Populate pipeline with objects before creating it

app/services/ci/create_pipeline_service.rb

@@ -7,6 +7,7 @@ module Ci
                 Gitlab::Ci::Pipeline::Chain::Validate::Repository,
                 Gitlab::Ci::Pipeline::Chain::Validate::Config,
                 Gitlab::Ci::Pipeline::Chain::Skip,
+                Gitlab::Ci::Pipeline::Chain::Populate,
                 Gitlab::Ci::Pipeline::Chain::Create].freeze
 
     def execute(source, ignore_skip_ci: false, save_on_errors: true, trigger_request: nil, schedule: nil, &block)

app/services/ci/pipeline_trigger_service.rb

@@ -16,8 +16,8 @@ module Ci
 
       pipeline = Ci::CreatePipelineService.new(project, trigger.owner, ref: params[:ref])
         .execute(:trigger, ignore_skip_ci: true) do |pipeline|
-          pipeline.trigger_requests.create!(trigger: trigger)
-          create_pipeline_variables!(pipeline)
+          pipeline.trigger_requests.build(trigger: trigger)
+          pipeline.variables.build(variables)
         end
 
       if pipeline.persisted?
@@ -33,14 +33,10 @@ module Ci
       end
     end
 
-    def create_pipeline_variables!(pipeline)
-      return unless params[:variables]
-
-      variables = params[:variables].map do |key, value|
+    def variables
+      params[:variables].to_h.map do |key, value|
         { key: key, value: value }
       end
-
-      pipeline.variables.create!(variables)
     end
   end
 end

lib/gitlab/ci/pipeline/chain/create.rb

@@ -9,13 +9,6 @@ module Gitlab
             ::Ci::Pipeline.transaction do
               pipeline.save!
 
-              @command.seeds_block&.call(pipeline)
-
-              pipeline.stage_seeds.each do |seed|
-                seed.user = current_user
-                seed.to_resource.save!
-              end
-
               # TODO populate environments with find_or_initialize_by in the chain too.
 
               ##

lib/gitlab/ci/pipeline/chain/populate.rb

+module Gitlab
+  module Ci
+    module Pipeline
+      module Chain
+        class Populate < Chain::Base
+          PopulateError = Class.new(StandardError)
+
+          def perform!
+            ##
+            # Populate pipeline with seeds block.
+            #
+            # It comes from a block argument to CreatePipelineService#execute.
+            #
+            @command.seeds_block&.call(pipeline)
+
+            pipeline.stage_seeds.each do |seed|
+              seed.user = current_user
+
+              pipeline.stages << seed.to_resource
+            end
+
+            raise Populate::PopulateError if pipeline.persisted?
+          end
+
+          def break?
+            pipeline.persisted?
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/ci/pipeline/seed/stage.rb

@@ -37,8 +37,6 @@ module Gitlab
                   stage.builds << build
                 end
               end
-
-              @pipeline.stages << stage
             end
           end
         end

spec/lib/gitlab/ci/pipeline/seed/stage_spec.rb

@@ -79,5 +79,15 @@ describe Gitlab::Ci::Pipeline::Seed::Stage do
       expect(pipeline.stages)
         .to all(satisfy { |stage| stage.project.present? })
     end
+
+    it 'can not be persisted without explicit pipeline assignment' do
+      stage = subject.to_resource
+
+      pipeline.save!
+
+      expect(stage).not_to be_persisted
+      expect(pipeline.reload.stages.count).to eq 0
+      expect(pipeline.reload.builds.count).to eq 0
+    end
   end
 end