Refactor ByStage job sorting

lib/travis/scheduler/limit/by_stage.rb

@@ -32,8 +32,9 @@ def queueable
           def jobs
             @jobs ||= begin
               # TODO would it make sense to cache these on `state`?
-              jobs = Job.where(source_id: job.source_id)
-              sort(jobs).map { |job| attrs(job) }
+              Job.where(source_id: job.source_id)
+                .sort_by(&:stage_number_parts)
+                .map(&method(:attrs))
             end
           end
 
@@ -45,15 +46,6 @@ def attrs(job)
             }
           end
 
-          def sort(jobs)
-            num = ->(job) { job.stage_number.split('.').map(&:to_i) }
-            jobs.sort { |lft, rgt| num.(lft) <=> num.(rgt) }
-          end
-
-          def stages
-            jobs.map { |job| job[:stage] }
-          end
-
           def report
             reports << MSGS[:max_stage] % ["build #{job.source_id}", job.stage.number, queueable.size]
           end

lib/travis/scheduler/record/job.rb

@@ -57,6 +57,10 @@ def finished?
     FINISHED_STATES.include?(state.try(:to_sym))
   end
 
+  def stage_number_parts
+    stage_number.split('.').map(&:to_i)
+  end
+
   def queueable=(value)
     if value
       queueable || create_queueable

spec/travis/scheduler/record/job_spec.rb

@@ -1,8 +1,12 @@
 describe Job do
   let(:config) { { rvm: '1.8.7' } }
-  let(:job) { FactoryGirl.create(:job, config: config).reload }
+  let(:job) { FactoryGirl.create(:job, config: config, stage_number: '1.2').reload }
 
   it 'deserializes config' do
     expect(job.config).to be_a(Hash)
   end
+
+  it 'renders its stage number numeric parts' do
+    expect(job.stage_number_parts).to eq [1, 2]
+  end
 end