Serialize fewer pipeline fields for MR widget

Frontend doesn't need all the information currently provided
This commit reduces the number of serialized fields to the
necessary ones

app/assets/javascripts/vue_merge_request_widget/components/mr_widget_pipeline.vue

@@ -84,9 +84,6 @@ export default {
     hasCommitInfo() {
       return this.pipeline.commit && Object.keys(this.pipeline.commit).length > 0;
     },
-    isTriggeredByMergeRequest() {
-      return Boolean(this.pipeline.merge_request);
-    },
     isMergeRequestPipeline() {
       return Boolean(this.pipeline.flags && this.pipeline.flags.merge_request_pipeline);
     },

app/serializers/merge_request_poll_widget_entity.rb

@@ -19,9 +19,21 @@ class MergeRequestPollWidgetEntity < Grape::Entity
   # User entities
   expose :merge_user, using: UserEntity
 
-  expose :actual_head_pipeline, with: PipelineDetailsEntity, as: :pipeline, if: -> (mr, _) { presenter(mr).can_read_pipeline? }
+  expose :actual_head_pipeline, as: :pipeline, if: -> (mr, _) { presenter(mr).can_read_pipeline? } do |merge_request, options|
+    if Feature.enabled?(:merge_request_short_pipeline_serializer, merge_request.project)
+      MergeRequests::PipelineEntity.represent(merge_request.actual_head_pipeline, options)
+    else
+      PipelineDetailsEntity.represent(merge_request.actual_head_pipeline, options)
+    end
+  end
 
-  expose :merge_pipeline, with: PipelineDetailsEntity, if: ->(mr, _) { mr.merged? && can?(request.current_user, :read_pipeline, mr.target_project)}
+  expose :merge_pipeline, if: ->(mr, _) { mr.merged? && can?(request.current_user, :read_pipeline, mr.target_project)} do |merge_request, options|
+    if Feature.enabled?(:merge_request_short_pipeline_serializer, merge_request.project)
+      MergeRequests::PipelineEntity.represent(merge_request.merge_pipeline, options)
+    else
+      PipelineDetailsEntity.represent(merge_request.merge_pipeline, options)
+    end
+  end
 
   expose :default_merge_commit_message
 

app/serializers/merge_requests/pipeline_entity.rb

+# frozen_string_literal: true
+
+class MergeRequests::PipelineEntity < Grape::Entity
+  include RequestAwareEntity
+
+  expose :id
+  expose :active?, as: :active
+
+  expose :path do |pipeline|
+    project_pipeline_path(pipeline.project, pipeline)
+  end
+
+  expose :flags do
+    expose :merge_request_pipeline?, as: :merge_request_pipeline
+  end
+
+  expose :commit, using: CommitEntity
+
+  expose :details do
+    expose :name do |pipeline|
+      pipeline.present.name
+    end
+
+    expose :detailed_status, as: :status, with: DetailedStatusEntity do |pipeline|
+      pipeline.detailed_status(request.current_user)
+    end
+
+    expose :ordered_stages, as: :stages, using: StageEntity
+  end
+
+  # Coverage isn't always necessary (e.g. when displaying project pipelines in
+  # the UI). Instead of creating an entirely different entity we just allow the
+  # disabling of this specific field whenever necessary.
+  expose :coverage, unless: proc { options[:disable_coverage] }
+
+  expose :ref do
+    expose :branch?, as: :branch
+  end
+
+  expose :triggered_by_pipeline, as: :triggered_by, with: TriggeredPipelineEntity
+  expose :triggered_pipelines, as: :triggered, using: TriggeredPipelineEntity
+end

spec/serializers/merge_request_poll_widget_entity_spec.rb

@@ -36,13 +36,28 @@ RSpec.describe MergeRequestPollWidgetEntity do
 
       it 'returns merge_pipeline' do
         pipeline.reload
-        pipeline_payload = PipelineDetailsEntity
-                             .represent(pipeline, request: request)
-                             .as_json
+        pipeline_payload =
+          MergeRequests::PipelineEntity
+            .represent(pipeline, request: request)
+            .as_json
 
         expect(subject[:merge_pipeline]).to eq(pipeline_payload)
       end
 
+      context 'when merge_request_short_pipeline_serializer is disabled' do
+        it 'returns detailed info about pipeline' do
+          stub_feature_flags(merge_request_short_pipeline_serializer: false)
+
+          pipeline.reload
+          pipeline_payload =
+            PipelineDetailsEntity
+              .represent(pipeline, request: request)
+              .as_json
+
+          expect(subject[:merge_pipeline]).to eq(pipeline_payload)
+        end
+      end
+
       context 'when user cannot read pipelines on target project' do
         before do
           project.add_guest(user)
@@ -222,13 +237,27 @@ RSpec.describe MergeRequestPollWidgetEntity do
         let(:req) { double('request', current_user: user, project: project) }
 
         it 'returns pipeline' do
-          pipeline_payload = PipelineDetailsEntity
-            .represent(pipeline, request: req)
-            .as_json
+          pipeline_payload =
+            MergeRequests::PipelineEntity
+              .represent(pipeline, request: req)
+              .as_json
 
           expect(subject[:pipeline]).to eq(pipeline_payload)
         end
 
+        context 'when merge_request_short_pipeline_serializer is disabled' do
+          it 'returns detailed info about pipeline' do
+            stub_feature_flags(merge_request_short_pipeline_serializer: false)
+
+            pipeline_payload =
+              PipelineDetailsEntity
+                .represent(pipeline, request: req)
+                .as_json
+
+            expect(subject[:pipeline]).to eq(pipeline_payload)
+          end
+        end
+
         it 'returns ci_status' do
           expect(subject[:ci_status]).to eq('pending')
         end

spec/serializers/merge_requests/pipeline_entity_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe MergeRequests::PipelineEntity do
+  let_it_be(:project) { create(:project, :repository) }
+  let_it_be(:user) { create(:user) }
+  let_it_be(:pipeline) { create(:ci_pipeline, project: project) }
+
+  let(:request) { double('request') }
+
+  before do
+    stub_not_protect_default_branch
+
+    allow(request).to receive(:current_user).and_return(user)
+    allow(request).to receive(:project).and_return(project)
+  end
+
+  let(:entity) do
+    described_class.represent(pipeline, request: request)
+  end
+
+  subject { entity.as_json }
+
+  describe '#as_json' do
+    it 'contains required fields' do
+      is_expected.to include(
+        :id, :path, :active, :coverage, :ref, :commit, :details,
+        :flags, :triggered, :triggered_by
+      )
+      expect(subject[:commit]).to include(:short_id, :commit_path)
+      expect(subject[:ref]).to include(:branch)
+      expect(subject[:details]).to include(:name, :status, :stages)
+      expect(subject[:details][:status]).to include(:icon, :favicon, :text, :label, :tooltip)
+      expect(subject[:flags]).to include(:merge_request_pipeline)
+    end
+
+    it 'excludes coverage data when disabled' do
+      entity = described_class
+        .represent(pipeline, request: request, disable_coverage: true)
+
+      expect(entity.as_json).not_to include(:coverage)
+    end
+  end
+end

spec/serializers/pipeline_entity_spec.rb

@@ -7,7 +7,6 @@ RSpec.describe PipelineEntity do
 
   let_it_be(:project) { create(:project) }
   let_it_be(:user) { create(:user) }
-  let_it_be(:project) { create(:project) }
   let(:request) { double('request') }
 
   before do