Merge branch 'bvl-patch-mr-serializer' into 'master'

Fall back to the `MergeRequestWidgetEntity`

Closes #41296

See merge request gitlab-org/gitlab-ce!16074

3 files changed, 11 insertions, 3 deletions

diff --git a/app/serializers/merge_request_serializer.rb b/app/serializers/merge_request_serializer.rb
index 52eb30d688a..caf193bdae3 100644
--- a/app/serializers/merge_request_serializer.rb
+++ b/app/serializers/merge_request_serializer.rb
@@ -7,7 +7,7 @@ class MergeRequestSerializer < BaseSerializer
       case opts[:serializer]
       when 'basic', 'sidebar'
         MergeRequestBasicEntity
-      when 'widget'
+      else # It's 'widget'
         MergeRequestWidgetEntity
       end
 
diff --git a/spec/controllers/projects/merge_requests_controller_spec.rb b/spec/controllers/projects/merge_requests_controller_spec.rb
index 58116e6e0fe..45c424af8c4 100644
--- a/spec/controllers/projects/merge_requests_controller_spec.rb
+++ b/spec/controllers/projects/merge_requests_controller_spec.rb
@@ -98,6 +98,14 @@ describe Projects::MergeRequestsController do
           expect(response).to match_response_schema('entities/merge_request_widget')
         end
       end
+
+      context 'when no serialiser was passed' do
+        it 'renders widget MR entity as json' do
+          go(serializer: nil, format: :json)
+
+          expect(response).to match_response_schema('entities/merge_request_widget')
+        end
+      end
     end
 
     describe "as diff" do
diff --git a/spec/serializers/merge_request_serializer_spec.rb b/spec/serializers/merge_request_serializer_spec.rb
index 1ad974c774b..b259cb92962 100644
--- a/spec/serializers/merge_request_serializer_spec.rb
+++ b/spec/serializers/merge_request_serializer_spec.rb
@@ -36,8 +36,8 @@ describe MergeRequestSerializer do
   context 'no serializer' do
     let(:serializer) { nil }
 
-    it 'raises an error' do
-      expect { json_entity }.to raise_error(NoMethodError)
+    it 'falls back to the widget entity' do
+      expect(json_entity).to match_schema('entities/merge_request_widget')
     end
   end
 end