Enable suggest pipeline use of experiment helper

- before we didn't get the same level of checks in the
  grape api area.
- by checking the enabling at the helper level we
  can still honor all the frontend items like dnt and such.

app/helpers/issuables_helper.rb

@@ -82,6 +82,7 @@ module IssuablesHelper
                        when Issue
                          IssueSerializer
                        when MergeRequest
+                         opts[:experiment_enabled] = :suggest_pipeline if experiment_enabled?(:suggest_pipeline) && opts[:serializer] == 'widget'
                          MergeRequestSerializer
                        end
 

app/serializers/merge_request_widget_entity.rb

@@ -67,15 +67,15 @@ class MergeRequestWidgetEntity < Grape::Entity
     )
   end
 
-  expose :user_callouts_path, if: -> (*) { Gitlab::Experimentation.enabled?(:suggest_pipeline) } do |_merge_request|
+  expose :user_callouts_path, if: -> (_, opts) { opts[:experiment_enabled] == :suggest_pipeline } do |_merge_request|
     user_callouts_path
   end
 
-  expose :suggest_pipeline_feature_id, if: -> (*) { Gitlab::Experimentation.enabled?(:suggest_pipeline) } do |_merge_request|
+  expose :suggest_pipeline_feature_id, if: -> (_, opts) { opts[:experiment_enabled] == :suggest_pipeline } do |_merge_request|
     SUGGEST_PIPELINE
   end
 
-  expose :is_dismissed_suggest_pipeline, if: -> (*) { Gitlab::Experimentation.enabled?(:suggest_pipeline) } do |_merge_request|
+  expose :is_dismissed_suggest_pipeline, if: -> (_, opts) { opts[:experiment_enabled] == :suggest_pipeline } do |_merge_request|
     current_user && current_user.dismissed_callout?(feature_name: SUGGEST_PIPELINE)
   end
 

spec/helpers/issuables_helper_spec.rb

@@ -369,4 +369,35 @@ RSpec.describe IssuablesHelper do
       expect(helper.sidebar_milestone_tooltip_label(milestone)).to eq('&lt;img onerror=alert(1)&gt;<br/>Milestone')
     end
   end
+
+  describe '#serialize_issuable' do
+    context 'when it is a merge request' do
+      let(:merge_request) { build(:merge_request) }
+      let(:user) { build(:user) }
+
+      before do
+        allow(helper).to receive(:current_user) { user }
+      end
+
+      it 'has suggest_pipeline experiment enabled' do
+        allow(helper).to receive(:experiment_enabled?).with(:suggest_pipeline) { true }
+
+        expect_next_instance_of(MergeRequestSerializer) do |serializer|
+          expect(serializer).to receive(:represent).with(merge_request, { serializer: 'widget', experiment_enabled: :suggest_pipeline })
+        end
+
+        helper.serialize_issuable(merge_request, serializer: 'widget')
+      end
+
+      it 'suggest_pipeline experiment disabled' do
+        allow(helper).to receive(:experiment_enabled?).with(:suggest_pipeline) { false }
+
+        expect_next_instance_of(MergeRequestSerializer) do |serializer|
+          expect(serializer).to receive(:represent).with(merge_request, { serializer: 'widget' })
+        end
+
+        helper.serialize_issuable(merge_request, serializer: 'widget')
+      end
+    end
+  end
 end

spec/serializers/merge_request_widget_entity_spec.rb

@@ -271,9 +271,7 @@ RSpec.describe MergeRequestWidgetEntity do
 
   describe 'user callouts' do
     context 'when suggest pipeline feature is enabled' do
-      before do
-        stub_experiment(suggest_pipeline: true)
-      end
+      subject { described_class.new(resource, request: request, experiment_enabled: :suggest_pipeline).as_json }
 
       it 'provides a valid path value for user callout path' do
         expect(subject[:user_callouts_path]).to eq '/-/user_callouts'
@@ -307,10 +305,6 @@ RSpec.describe MergeRequestWidgetEntity do
     end
 
     context 'when suggest pipeline feature is not enabled' do
-      before do
-        stub_experiment(suggest_pipeline: false)
-      end
-
       it 'provides no valid value for user callout path' do
         expect(subject[:user_callouts_path]).to be_nil
       end