Extract ensure stage service from commit status class

app/models/commit_status.rb

@@ -50,13 +50,9 @@ class CommitStatus < ActiveRecord::Base
   #
   # These are pages deployments and external statuses.
   #
-  before_create do |status|
-    next if status.stage_id.present? || importing?
-
-    ensure_pipeline_stage! do |stage|
-      status.run_after_commit do
-        StageUpdateWorker.perform_async(stage.id)
-      end
+  before_create unless: :importing? do
+    Ci::EnsureStageService.new(project, user).execute(self) do |stage|
+      self.run_after_commit { StageUpdateWorker.perform_async(stage.id) }
     end
   end
@@ -188,24 +184,4 @@ class CommitStatus < ActiveRecord::Base
       v =~ /\d+/ ? v.to_i : v
     end
   end
-
-  private
-
-  def ensure_pipeline_stage!
-    (find_stage || create_stage!).tap do |stage|
-      self.stage_id = stage.id
-
-      yield stage
-    end
-  end
-
-  def find_stage
-    pipeline.stages.find_by(name: stage)
-  end
-
-  def create_stage!
-    Ci::Stage.create!(name: stage,
-                      pipeline: pipeline,
-                      project: project)
-  end
 end

app/services/ci/ensure_stage_service.rb

+module Ci
+  ##
+  # We call this service everytime we persist a CI/CD job.
+  #
+  # In most cases a job should already have a stage assigned,  but in cases it
+  # doesn't have we need to either find existing one or create a brand new
+  # stage.
+  #
+  class EnsureStageService < BaseService
+    def execute(build)
+      @build = build
+
+      return if build.stage_id.present?
+      return if build.invalid?
+
+      ensure_stage.tap do |stage|
+        build.stage_id = stage.id
+
+        yield stage if block_given?
+      end
+    end
+
+    private
+
+    def ensure_stage
+      find_stage || create_stage
+    end
+
+    def find_stage
+      @build.pipeline.stages.find_by(name: @build.stage)
+    end
+
+    def create_stage
+      Ci::Stage.create!(name: @build.stage,
+                        pipeline: @build.pipeline,
+                        project: @build.project)
+    end
+  end
+end

spec/factories/commit_statuses.rb

 FactoryGirl.define do
   factory :commit_status, class: CommitStatus do
     name 'default'
+    stage 'test'
     status 'success'
     description 'commit status'
     pipeline factory: :ci_pipeline_with_one_job