Block execution of cyclical pipelines

Do not allow pipelines that reference one another
to execute infinitely

Changelog: fixed

app/services/ci/create_downstream_pipeline_service.rb

@@ -120,7 +120,6 @@ module Ci
     def has_cyclic_dependency?
       return false if @bridge.triggers_child_pipeline?
 
-      if Feature.enabled?(:ci_drop_cyclical_triggered_pipelines, @bridge.project, default_enabled: :yaml)
       pipeline_checksums = @bridge.pipeline.self_and_upstreams.filter_map do |pipeline|
         config_checksum(pipeline) unless pipeline.child?
       end
@@ -129,7 +128,6 @@ module Ci
       # fail when 2 cycles are detected: A -> B -> A -> B -> A
       pipeline_checksums.tally.any? { |_checksum, occurrences| occurrences > 2 }
     end
-    end
 
     def has_max_descendants_depth?
       return false unless @bridge.triggers_child_pipeline?

config/feature_flags/development/ci_drop_cyclical_triggered_pipelines.yml

----
-name: ci_drop_cyclical_triggered_pipelines
-introduced_by_url: https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/1195
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/329390
-milestone: '13.12'
-type: development
-group: group::pipeline execution
-default_enabled: false

spec/services/ci/create_downstream_pipeline_service_spec.rb

@@ -485,14 +485,6 @@ RSpec.describe Ci::CreateDownstreamPipelineService, '#execute' do
         end
 
         it_behaves_like 'detects cyclical pipelines'
-
-        context 'when ci_drop_cyclical_triggered_pipelines is not enabled' do
-          before do
-            stub_feature_flags(ci_drop_cyclical_triggered_pipelines: false)
-          end
-
-          it_behaves_like 'passes cyclical pipeline precondition'
-        end
       end
 
       context 'when source in the ancestry differ' do