Allow conditional attributes

lib/fast_jsonapi/object_serializer.rb

@@ -149,13 +149,20 @@ module FastJsonapi
 
       def attributes(*attributes_list, &block)
         attributes_list = attributes_list.first if attributes_list.first.class.is_a?(Array)
+        options = attributes_list.last.is_a?(Hash) ? attributes_list.pop : {}
         self.attributes_to_serialize = {} if self.attributes_to_serialize.nil?
+        self.optional_attributes_to_serialize = {} if self.optional_attributes_to_serialize.nil?
+
         attributes_list.each do |attr_name|
           method_name = attr_name
           key = run_key_transform(method_name)
+          if options[:if].present?
+            optional_attributes_to_serialize[key] = [method_name, options[:if]]
+          else
             attributes_to_serialize[key] = block || method_name
           end
         end
+      end
 
       alias_method :attribute, :attributes
 

lib/fast_jsonapi/serialization_core.rb

@@ -12,6 +12,7 @@ module FastJsonapi
     included do
       class << self
         attr_accessor :attributes_to_serialize,
+                      :optional_attributes_to_serialize,
                       :relationships_to_serialize,
                       :cachable_relationships_to_serialize,
                       :uncachable_relationships_to_serialize,
@@ -73,13 +74,21 @@ module FastJsonapi
       end
 
       def attributes_hash(record, params = {})
-        attributes_to_serialize.each_with_object({}) do |(key, method), attr_hash|
+        attributes = attributes_to_serialize.each_with_object({}) do |(key, method), attr_hash|
           attr_hash[key] = if method.is_a?(Proc)
             method.arity == 1 ? method.call(record) : method.call(record, params)
           else
             record.public_send(method)
           end
         end
+
+        self.optional_attributes_to_serialize = {} if self.optional_attributes_to_serialize.nil?
+        optional_attributes_to_serialize.each do |key, details|
+          method_name, check_proc = details
+          attributes[key] = record.send(method_name) if check_proc.call(record, params)
+        end
+
+        attributes
       end
 
       def relationships_hash(record, relationships = nil, params = {})

spec/lib/object_serializer_spec.rb

@@ -309,4 +309,36 @@ describe FastJsonapi::ObjectSerializer do
       expect(serializable_hash[:included][0][:links][:self]).to eq url
     end
   end
+
+  context 'when optional attributes are determined by record data' do
+    it 'returns optional attribute when attribute is included' do
+      movie.release_year = 2001
+      json = MovieOptionalRecordDataSerializer.new(movie).serialized_json
+      serializable_hash = JSON.parse(json)
+      expect(serializable_hash['data']['attributes']['release_year']).to eq movie.release_year
+    end
+
+    it "doesn't return optional attribute when attribute is not included" do
+      movie.release_year = 1970
+      json = MovieOptionalRecordDataSerializer.new(movie).serialized_json
+      serializable_hash = JSON.parse(json)
+      expect(serializable_hash['data']['attributes'].has_key?('release_year')).to be_falsey
+    end
+  end
+
+  context 'when optional attributes are determined by params data' do
+    it 'returns optional attribute when attribute is included' do
+      movie.director = 'steven spielberg'
+      json = MovieOptionalParamsDataSerializer.new(movie, { params: { admin: true }}).serialized_json
+      serializable_hash = JSON.parse(json)
+      expect(serializable_hash['data']['attributes']['director']).to eq 'steven spielberg'
+    end
+
+    it "doesn't return optional attribute when attribute is not included" do
+      movie.director = 'steven spielberg'
+      json = MovieOptionalParamsDataSerializer.new(movie, { params: { admin: false }}).serialized_json
+      serializable_hash = JSON.parse(json)
+      expect(serializable_hash['data']['attributes'].has_key?('director')).to be_falsey
+    end
+  end
 end

spec/shared/contexts/movie_context.rb

@@ -278,6 +278,20 @@ RSpec.shared_context 'movie class' do
       set_type :account
       belongs_to :supplier
     end
+
+    class MovieOptionalRecordDataSerializer
+      include FastJsonapi::ObjectSerializer
+      set_type :movie
+      attributes :name
+      attribute :release_year, if: Proc.new { |record| record.release_year >= 2000 }
+    end
+
+    class MovieOptionalParamsDataSerializer
+      include FastJsonapi::ObjectSerializer
+      set_type :movie
+      attributes :name
+      attribute :director, if: Proc.new { |record, params| params && params[:admin] == true }
+    end
   end