1 files changed, 11 insertions, 6 deletions
diff --git a/activerecord/lib/active_record/associations/builder/has_one.rb b/activerecord/lib/active_record/associations/builder/has_one.rb
index c194c8ae9a..9d64ae877b 100644
--- a/activerecord/lib/active_record/associations/builder/has_one.rb
+++ b/activerecord/lib/active_record/associations/builder/has_one.rb
@@ -1,11 +1,11 @@
-module ActiveRecord::Associations::Builder
+module ActiveRecord::Associations::Builder # :nodoc:
   class HasOne < SingularAssociation #:nodoc:
-    def macro
+    def self.macro
       :has_one
     end
 
-    def valid_options
-      valid = super + [:as]
+    def self.valid_options(options)
+      valid = super + [:as, :foreign_type]
       valid += [:through, :source, :source_type] if options[:through]
       valid
     end
@@ -14,10 +14,15 @@ module ActiveRecord::Associations::Builder
       [:destroy, :delete, :nullify, :restrict_with_error, :restrict_with_exception]
     end
 
-    private
-
     def self.add_destroy_callbacks(model, reflection)
       super unless reflection.options[:through]
     end
+
+    def self.define_validations(model, reflection)
+      super
+      if reflection.options[:required]
+        model.validates_presence_of reflection.name, message: :required
+      end
+    end
   end
 end