Clear pipeline status cache after destruction of pipeline

`project.pipeline_status.has_status?` is cached, which can lead to Error
500s in the UI if the this condition is used to check whether a pipeline
exists for a commit. We now expire the cache to ensure that the
information is consistent.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/59453

app/services/ci/destroy_pipeline_service.rb

@@ -6,6 +6,8 @@ module Ci
       raise Gitlab::Access::AccessDeniedError unless can?(current_user, :destroy_pipeline, pipeline)
 
       pipeline.destroy!
+
+      Gitlab::Cache::Ci::ProjectPipelineStatus.new(pipeline.project).delete_from_cache
     end
   end
 end

changelogs/unreleased/sh-clear-pipeline-status-cache-upon-destroy.yml

+---
+title: Clear pipeline status cache after destruction of pipeline
+merge_request: 26575
+author:
+type: fixed

spec/services/ci/destroy_pipeline_service_spec.rb

@@ -3,8 +3,8 @@
 require 'spec_helper'
 
 describe ::Ci::DestroyPipelineService do
-  let(:project) { create(:project) }
-  let!(:pipeline) { create(:ci_pipeline, project: project) }
+  let(:project) { create(:project, :repository) }
+  let!(:pipeline) { create(:ci_pipeline, :success, project: project, sha: project.commit.id) }
 
   subject { described_class.new(project, user).execute(pipeline) }
 
@@ -17,6 +17,17 @@ describe ::Ci::DestroyPipelineService do
       expect { pipeline.reload }.to raise_error(ActiveRecord::RecordNotFound)
     end
 
+    it 'clears the cache', :use_clean_rails_memory_store_caching do
+      create(:commit_status, :success, pipeline: pipeline, ref: pipeline.ref)
+
+      expect(project.pipeline_status.has_status?).to be_truthy
+
+      subject
+
+      # Need to use find to avoid memoization
+      expect(Project.find(project.id).pipeline_status.has_status?).to be_falsey
+    end
+
     it 'does not log an audit event' do
       expect { subject }.not_to change { SecurityEvent.count }
     end