/active_record_belongs_to_required_by_default.rb'
+      end
     end
 
     def database_yml
@@ -258,6 +263,12 @@ module Rails
         end
       end
 
+      def delete_active_record_initializers_skipping_active_record
+        if options[:skip_active_record]
+          remove_file 'config/initializers/active_record_belongs_to_required_by_default.rb'
+        end
+      end
+
       def finish_template
         build(:leftovers)
       end
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/active_record_belongs_to_required_by_default.rb b/railties/lib/rails/generators/rails/app/templates/config/initializers/active_record_belongs_to_required_by_default.rb
new file mode 100644
index 0000000000..30c4f89792
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/active_record_belongs_to_required_by_default.rb
@@ -0,0 +1,4 @@
+# Be sure to restart your server when you modify this file.
+
+# Require `belongs_to` associations by default.
+Rails.application.config.active_record.belongs_to_required_by_default = true
diff --git a/railties/test/application/rake_test.rb b/railties/test/application/rake_test.rb
index 8d71b813e6..2bff21dae5 100644
--- a/railties/test/application/rake_test.rb
+++ b/railties/test/application/rake_test.rb
@@ -194,7 +194,10 @@ module ApplicationTests
       assert_no_match(/Errors running/, output)
     end
 
-    def test_scaffold_with_references_columns_tests_pass_by_default
+    def test_scaffold_with_references_columns_tests_pass_when_belongs_to_is_optional
+      app_file "config/initializers/active_record_belongs_to_required_by_default.rb",
+        "Rails.application.config.active_record.belongs_to_required_by_default = false"
+
       output = Dir.chdir(app_path) do
         `rails generate scaffold LineItems product:references cart:belongs_to;
          bundle exec rake db:migrate test`
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index ca26e0c8d7..4c5dd70a88 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -209,6 +209,38 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_file("#{app_root}/config/initializers/cookies_serializer.rb", /Rails\.application\.config\.action_dispatch\.cookies_serializer = :marshal/)
   end
 
+  def test_rails_update_does_not_create_active_record_belongs_to_required_by_default
+    app_root = File.join(destination_root, 'myapp')
+    run_generator [app_root]
+
+    FileUtils.rm("#{app_root}/config/initializers/active_record_belongs_to_required_by_default.rb")
+
+    Rails.application.config.root = app_root
+    Rails.application.class.stubs(:name).returns("Myapp")
+    Rails.application.stubs(:is_a?).returns(Rails::Application)
+
+    generator = Rails::Generators::AppGenerator.new ["rails"], { with_dispatchers: true }, destination_root: app_root, shell: @shell
+    generator.send(:app_const)
+    quietly { generator.send(:update_config_files) }
+    assert_no_file "#{app_root}/config/initializers/active_record_belongs_to_required_by_default.rb"
+  end
+
+  def test_rails_update_does_not_remove_active_record_belongs_to_required_by_default_if_already_present
+    app_root = File.join(destination_root, 'myapp')
+    run_generator [app_root]
+
+    FileUtils.touch("#{app_root}/config/initializers/active_record_belongs_to_required_by_default.rb")
+
+    Rails.application.config.root = app_root
+    Rails.application.class.stubs(:name).returns("Myapp")
+    Rails.application.stubs(:is_a?).returns(Rails::Application)
+
+    generator = Rails::Generators::AppGenerator.new ["rails"], { with_dispatchers: true }, destination_root: app_root, shell: @shell
+    generator.send(:app_const)
+    quietly { generator.send(:update_config_files) }
+    assert_file "#{app_root}/config/initializers/active_record_belongs_to_required_by_default.rb"
+  end
+
   def test_application_names_are_not_singularized
     run_generator [File.join(destination_root, "hats")]
     assert_file "hats/config/environment.rb", /Rails\.application\.initialize!/
@@ -309,6 +341,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
   def test_generator_if_skip_active_record_is_given
     run_generator [destination_root, "--skip-active-record"]
     assert_no_file "config/database.yml"
+    assert_no_file "config/initializers/active_record_belongs_to_required_by_default.rb"
     assert_file "config/application.rb", /#\s+require\s+["']active_record\/railtie["']/
     assert_file "test/test_helper.rb" do |helper_content|
       assert_no_match(/fixtures :all/, helper_content)