Fix resource serialization involving last_result_set

Author: stokarenko

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- [#351](https://github.com/JsonApiClient/json_api_client/pull/351) - Remove rudimental `last_result_set` relationship from serializer
+
 ## 1.12.2
 
 - [#350](https://github.com/JsonApiClient/json_api_client/pull/350) - fix resource including with blank `relationships` response data

lib/json_api_client/resource.rb

@@ -458,7 +458,6 @@ def save
           self.attributes = updated.attributes
           self.links.attributes = updated.links.attributes
           self.relationships.attributes = updated.relationships.attributes
-          self.relationships.last_result_set = last_result_set
           clear_changes_information
           self.relationships.clear_changes_information
           _clear_cached_relationships
@@ -477,7 +476,6 @@ def destroy
         false
       else
         mark_as_destroyed!
-        self.relationships.last_result_set = nil
         _clear_cached_relationships
         _clear_belongs_to_params
         true

test/unit/serializing_test.rb

@@ -52,6 +52,29 @@ def test_as_json
     assert_equal expected, resource.first.as_json
   end
 
+  def test_as_json_involving_last_result_set
+    expected = {
+      'type' => 'articles',
+      'id' => '1',
+      'attributes' => {
+        'title' => 'Rails is Omakase'
+      }
+    }
+    stub_request(:post, "http://example.com/articles")
+      .to_return(headers: {content_type: "application/vnd.api+json"}, body: {
+        data: [{
+          type: "articles",
+          id: "1",
+          attributes: {
+            title: "Rails is Omakase"
+          }
+        }]
+      }.to_json)
+
+    resource = Article.create
+    assert_equal expected, resource.as_json
+  end
+
   def test_as_json_api
     expected = {
       'type' => 'articles',