Expose cross-project bridge jobs behind a feature flag

This adds a feature flag called `:cross_project_pipeline_triggers` and
makes it possible to fabricate a bridge job, from a CI/CD configuration,
when this feature flag is enabled.

ee/lib/ee/gitlab/ci/config/entry/jobs.rb

+# frozen_string_literal: true
+
+module EE
+  module Gitlab
+    module Ci
+      module Config
+        module Entry
+          module Jobs
+            extend ::Gitlab::Utils::Override
+
+            override :node_type
+            def node_type(name)
+              return ::Gitlab::Ci::Config::Entry::Hidden if hidden?(name)
+
+              if bridge?(name)
+                ::EE::Gitlab::Ci::Config::Entry::Bridge
+              else
+                ::Gitlab::Ci::Config::Entry::Job
+              end
+            end
+
+            def bridge?(name)
+              config.fetch(name).key?(:trigger) &&
+                cross_project_triggers_enabled?
+            end
+
+            def cross_project_triggers_enabled?
+              ::Feature.enabled?(:cross_project_pipeline_triggers, default_enabled: true)
+            end
+          end
+        end
+      end
+    end
+  end
+end

ee/spec/lib/gitlab/ci/config/entry/jobs_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Ci::Config::Entry::Jobs do
+  subject do
+    described_class.new(
+      {
+        '.hidden_job'.to_sym => { script: 'something' },
+        regular_job: { script: 'something' },
+        my_trigger: { trigger: 'my/project' }
+      }
+    )
+  end
+
+  context 'when cross-project pipeline triggers are enabled' do
+    before do
+      stub_feature_flags(cross_project_pipeline_triggers: true)
+    end
+
+    describe '#node_type' do
+      it 'correctly identifies hidden jobs' do
+        expect(subject.node_type(:'.hidden_job'))
+          .to eq ::Gitlab::Ci::Config::Entry::Hidden
+      end
+
+      it 'correctly identifies regular jobs' do
+        expect(subject.node_type(:regular_job))
+          .to eq ::Gitlab::Ci::Config::Entry::Job
+      end
+
+      it 'correctly identifies cross-project triggers' do
+        expect(subject.node_type(:my_trigger))
+          .to eq ::EE::Gitlab::Ci::Config::Entry::Bridge
+      end
+    end
+
+    describe '#bridge?' do
+      it 'returns true when a job is a trigger' do
+        expect(subject.bridge?(:my_trigger)).to be true
+      end
+
+      it 'returns false when a job is not a trigger' do
+        expect(subject.bridge?(:regular_job)).to be false
+      end
+    end
+  end
+
+  context 'when cross-project pipeline triggers are disabled' do
+    before do
+      stub_feature_flags(cross_project_pipeline_triggers: false)
+    end
+
+    describe '#node_type' do
+      it 'correctly identifies hidden jobs' do
+        expect(subject.node_type(:'.hidden_job'))
+          .to eq ::Gitlab::Ci::Config::Entry::Hidden
+      end
+
+      it 'correctly identifies regular jobs' do
+        expect(subject.node_type(:regular_job))
+          .to eq ::Gitlab::Ci::Config::Entry::Job
+      end
+
+      it 'does not identify trigger job as a bridge job' do
+        expect(subject.node_type(:my_trigger))
+          .to eq ::Gitlab::Ci::Config::Entry::Job
+      end
+    end
+
+    describe '#bridge?' do
+      it 'returns false even when a job is a trigger' do
+        expect(subject.bridge?(:my_trigger)).to be false
+      end
+
+      it 'returns false when a job is not a trigger' do
+        expect(subject.bridge?(:regular_job)).to be false
+      end
+    end
+  end
+end

lib/gitlab/ci/config/entry/jobs.rb

@@ -28,11 +28,15 @@ module Gitlab
             name.to_s.start_with?('.')
           end
 
+          def node_type(name)
+            hidden?(name) ? Entry::Hidden : Entry::Job
+          end
+
           # rubocop: disable CodeReuse/ActiveRecord
           def compose!(deps = nil)
             super do
               @config.each do |name, config|
-                node = hidden?(name) ? Entry::Hidden : Entry::Job
+                node = node_type(name)
 
                 factory = ::Gitlab::Config::Entry::Factory.new(node)
                   .value(config || {})
@@ -54,3 +58,6 @@ module Gitlab
     end
   end
 end
+
+::Gitlab::Ci::Config::Entry::Jobs
+  .prepend(::EE::Gitlab::Ci::Config::Entry::Jobs)