define include_XXX? methods, which can be overridden to conditionally include attributes and associations

lib/active_model/serializer.rb

@@ -328,6 +328,8 @@ module ActiveModel
             object.read_attribute_for_serialization(attr.to_sym)
           end
         end
+
+        define_include_method attr
       end
 
       def associate(klass, attrs) #:nodoc:
@@ -341,10 +343,21 @@ module ActiveModel
             end
           end
 
+          define_include_method attr
+
           self._associations[attr] = klass.refine(attr, options)
         end
       end
 
+      def define_include_method(name)
+        method = "include_#{name}?".to_sym
+        unless method_defined?(method)
+          define_method method do
+            true
+          end
+        end
+      end
+
       # Defines an association in the object should be rendered.
       #
       # The serializer object should implement the association name
@@ -486,10 +499,14 @@ module ActiveModel
 
     def include_associations!
       _associations.each_key do |name|
-        include! name
+        include!(name) if include?(name)
       end
     end
 
+    def include?(name)
+      send "include_#{name}?".to_sym
+    end
+
     def include!(name, options={})
       # Make sure that if a special options[:hash] was passed in, we generate
       # a new unique values hash and don't clobber the original. If the hash
@@ -569,7 +586,7 @@ module ActiveModel
       hash = {}
 
       _attributes.each do |name,key|
-        hash[key] = read_attribute_for_serialization(name)
+        hash[key] = read_attribute_for_serialization(name) if include?(name)
       end
 
       hash

test/serializer_test.rb

@@ -227,6 +227,62 @@ class SerializerTest < ActiveModel::TestCase
     }, post_serializer.as_json)
   end
 
+  class PostWithMultipleConditionalsSerializer < ActiveModel::Serializer
+    root :post
+    attributes :title, :body, :author
+    has_many :comments, :serializer => CommentSerializer
+
+    def include_comments?
+      !object.comments_disabled
+    end
+
+    def include_author?
+      scope.super_user?
+    end
+  end
+
+  def test_conditionally_included_associations_and_attributes
+    user = User.new
+
+    post = Post.new(:title => "New Post", :body => "Body of new post", :author => 'Sausage King', :email => "tenderlove@tenderlove.com")
+    comments = [Comment.new(:title => "Comment1"), Comment.new(:title => "Comment2")]
+    post.comments = comments
+
+    post_serializer = PostWithMultipleConditionalsSerializer.new(post, :scope => user)
+
+    # comments enabled
+    post.comments_disabled = false
+    assert_equal({
+      :post => {
+        :title => "New Post",
+        :body => "Body of new post",
+        :comments => [
+          { :title => "Comment1" },
+          { :title => "Comment2" }
+        ]
+      }
+    }, post_serializer.as_json)
+
+    # comments disabled
+    post.comments_disabled = true
+    assert_equal({
+      :post => {
+        :title => "New Post",
+        :body => "Body of new post"
+      }
+    }, post_serializer.as_json)
+
+    # superuser - should see author
+    user.superuser = true
+    assert_equal({
+      :post => {
+        :title => "New Post",
+        :body => "Body of new post",
+        :author => "Sausage King"
+      }
+    }, post_serializer.as_json)
+  end
+
   class Blog < Model
     attr_accessor :author
   end