Add ability to specify validation context

In some cases, users want to run API-specific validations. This commit allows
to pass a validation context to the JSONAPI::Resource#_super method

Author: Yevhenii Kurtov

lib/jsonapi/resource.rb

@@ -182,8 +182,8 @@ def save
     #   return :accepted
     # end
     # ```
-    def _save
-      unless @model.valid?
+    def _save(validation_context = nil)
+      unless @model.valid?(validation_context)
         fail JSONAPI::Exceptions::ValidationErrors.new(self)
       end
 

test/fixtures/active_record.rb

@@ -406,7 +406,7 @@ def destroy
     $breed_data.remove(@id)
   end
 
-  def valid?
+  def valid?(context = nil)
     @errors.clear
     if name.is_a?(String) && name.length > 0
       return true

test/unit/resource/resource_test.rb

@@ -18,11 +18,28 @@ def do_some_after_save_stuff
   end
 end
 
+class PostWithCustomValidationContext < ActiveRecord::Base
+  self.table_name = 'posts'
+  validate :api_specific_check, on: :json_api_create
+
+  def api_specific_check
+    errors[:base] << 'Record is invalid'
+  end
+end
+
 class ArticleWithBadAfterSaveResource < JSONAPI::Resource
   model_name 'PostWithBadAfterSave'
   attribute :title
 end
 
+class ArticleWithCustomValidationContextResource < JSONAPI::Resource
+  model_name 'PostWithCustomValidationContext'
+  attribute :title
+  def _save
+    super(:json_api_create)
+  end
+end
+
 class NoMatchResource < JSONAPI::Resource
 end
 
@@ -557,4 +574,13 @@ def test_resource_for_model_use_hint
     resource_model = SpecialPersonResource.records({}).first # simulate a find
     assert_equal(SpecialPersonResource, SpecialPersonResource.resource_for_model(resource_model))
   end
+
+  def test_resource_performs_validations_in_custom_context
+    post = PostWithCustomValidationContext.find(1)
+    post_resource = ArticleWithCustomValidationContextResource.new(post, nil)
+    err = assert_raises JSONAPI::Exceptions::ValidationErrors do
+      post_resource._save
+    end
+    assert_equal(err.error_messages[:base], ['Record is invalid'])
+  end
 end