Allow save to return false and translates to an error

Allows an ActiveRecord callback to cancel save. This will result in a
`SaveFailed` error.

Author: lgebhardt

lib/jsonapi/error_codes.rb

@@ -19,6 +19,7 @@ module JSONAPI
   INVALID_PAGE_VALUE = 118
   INVALID_FIELD_FORMAT = 119
   INVALID_FILTERS_SYNTAX = 120
+  SAVE_FAILED = 121
   FORBIDDEN = 403
   RECORD_NOT_FOUND = 404
   UNSUPPORTED_MEDIA_TYPE = 415
@@ -44,9 +45,11 @@ module JSONAPI
       INVALID_PAGE_OBJECT => 'INVALID_PAGE_OBJECT',
       INVALID_PAGE_VALUE => 'INVALID_PAGE_VALUE',
       INVALID_FIELD_FORMAT => 'INVALID_FIELD_FORMAT',
+      INVALID_FILTERS_SYNTAX => 'INVALID_FILTERS_SYNTAX',
+      SAVE_FAILED => 'SAVE_FAILED',
       FORBIDDEN => 'FORBIDDEN',
       RECORD_NOT_FOUND => 'RECORD_NOT_FOUND',
       UNSUPPORTED_MEDIA_TYPE => 'UNSUPPORTED_MEDIA_TYPE',
-      LOCKED => 'LOCKED',
-      INVALID_FILTERS_SYNTAX => 'INVALID_FILTERS_SYNTAX' }
+      LOCKED => 'LOCKED'
+    }
 end

lib/jsonapi/exceptions.rb

@@ -305,6 +305,15 @@ def errors
       end
     end
 
+    class SaveFailed < Error
+      def errors
+        [JSONAPI::Error.new(code: JSONAPI::SAVE_FAILED,
+                            status: :unprocessable_entity,
+                            title: 'Save failed or was cancelled',
+                            detail: 'Save failed or was cancelled')]
+      end
+    end
+
     class InvalidPageObject < Error
       def errors
         [JSONAPI::Error.new(code: JSONAPI::INVALID_PAGE_OBJECT,

lib/jsonapi/resource.rb

@@ -124,6 +124,9 @@ def _save
 
       if defined? @model.save
         saved = @model.save
+        unless saved
+          raise JSONAPI::Exceptions::SaveFailed.new
+        end
       else
         saved = true
       end

test/controllers/controller_test.rb

@@ -2322,3 +2322,40 @@ def test_index_default_filter_override
     assert_equal 4, json_response['data'].size
   end
 end
+
+class Api::V1::PlanetsControllerTest < ActionController::TestCase
+  def test_save_model_callbacks
+    set_content_type_header!
+    post :create,
+         {
+           data: {
+             type: 'planets',
+             attributes: {
+               name: 'Zeus',
+               description: 'The largest planet in the solar system. Discovered in 2015.'
+             }
+           }
+         }
+
+    assert_response :created
+    assert json_response['data'].is_a?(Hash)
+    assert_equal 'Zeus', json_response['data']['attributes']['name']
+  end
+
+  def test_save_model_callbacks_fail
+    set_content_type_header!
+    post :create,
+         {
+           data: {
+             type: 'planets',
+             attributes: {
+               name: 'Pluto',
+               description: 'Yes, it is a planet.'
+             }
+           }
+         }
+
+    assert_response :unprocessable_entity
+    assert_match /Save failed or was cancelled/, json_response['errors'][0]['detail']
+  end
+end

test/fixtures/active_record.rb

@@ -222,6 +222,16 @@ class Planet < ActiveRecord::Base
   belongs_to :planet_type
 
   has_and_belongs_to_many :tags, join_table: :planets_tags
+
+  # Test model callback cancelling save
+  before_save :check_not_pluto
+
+  def check_not_pluto
+    # Pluto can't be a planet, so cancel the save
+    if name.downcase == 'pluto'
+      return false
+    end
+  end
 end
 
 class PlanetType < ActiveRecord::Base
@@ -969,7 +979,7 @@ class BadlyNamedAttributesResource < JSONAPI::Resource
                        description: 'Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter.',
                        planet_type_id: planetoid.id)
 titan = Moon.create(name:'Titan', description: 'Best known of the Saturn moons.', planet_id: saturn.id)
-pluto = Planet.create(name: 'Pluto', description: 'Pluto is the smallest planet.', planet_type_id: planetoid.id)
+makemake = Planet.create(name: 'Makemake', description: 'A small planetoid in the Kuiperbelt.', planet_type_id: planetoid.id)
 uranus = Planet.create(name: 'Uranus', description: 'Insert adolescent jokes here.', planet_type_id: gas_giant.id)
 jupiter = Planet.create(name: 'Jupiter', description: 'A gas giant.', planet_type_id: gas_giant.id)
 betax = Planet.create(name: 'Beta X', description: 'Newly discovered Planet X', planet_type_id: unknown.id)

test/unit/operation/operations_processor_test.rb

@@ -304,8 +304,8 @@ def test_remove_resource
     op = JSONAPI::OperationsProcessor.new
 
     count = Planet.count
-    pluto = Planet.find(2)
-    assert_equal(pluto.name, 'Pluto')
+    makemake = Planet.find(2)
+    assert_equal(makemake.name, 'Makemake')
 
     operations = [
       JSONAPI::RemoveResourceOperation.new(PlanetResource, resource_id: 2),