Support passing bridge variables to downstream pipeline

ee/app/models/ee/ci/bridge.rb

@@ -6,7 +6,11 @@ module EE
       extend ActiveSupport::Concern
 
       prepended do
-        serialize :options # rubocop:disable Cop/ActiveRecordSerialize
+        # rubocop:disable Cop/ActiveRecordSerialize
+        serialize :options
+        serialize :yaml_variables, ::Gitlab::Serializer::Ci::Variables
+        # rubocop:enable Cop/ActiveRecordSerialize
+
         has_many :sourced_pipelines, class_name: ::Ci::Sources::Pipeline,
                                      foreign_key: :source_job_id
 
@@ -34,6 +38,10 @@ module EE
       def target_ref
         options&.dig(:trigger, :branch)
       end
+
+      def downstream_variables
+        yaml_variables.map { |hash| hash.except(:public) }
+      end
     end
   end
 end

ee/app/services/ci/create_cross_project_pipeline_service.rb

@@ -43,6 +43,10 @@ module Ci
             source_project: @bridge.project,
             project: target_project,
             pipeline: pipeline)
+
+          # TODO we should use metadata with bridge jobs too.
+          #
+          pipeline.variables.build(@bridge.downstream_variables)
         end
     end
 

ee/spec/services/ci/create_cross_project_pipeline_service_spec.rb

@@ -141,5 +141,18 @@ describe Ci::CreateCrossProjectPipelineService, '#execute' do
         expect(bridge.failure_reason).to eq 'invalid_bridge_trigger'
       end
     end
+
+    context 'when bridge job has YAML variables defined' do
+      before do
+        bridge.yaml_variables = [{ key: 'BRIDGE', value: 'var', public: true }]
+      end
+
+      it 'passes bridge variables to downstream pipeline' do
+        pipeline = service.execute(bridge)
+
+        expect(pipeline.variables.first)
+          .to have_attributes(key: 'BRIDGE', value:'var')
+      end
+    end
   end
 end