Moves widget Gitaly call from page load to an async request

This moves a Gitaly request from on page load to be inside
of the already loading async request.

app/serializers/merge_request_poll_cached_widget_entity.rb

@@ -104,6 +104,16 @@ class MergeRequestPollCachedWidgetEntity < IssuableEntity
     presenter(merge_request).api_unapprove_path
   end
 
+  expose :blob_path do
+    expose :head_path, if: -> (mr, _) { mr.source_branch_sha } do |merge_request|
+      project_blob_path(merge_request.project, merge_request.source_branch_sha)
+    end
+
+    expose :base_path, if: -> (mr, _) { mr.diff_base_sha } do |merge_request|
+      project_blob_path(merge_request.project, merge_request.diff_base_sha)
+    end
+  end
+
   private
 
   delegate :current_user, to: :request

app/serializers/merge_request_widget_entity.rb

@@ -115,16 +115,6 @@ class MergeRequestWidgetEntity < Grape::Entity
     end
   end
 
-  expose :blob_path do
-    expose :head_path, if: -> (mr, _) { mr.source_branch_sha } do |merge_request|
-      project_blob_path(merge_request.project, merge_request.source_branch_sha)
-    end
-
-    expose :base_path, if: -> (mr, _) { mr.diff_base_sha } do |merge_request|
-      project_blob_path(merge_request.project, merge_request.diff_base_sha)
-    end
-  end
-
   expose :codeclimate, if: -> (mr, _) { head_pipeline_downloadable_path_for_report_type(:codequality) } do
     expose :head_path do |merge_request|
       head_pipeline_downloadable_path_for_report_type(:codequality)

spec/serializers/merge_request_poll_cached_widget_entity_spec.rb

@@ -8,6 +8,7 @@ RSpec.describe MergeRequestPollCachedWidgetEntity do
   let_it_be(:project, refind: true)  { create :project, :repository }
   let_it_be(:resource, refind: true) { create(:merge_request, source_project: project, target_project: project) }
   let_it_be(:user)     { create(:user) }
+  let(:pipeline) { create(:ci_empty_pipeline, project: project) }
 
   let(:request) { double('request', current_user: user, project: project) }
 
@@ -25,6 +26,17 @@ RSpec.describe MergeRequestPollCachedWidgetEntity do
     expect(subject[:merge_status]).to eq 'checking'
   end
 
+  it 'has blob path data' do
+    allow(resource).to receive_messages(
+      base_pipeline: pipeline,
+      head_pipeline: pipeline
+    )
+
+    expect(subject).to include(:blob_path)
+    expect(subject[:blob_path]).to include(:base_path)
+    expect(subject[:blob_path]).to include(:head_path)
+  end
+
   describe 'diverged_commits_count' do
     context 'when MR open and its diverging' do
       it 'returns diverged commits count' do

spec/serializers/merge_request_widget_entity_spec.rb

@@ -76,17 +76,6 @@ RSpec.describe MergeRequestWidgetEntity do
       .to eq("/#{resource.project.full_path}/-/merge_requests/#{resource.iid}.diff")
   end
 
-  it 'has blob path data' do
-    allow(resource).to receive_messages(
-      base_pipeline: pipeline,
-      head_pipeline: pipeline
-    )
-
-    expect(subject).to include(:blob_path)
-    expect(subject[:blob_path]).to include(:base_path)
-    expect(subject[:blob_path]).to include(:head_path)
-  end
-
   describe 'codequality report artifacts', :request_store do
     let(:merge_base_pipeline) { create(:ci_pipeline, :with_codequality_report, project: project) }