Allow the serializer to return sparse fieldsets

lib/fast_jsonapi/fieldset.rb

@@ -0,0 +1,7 @@
+module FastJsonapi
+  class Fieldset
+    def initialize(fields)
+      @fields = fields
+    end
+  end
+end

lib/fast_jsonapi/object_serializer.rb

@@ -7,6 +7,7 @@ require 'fast_jsonapi/attribute'
 require 'fast_jsonapi/relationship'
 require 'fast_jsonapi/link'
 require 'fast_jsonapi/serialization_core'
+require 'fast_jsonapi/fieldset'
 
 module FastJsonapi
   module ObjectSerializer
@@ -41,8 +42,8 @@ module FastJsonapi
 
       return serializable_hash unless @resource
 
-      serializable_hash[:data] = self.class.record_hash(@resource, @params)
+      serializable_hash[:data] = self.class.record_hash(@resource, @fieldsets[self.class.reflected_record_type.to_sym], @params)
-      serializable_hash[:included] = self.class.get_included_records(@resource, @includes, @known_included_objects, @params) if @includes.present?
+      serializable_hash[:included] = self.class.get_included_records(@resource, @includes, @known_included_objects, @fieldsets, @params) if @includes.present?
       serializable_hash
     end
 
@@ -51,9 +52,10 @@ module FastJsonapi
 
       data = []
       included = []
+      fieldset = @fieldsets[self.class.reflected_record_type.to_sym]
       @resource.each do |record|
-        data << self.class.record_hash(record, @params)
+        data << self.class.record_hash(record, fieldset, @params)
-        included.concat self.class.get_included_records(record, @includes, @known_included_objects, @params) if @includes.present?
+        included.concat self.class.get_included_records(record, @includes, @known_included_objects, @fieldsets, @params) if @includes.present?
       end
 
       serializable_hash[:data] = data
@@ -70,6 +72,8 @@ module FastJsonapi
     private
 
     def process_options(options)
+      @fieldsets = deep_symbolize(options[:fields].presence || {})
+
       return if options.blank?
 
       @known_included_objects = {}
@@ -85,6 +89,18 @@ module FastJsonapi
       end
     end
 
+    def deep_symbolize(collection)
+      if collection.is_a? Hash
+        Hash[collection.map do |k, v|
+          [k.to_sym, deep_symbolize(v)]
+        end]
+      elsif collection.is_a? Array
+        collection.map { |i| deep_symbolize(i) }
+      else
+        collection.to_sym
+      end
+    end
+
     def is_collection?(resource, force_is_collection = nil)
       return force_is_collection unless force_is_collection.nil?
 
@@ -104,6 +120,7 @@ module FastJsonapi
         subclass.race_condition_ttl = race_condition_ttl
         subclass.data_links = data_links
         subclass.cached = cached
+        subclass.fieldset = fieldset.dup if fieldset.present?
       end
 
       def reflected_record_type

lib/fast_jsonapi/serialization_core.rb

@@ -21,7 +21,8 @@ module FastJsonapi
                       :cache_length,
                       :race_condition_ttl,
                       :cached,
-                      :data_links
+                      :data_links,
+                      :fieldset
       end
     end
 
@@ -40,27 +41,30 @@ module FastJsonapi
         end
       end
 
-      def attributes_hash(record, params = {})
+      def attributes_hash(record, fieldset = nil, params = {})
-        attributes_to_serialize.each_with_object({}) do |(_k, attribute), hash|
+        attributes = attributes_to_serialize
+        attributes = attributes.slice(*fieldset) if fieldset.present?
+        attributes.each_with_object({}) do |(_k, attribute), hash|
           attribute.serialize(record, params, hash)
         end
       end
 
-      def relationships_hash(record, relationships = nil, params = {})
+      def relationships_hash(record, relationships = nil, fieldset = nil, params = {})
         relationships = relationships_to_serialize if relationships.nil?
+        relationships = relationships.slice(*fieldset) if fieldset.present?
 
         relationships.each_with_object({}) do |(_k, relationship), hash|
           relationship.serialize(record, params, hash)
         end
       end
 
