Add if/unless support to attributes.

Author: beauby

lib/active_model/serializer/attribute.rb

@@ -1,13 +1,38 @@
 module ActiveModel
   class Serializer
-    Attribute = Struct.new(:name, :key, :block) do
+    Attribute = Struct.new(:name, :block, :key, :condition_type, :condition) do
+      def initialize(name, block, options)
+        super(name, block)
+        self.key = options.fetch(:key, name)
+        self.condition_type =
+          if options.key?(:if)
+            :if
+          elsif options.key?(:unless)
+            :unless
+          else
+            :none
+          end
+        self.condition = options[condition_type]
+      end
+
       def value(serializer)
         if block
           serializer.instance_eval(&block)
         else
           serializer.read_attribute_for_serialization(name)
         end
       end
+
+      def include?(serializer)
+        case condition_type
+        when :if
+          serializer.send(condition)
+        when :unless
+          !serializer.send(condition)
+        else
+          true
+        end
+      end
     end
   end
 end

lib/active_model/serializer/attributes.rb

@@ -16,6 +16,7 @@ module Attributes
         def attributes(requested_attrs = nil, reload = false)
           @attributes = nil if reload
           @attributes ||= self.class._attributes_data.values.each_with_object({}) do |attr, hash|
+            next unless attr.include?(self)
             next unless requested_attrs.nil? || requested_attrs.include?(attr.key)
             hash[attr.key] = attr.value(self)
           end
@@ -52,8 +53,7 @@ def attributes(*attrs)
         #       object.edits.last(5)
         #     end
         def attribute(attr, options = {}, &block)
-          key = options.fetch(:key, attr)
-          _attributes_data[attr] = Attribute.new(attr, key, block)
+          _attributes_data[attr] = Attribute.new(attr, block, options)
         end
 
         # @api private