Remove `ci_dag_support` feature flag

app/models/ci/build_dependencies.rb

@@ -67,7 +67,6 @@ module Ci
     end
 
     def from_needs(scope)
-      return scope unless Feature.enabled?(:ci_dag_support, project, default_enabled: true)
       return scope unless processable.scheduling_type_dag?
 
       needs_names = processable.needs.artifacts.select(:name)

app/models/ci/processable.rb

@@ -25,8 +25,6 @@ module Ci
     end
 
     def self.select_with_aggregated_needs(project)
-      return all unless Feature.enabled?(:ci_dag_support, project, default_enabled: true)
-
       aggregated_needs_names = Ci::BuildNeed
         .scoped_build
         .select("ARRAY_AGG(name)")

app/services/ci/pipeline_processing/atomic_processing_service.rb

@@ -93,7 +93,7 @@ module Ci
       end
 
       def processable_status(processable)
-        if Feature.enabled?(:ci_dag_support, project, default_enabled: true) && processable.scheduling_type_dag?
+        if processable.scheduling_type_dag?
           # Processable uses DAG, get status of all dependent needs
           @collection.status_for_names(processable.aggregated_needs_names.to_a)
         else

app/services/ci/pipeline_processing/legacy_processing_service.rb

@@ -43,8 +43,6 @@ module Ci
       end
 
       def process_dag_builds_without_needs
-        return false unless Feature.enabled?(:ci_dag_support, project, default_enabled: true)
-
         created_processables.scheduling_type_dag.without_needs.each do |build|
           process_build(build, 'success')
         end
@@ -52,7 +50,6 @@ module Ci
 
       def process_dag_builds_with_needs(trigger_build_ids)
         return false unless trigger_build_ids.present?
-        return false unless Feature.enabled?(:ci_dag_support, project, default_enabled: true)
 
         # we find processables that are dependent:
         # 1. because of current dependency,
@@ -110,11 +107,7 @@ module Ci
       end
 
       def created_stage_scheduled_processables
-        if Feature.enabled?(:ci_dag_support, project, default_enabled: true)
-          created_processables.scheduling_type_stage
-        else
-          created_processables
-        end
+        created_processables.scheduling_type_stage
       end
 
       def created_processables

changelogs/unreleased/remove_ci_dag_support_feature_flag.yml

+---
+title: Remove `ci_dag_support` feature flag
+merge_request: 28863
+author: Lee Tickett
+type: added

doc/ci/directed_acyclic_graph/index.md

@@ -4,7 +4,7 @@ type: reference
 
 # Directed Acyclic Graph
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/issues/47063) in GitLab 12.2 (enabled by `ci_dag_support` feature flag).
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/issues/47063) in GitLab 12.2.
 
 A [directed acyclic graph](https://www.techopedia.com/definition/5739/directed-acyclic-graph-dag) can be
 used in the context of a CI/CD pipeline to build relationships between jobs such that

spec/models/ci/build_dependencies_spec.rb

@@ -96,14 +96,6 @@ describe Ci::BuildDependencies do
         end
 
         it { is_expected.to contain_exactly(build, rspec_test, staging) }
-
-        context 'when ci_dag_support is disabled' do
-          before do
-            stub_feature_flags(ci_dag_support: false)
-          end
-
-          it { is_expected.to contain_exactly(build, rspec_test, rubocop_test, staging) }
-        end
       end
 
       context 'when need artifacts are defined' do

spec/models/ci/processable_spec.rb

@@ -25,20 +25,6 @@ describe Ci::Processable do
         it 'returns all needs' do
           expect(with_aggregated_needs.first.aggregated_needs_names).to contain_exactly('test1', 'test2')
         end
-
-        context 'with ci_dag_support disabled' do
-          before do
-            stub_feature_flags(ci_dag_support: false)
-          end
-
-          it 'returns all processables' do
-            expect(with_aggregated_needs).to contain_exactly(processable)
-          end
-
-          it 'returns empty needs' do
-            expect(with_aggregated_needs.first.aggregated_needs_names).to be_nil
-          end
-        end
       end
 
       context 'without needs' do

spec/services/ci/pipeline_processing/shared_processing_service.rb

@@ -757,73 +757,19 @@ shared_examples 'Pipeline Processing Service' do
       expect(builds.pending).to contain_exactly(deploy)
     end
 
-    context 'when feature ci_dag_support is disabled' do
-      before do
-        stub_feature_flags(ci_dag_support: false)
-      end
-
-      it 'when linux:build finishes first it follows stages' do
-        expect(process_pipeline).to be_truthy
-
-        expect(stages).to eq(%w(pending created created))
-        expect(builds.pending).to contain_exactly(linux_build, mac_build)
-
-        # we follow the single path of linux
-        linux_build.reset.success!
-
-        expect(stages).to eq(%w(running created created))
-        expect(builds.success).to contain_exactly(linux_build)
-        expect(builds.pending).to contain_exactly(mac_build)
-
-        mac_build.reset.success!
-
-        expect(stages).to eq(%w(success pending created))
-        expect(builds.success).to contain_exactly(linux_build, mac_build)
-        expect(builds.pending).to contain_exactly(
-          linux_rspec, linux_rubocop, mac_rspec, mac_rubocop)
-
-        linux_rspec.reset.success!
-        linux_rubocop.reset.success!
-        mac_rspec.reset.success!
-        mac_rubocop.reset.success!
-
-        expect(stages).to eq(%w(success success pending))
-        expect(builds.success).to contain_exactly(
-          linux_build, linux_rspec, linux_rubocop, mac_build, mac_rspec, mac_rubocop)
-        expect(builds.pending).to contain_exactly(deploy)
-      end
-    end
-
     context 'when one of the jobs is run on a failure' do
       let!(:linux_notify) { create_build('linux:notify', stage: 'deploy', stage_idx: 2, when: 'on_failure', scheduling_type: :dag) }
 
       let!(:linux_notify_on_build) { create(:ci_build_need, build: linux_notify, name: 'linux:build') }
 
       context 'when another job in build phase fails first' do
-        context 'when ci_dag_support is enabled' do
-          it 'does skip linux:notify' do
-            expect(process_pipeline).to be_truthy
-
-            mac_build.reset.drop!
-            linux_build.reset.success!
-
-            expect(linux_notify.reset).to be_skipped
-          end
-        end
-
-        context 'when ci_dag_support is disabled' do
-          before do
-            stub_feature_flags(ci_dag_support: false)
-          end
-
-          it 'does run linux:notify' do
-            expect(process_pipeline).to be_truthy
+        it 'does skip linux:notify' do
+          expect(process_pipeline).to be_truthy
 
-            mac_build.reset.drop!
-            linux_build.reset.success!
+          mac_build.reset.drop!
+          linux_build.reset.success!
 
-            expect(linux_notify.reset).to be_pending
-          end
+          expect(linux_notify.reset).to be_skipped
         end
       end
 
@@ -864,19 +810,6 @@ shared_examples 'Pipeline Processing Service' do
         expect(stages).to eq(%w(success success running))
         expect(builds.pending).to contain_exactly(deploy)
       end
-
-      context 'when ci_dag_support is disabled' do
-        before do
-          stub_feature_flags(ci_dag_support: false)
-        end
-
-        it 'does run deploy_pages at the start' do
-          expect(process_pipeline).to be_truthy
-
-          expect(stages).to eq(%w(pending created created))
-          expect(builds.pending).to contain_exactly(linux_build, mac_build)
-        end
-      end
     end
   end