Hide pipeline retry for Merge Trains

Merge Train pipelines cannot be restarted or they
will fail. This MR hide the retry button.

Closes https://gitlab.com/gitlab-org/gitlab/issues/14853

app/models/concerns/ci/pipeline_delegator.rb

@@ -15,7 +15,8 @@ module Ci
                :merge_request_ref?,
                :source_ref,
                :source_ref_slug,
-               :legacy_detached_merge_request_pipeline?, to: :pipeline
+               :legacy_detached_merge_request_pipeline?,
+               :merge_train_pipeline?, to: :pipeline
     end
   end
 end

doc/ci/merge_request_pipelines/pipelines_for_merged_results/merge_trains/index.md

@@ -122,6 +122,12 @@ is unavailable when
 Follow [this issue](https://gitlab.com/gitlab-org/gitlab/issues/12267) to
 track progress on this issue.
 
+### Merge Train Pipeline cannot be retried
+
+A Merge Train pipeline cannot be retried because the merge request is dropped from the merge train upon failure. For this reason, the retry button does not appear next to the pipeline icon.
+
+In the case of pipeline failure, you should [re-enqueue](#how-to-add-a-merge-request-to-a-merge-train) the merge request to the merge train, which will then initiate a new pipeline.
+
 ### Merge Train disturbs your workflow
 
 First of all, please check if [merge immediately](#immediately-merge-a-merge-request-with-a-merge-train)

ee/app/models/ee/ci/build.rb

@@ -107,6 +107,10 @@ module EE
         metrics_report
       end
 
+      def retryable?
+        !merge_train_pipeline? && super
+      end
+
       private
 
       def name_in?(names)

ee/app/models/ee/ci/pipeline.rb

@@ -98,6 +98,10 @@ module EE
         source_bridge&.dependent?
       end
 
+      def retryable?
+        !merge_train_pipeline? && super
+      end
+
       def update_bridge_status!
         raise ArgumentError unless bridge_triggered?
         raise BridgeStatusError unless source_bridge.active?

ee/changelogs/unreleased/14853-disable-pipeline-retry-button-for-merge-train-pipelines-for-merg.yml

+---
+title: Inactivate pipeline retries for Merge Trains
+merge_request: 17065
+author:
+type: added

ee/spec/features/merge_trains/user_adds_merge_request_to_merge_train_spec.rb

@@ -61,6 +61,25 @@ describe 'User adds a merge request to a merge train', :js do
       end
     end
 
+    context 'when pipeline for merge train succeeds' do
+      before do
+        visit project_merge_request_path(project, merge_request)
+        merge_request.merge_train.pipeline.builds.map(&:success!)
+      end
+
+      it 'displays pipeline control' do
+        expect(page).to have_selector('.mini-pipeline-graph-dropdown-toggle')
+      end
+
+      it 'does not allow retry for merge train pipeline' do
+        find('.mini-pipeline-graph-dropdown-toggle').click
+        page.within '.ci-job-component' do
+          expect(page).to have_selector('.ci-status-icon')
+          expect(page).not_to have_selector('.retry')
+        end
+      end
+    end
+
     context "when user clicks 'Remove from merge train' button" do
       before do
         click_link 'Remove from merge train'

ee/spec/models/ci/build_spec.rb

@@ -333,4 +333,22 @@ describe Ci::Build do
       end
     end
   end
+
+  describe '#retryable?' do
+    subject { build.retryable? }
+    let(:pipeline) { merge_request.all_pipelines.last }
+    let!(:build) { create(:ci_build, :canceled, pipeline: pipeline) }
+
+    context 'with pipeline for merged results' do
+      let(:merge_request) { create(:merge_request, :with_merge_request_pipeline) }
+
+      it { is_expected.to be true }
+    end
+
+    context 'with pipeline for merge train' do
+      let(:merge_request) { create(:merge_request, :on_train, :with_merge_train_pipeline) }
+
+      it { is_expected.to be false }
+    end
+  end
 end

ee/spec/models/ci/pipeline_spec.rb

@@ -527,4 +527,22 @@ describe Ci::Pipeline do
       it { is_expected.to be_falsy }
     end
   end
+
+  describe '#retryable?' do
+    subject { pipeline.retryable? }
+    let(:pipeline) { merge_request.all_pipelines.last }
+    let!(:build) { create(:ci_build, :canceled, pipeline: pipeline) }
+
+    context 'with pipeline for merged results' do
+      let(:merge_request) { create(:merge_request, :with_merge_request_pipeline) }
+
+      it { is_expected.to be true }
+    end
+
+    context 'with pipeline for merge train' do
+      let(:merge_request) { create(:merge_request, :on_train, :with_merge_train_pipeline) }
+
+      it { is_expected.to be false }
+    end
+  end
 end