-      def record_hash(record, params = {})
+      def record_hash(record, fieldset, params = {})
         if cached
           record_hash = Rails.cache.fetch(record.cache_key, expires_in: cache_length, race_condition_ttl: race_condition_ttl) do
             temp_hash = id_hash(id_from_record(record), record_type, true)
-            temp_hash[:attributes] = attributes_hash(record, params) if attributes_to_serialize.present?
+            temp_hash[:attributes] = attributes_hash(record, fieldset, params) if attributes_to_serialize.present?
             temp_hash[:relationships] = {}
-            temp_hash[:relationships] = relationships_hash(record, cachable_relationships_to_serialize, params) if cachable_relationships_to_serialize.present?
+            temp_hash[:relationships] = relationships_hash(record, cachable_relationships_to_serialize, fieldset, params) if cachable_relationships_to_serialize.present?
             temp_hash[:links] = links_hash(record, params) if data_links.present?
             temp_hash
           end
@@ -68,8 +72,8 @@ module FastJsonapi
           record_hash
         else
           record_hash = id_hash(id_from_record(record), record_type, true)
-          record_hash[:attributes] = attributes_hash(record, params) if attributes_to_serialize.present?
+          record_hash[:attributes] = attributes_hash(record, fieldset, params) if attributes_to_serialize.present?
-          record_hash[:relationships] = relationships_hash(record, nil, params) if relationships_to_serialize.present?
+          record_hash[:relationships] = relationships_hash(record, nil, fieldset, params) if relationships_to_serialize.present?
           record_hash[:links] = links_hash(record, params) if data_links.present?
           record_hash
         end
@@ -100,7 +104,7 @@ module FastJsonapi
       end
 
       # includes handler
-      def get_included_records(record, includes_list, known_included_objects, params = {})
+      def get_included_records(record, includes_list, known_included_objects, fieldsets, params = {})
         return unless includes_list.present?
 
         includes_list.sort.each_with_object([]) do |include_item, included_records|
@@ -120,7 +124,7 @@ module FastJsonapi
 
             included_objects.each do |inc_obj|
               if remaining_items(items)
-                serializer_records = serializer.get_included_records(inc_obj, remaining_items(items), known_included_objects)
+                serializer_records = serializer.get_included_records(inc_obj, remaining_items(items), known_included_objects, fieldsets)
                 included_records.concat(serializer_records) unless serializer_records.empty?
               end
 
@@ -128,7 +132,8 @@ module FastJsonapi
               next if known_included_objects.key?(code)
 
               known_included_objects[code] = inc_obj
-              included_records << serializer.record_hash(inc_obj, params)
+
+              included_records << serializer.record_hash(inc_obj, fieldsets[serializer.reflected_record_type], params)
             end
           end
         end

spec/lib/object_serializer_fields_spec.rb

@@ -0,0 +1,36 @@
+require 'spec_helper'
+
+describe FastJsonapi::ObjectSerializer do
+  include_context 'movie class'
+
+  let(:fields) do
+    {
+      movie: %i[name actors],
+      actor: %i[name agency]
+    }
+  end
+
+  it 'only returns specified fields' do
+    hash = MovieSerializer.new(movie, fields: fields).serializable_hash
+
+    expect(hash[:data][:attributes].keys.sort).to eq %i[name]
+  end
+
+  it 'only returns specified relationships' do
+    hash = MovieSerializer.new(movie, fields: fields).serializable_hash
+
+    expect(hash[:data][:relationships].keys.sort).to eq %i[actors]
+  end
+
+  it 'only returns specified fields for included relationships' do
+    hash = MovieSerializer.new(movie, fields: fields, include: %i[actors]).serializable_hash
+
+    expect(hash[:included].first[:attributes].keys.sort).to eq %i[name]
+  end
+
+  it 'only returns specified relationships for included relationships' do
+    hash = MovieSerializer.new(movie, fields: fields, include: %i[actors]).serializable_hash
+
+    expect(hash[:included].first[:relationships].keys.sort).to eq %i[agency]
+  end
+end

spec/lib/serialization_core_spec.rb

@@ -64,7 +64,7 @@ describe FastJsonapi::ObjectSerializer do
       known_included_objects = {}
       included_records = []
       [movie, movie].each do |record|
-        included_records.concat MovieSerializer.send(:get_included_records, record, includes_list, known_included_objects, nil)
+        included_records.concat MovieSerializer.send(:get_included_records, record, includes_list, known_included_objects, {}, nil)
       end
       expect(included_records.size).to eq 3
     end