Return builds with coverage in MR widget JSON

Adds `builds_with_coverage` in the MR widget serializer to be used by
the frontend. These are builds in the head pipeline with
coverage values.

app/models/ci/pipeline.rb

@@ -860,6 +860,10 @@ module Ci
       builds.latest.with_reports(reports_scope)
     end
 
+    def builds_with_coverage
+      builds.with_coverage
+    end
+
     def has_reports?(reports_scope)
       complete? && latest_report_builds(reports_scope).exists?
     end

app/models/merge_request.rb

@@ -295,6 +295,7 @@ class MergeRequest < ApplicationRecord
   alias_attribute :auto_merge_enabled, :merge_when_pipeline_succeeds
   alias_method :issuing_parent, :target_project
 
+  delegate :builds_with_coverage, to: :head_pipeline, allow_nil: true
   delegate :active?, to: :head_pipeline, prefix: true, allow_nil: true
   delegate :success?, :active?, to: :actual_head_pipeline, prefix: true, allow_nil: true
 

app/serializers/build_coverage_entity.rb

+# frozen_string_literal: true
+
+class BuildCoverageEntity < Grape::Entity
+  expose :name, :coverage
+end

app/serializers/merge_request_poll_widget_entity.rb

@@ -73,6 +73,8 @@ class MergeRequestPollWidgetEntity < Grape::Entity
     presenter(merge_request).pipeline_coverage_delta
   end
 
+  expose :builds_with_coverage, using: BuildCoverageEntity
+
   expose :cancel_auto_merge_path do |merge_request|
     presenter(merge_request).cancel_auto_merge_path
   end

changelogs/unreleased/eb-mr-widget-builds-coverages.yml

+---
+title: Return builds with coverage in MR widget JSON response
+merge_request: 40533
+author:
+type: added

spec/controllers/projects/merge_requests/content_controller_spec.rb

@@ -49,6 +49,7 @@ RSpec.describe Projects::MergeRequests::ContentController do
 
         do_request(:widget)
 
+        expect(response).to match_response_schema('entities/merge_request_poll_widget')
         expect(response.headers['Poll-Interval']).to eq('10000')
       end
 
@@ -64,6 +65,20 @@ RSpec.describe Projects::MergeRequests::ContentController do
           expect(response.headers['Poll-Interval']).to eq('300000')
         end
       end
+
+      context 'with coverage data' do
+        let(:merge_request) { create(:merge_request, target_project: project, source_project: project, head_pipeline: head_pipeline) }
+        let!(:base_pipeline) { create(:ci_empty_pipeline, project: project, ref: merge_request.target_branch, sha: merge_request.diff_base_sha) }
+        let!(:head_pipeline) { create(:ci_empty_pipeline, project: project) }
+        let!(:rspec_base) { create(:ci_build, name: 'rspec', coverage: 93.1, pipeline: base_pipeline) }
+        let!(:rspec_head) { create(:ci_build, name: 'rspec', coverage: 97.1, pipeline: head_pipeline) }
+
+        it 'renders widget MR entity as json' do
+          do_request(:widget)
+
+          expect(response).to match_response_schema('entities/merge_request_poll_widget')
+        end
+      end
     end
   end
 

spec/fixtures/api/schemas/entities/merge_request_poll_widget.json

@@ -22,6 +22,14 @@
     "only_allow_merge_if_pipeline_succeeds": { "type": "boolean" },
     "has_ci": { "type": "boolean" },
     "ci_status": { "type": ["string", "null"] },
+    "pipeline_coverage_delta": { "type": ["float", "null"] },
+    "builds_with_coverage": {
+      "type": ["array", "null"],
+      "items": {
+        "type": "object",
+        "required": ["name", "coverage"]
+      }
+    },
     "cancel_auto_merge_path": { "type": ["string", "null"] },
     "test_reports_path": { "type": ["string", "null"] },
     "create_issue_to_resolve_discussions_path": { "type": ["string", "null"] },

spec/models/merge_request_spec.rb

@@ -4112,4 +4112,28 @@ RSpec.describe MergeRequest, factory_default: :keep do
       expect(context[:label_url_method]).to eq(:project_merge_requests_url)
     end
   end
+
+  describe '#builds_with_coverage' do
+    let(:builds) { subject.builds_with_coverage }
+    let(:head_pipeline) { create(:ci_empty_pipeline) }
+    let!(:rspec) { create(:ci_build, name: 'rspec', coverage: 97.1, pipeline: head_pipeline) }
+    let!(:jest) { create(:ci_build, name: 'jest', coverage: 94.1, pipeline: head_pipeline) }
+    let!(:karma) { create(:ci_build, name: 'karma', coverage: nil, pipeline: head_pipeline) }
+
+    context 'when head_pipeline is not present' do
+      it 'returns nil' do
+        expect(builds).to be_nil
+      end
+    end
+
+    context 'when head_pipeline is present' do
+      before do
+        subject.update_attribute(:head_pipeline_id, head_pipeline.id)
+      end
+
+      it 'returns the builds with coverage' do
+        expect(builds).to match_array([rspec, jest])
+      end
+    end
+  end
 end

spec/serializers/merge_request_poll_widget_entity_spec.rb

@@ -285,4 +285,25 @@ RSpec.describe MergeRequestPollWidgetEntity do
       end
     end
   end
+
+  describe '#builds_with_coverage' do
+    let(:result) { subject[:builds_with_coverage] }
+    let(:builds) do
+      [
+        double(name: 'rspec', coverage: 91.5),
+        double(name: 'jest', coverage: 94.1)
+      ]
+    end
+
+    before do
+      allow(resource).to receive(:builds_with_coverage).and_return(builds)
+    end
+
+    it 'serializes the builds with coverage' do
+      expect(result).to eq([
+        { name: 'rspec', coverage: 91.5 },
+        { name: 'jest', coverage: 94.1 }
+      ])
+    end
+  end
 end