Validate presence of a stage index in the model

app/models/ci/stage.rb

@@ -13,9 +13,12 @@ module Ci
     has_many :statuses, class_name: 'CommitStatus', foreign_key: :stage_id
     has_many :builds, foreign_key: :stage_id
 
-    validates :project, presence: true, unless: :importing?
-    validates :pipeline, presence: true, unless: :importing?
-    validates :name, presence: true, unless: :importing?
+    with_options unless: :importing? do
+      validates :project, presence: true
+      validates :pipeline, presence: true
+      validates :name, presence: true
+      validates :index, presence: true
+    end
 
     after_initialize do |stage|
       self.status = DEFAULT_STATUS if self.status.nil?

app/services/ci/ensure_stage_service.rb

@@ -42,6 +42,7 @@ module Ci
 
     def create_stage
       Ci::Stage.create!(name: @build.stage,
+                        index: @build.stage_idx,
                         pipeline: @build.pipeline,
                         project: @build.project)
     end

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

@@ -19,6 +19,7 @@ module Gitlab
 
           def attributes
             { name: @attributes.fetch(:name),
+              index: @attributes.fetch(:index),
               pipeline: @pipeline,
               project: @pipeline.project }
           end

spec/factories/ci/stages.rb

@@ -21,6 +21,7 @@ FactoryBot.define do
     pipeline factory: :ci_empty_pipeline
 
     name 'test'
+    index 1
     status 'pending'
   end
 end

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

@@ -24,7 +24,8 @@ describe Gitlab::Ci::Pipeline::Seed::Stage do
   describe '#attributes' do
     it 'returns hash attributes of a stage' do
       expect(subject.attributes).to be_a Hash
-      expect(subject.attributes).to include(:name, :project)
+      expect(subject.attributes)
+        .to include(:name, :index, :pipeline, :project)
     end
   end