Merge pull request #50 from felixbuenemann/add-support-for-single-rec…

…ord-serialization

Add support for single record serialization

lib/postgres_ext/serializers.rb

@@ -10,3 +10,4 @@ module Serializers
 require 'active_model_serializers'
 
 ActiveModel::ArraySerializer.send :prepend, PostgresExt::Serializers::ActiveModel::ArraySerializer
+ActiveModel::Serializer.send :prepend, PostgresExt::Serializers::ActiveModel::Serializer

lib/postgres_ext/serializers/active_model.rb

@@ -4,3 +4,4 @@ module ActiveModel
 end
 
 require 'postgres_ext/serializers/active_model/array_serializer'
+require 'postgres_ext/serializers/active_model/serializer'

lib/postgres_ext/serializers/active_model/array_serializer.rb

@@ -29,7 +29,7 @@ def _postgres_serializable_array
       _reset_internal_state!
       _include_relation_in_root(object, serializer: @options[:each_serializer], root: @options[:root])
 
-      jsons_select_manager = _results_table_arel
+      jsons_select_manager = _results_table_arel(@options[:single_record] ? @options[:root] : nil)
       jsons_select_manager.with @_ctes
 
       @_connection.select_value _to_sql(jsons_select_manager)
@@ -202,7 +202,7 @@ def _coalesce_arrays(column, aliaz = nil)
       _postgres_function_node 'COALESCE', [column, Arel.sql("'{}'")], aliaz
     end
 
-    def _results_table_arel
+    def _results_table_arel(singular_key = nil)
       tables = []
       @_results_tables.each do |key, array|
         json_table = array
@@ -211,9 +211,14 @@ def _results_table_arel
         json_table = Arel::Nodes::As.new json_table, Arel.sql("tbl")
         json_table = Arel::Table.new(:t).from(json_table)
 
-        json_select_manager = @_connection.send('postgresql_version') >= 90300 ?
-          json_table.project("COALESCE(json_agg(tbl), '[]') as #{key}, 1 as match") :
+        json_select_manager = if singular_key.to_s == key.to_s
+          # Single resource is embedded as object instead of array.
+          json_table.project("COALESCE(row_to_json(tbl), '{}') as #{key}, 1 as match")
+        elsif @_connection.send('postgresql_version') >= 90300
+          json_table.project("COALESCE(json_agg(tbl), '[]') as #{key}, 1 as match")
+        else
           json_table.project("COALESCE(array_to_json(array_agg(row_to_json(tbl))), '[]') as #{key}, 1 as match")
+        end
 
         @_ctes << _postgres_cte_as("#{key}_as_json_array", _to_sql(json_select_manager))
         tables << { table: "#{key}_as_json_array", column: key }

lib/postgres_ext/serializers/active_model/serializer.rb

@@ -0,0 +1,38 @@
+module PostgresExt::Serializers::ActiveModel
+  module Serializer
+    def self.prepended(base)
+      class << base
+        prepend ClassMethods
+      end
+    end
+
+    module ClassMethods
+      # Wrap ActiveModel::Serializer.build_json
+      # to send single records through ArraySerializer
+      # enabling database serialization.
+      def build_json(controller, resource, options)
+        serializer_instance = super
+        return serializer_instance unless serializer_instance
+
+        default_options = controller.send(:default_serializer_options) || {}
+        options = default_options.merge(options || {})
+
+        if ActiveRecord::Base === resource && options[:root] != false && serializer_instance.root_name != false
+          options[:root] ||= serializer_instance.root_name
+          options[:each_serializer] = serializer_instance.class
+          options[:single_record] = options.fetch(:single_record, true)
+          options.delete(:serializer) # Reset to default ArraySerializer.
+
+          # Wrap Record in a Relation.
+          klass = resource.class
+          primary_key = klass.primary_key
+          resource = klass.where(primary_key => resource.send(primary_key)).limit(1)
+
+          super(controller, resource, options)
+        else
+          serializer_instance
+        end
+      end
+    end
+  end
+end

test/serializer_test.rb

@@ -1,8 +1,8 @@
 require 'test_helper'
 
-
 describe 'ArraySerializer patch' do
-  let(:json_data)  { ActiveModel::Serializer.build_json(controller, relation, options).to_json }
+  let(:serializer) { ActiveModel::Serializer.build_json(controller, relation, options) }
+  let(:json_data)  { serializer.to_json }
 
   context 'specify serializer' do
     let(:relation)   { Note.all }
@@ -70,4 +70,60 @@
       json_data.must_equal json_expected
     end
   end
+
+  context 'serialize singular record' do
+    let(:relation)   { Note.where(name: 'Title').first }
+    let(:controller) { NotesController.new }
+    let(:options)    { }
+
+    before do
+      @note = Note.create content: 'Test', name: 'Title'
+      @tag = Tag.create name: 'My tag', note: @note, popular: true
+    end
+
+    it 'uses the array serializer' do
+      serializer.must_be_instance_of ActiveModel::ArraySerializer
+    end
+
+    it 'generates the proper json output' do
+      json_expected = %{{"note":{"id":#{@note.id},"content":"Test","name":"Title","tag_ids":[#{@tag.id}]},"tags":[{"id":#{@tag.id},"name":"My tag","note_id":#{@note.id}}]}}
+      json_data.must_equal json_expected
+    end
+  end
+
+  context 'serialize single record with custom serializer' do
+    let(:relation)   { Note.where(name: 'Title').first }
+    let(:controller) { NotesController.new }
+    let(:options)    { { serializer: OtherNoteSerializer } }
+
+    before do
+      @note = Note.create content: 'Test', name: 'Title'
+      @tag = Tag.create name: 'My tag', note: @note
+    end
+
+    it 'uses the array serializer' do
+      serializer.must_be_instance_of ActiveModel::ArraySerializer
+    end
+
+    it 'generates the proper json output' do
+      json_expected = %{{"other_note":{"id":#{@note.id},"name":"Title","tag_ids":[#{@tag.id}]},"tags":[{"id":#{@tag.id},"name":"My tag"}]}}
+      json_data.must_equal json_expected
+    end
+  end
+
+  context 'force single record mode' do
+    let(:relation)   { Note.where(name: 'Title').limit(1) }
+    let(:controller) { NotesController.new }
+    let(:options)    { { root: 'note', single_record: true } }
+
+    before do
+      @note = Note.create content: 'Test', name: 'Title'
+      @tag = Tag.create name: 'My tag', note: @note, popular: true
+    end
+
+    it 'generates the proper json output' do
+      json_expected = %{{"note":{"id":#{@note.id},"content":"Test","name":"Title","tag_ids":[#{@tag.id}]},"tags":[{"id":#{@tag.id},"name":"My tag","note_id":#{@note.id}}]}}
+      json_data.must_equal json_expected
+    end
+  end
 end

test/sideloading_test.rb

@@ -1,3 +1,4 @@
+require 'test_helper'
 
 describe 'ArraySerializer patch' do
   let(:json_data)  { ActiveModel::Serializer.build_json(controller, relation, options).to_json }