Validate against duplicates in job needs

Changelog: fixed

lib/gitlab/ci/yaml_processor.rb

@@ -86,11 +86,19 @@ module Gitlab
       def validate_job_needs!(name, job)
         return unless needs = job.dig(:needs, :job)
 
+        validate_duplicate_needs!(name, needs)
+
         needs.each do |need|
           validate_job_dependency!(name, need[:name], 'need')
         end
       end
 
+      def validate_duplicate_needs!(name, needs)
+        unless needs.uniq == needs
+          error!("#{name} has duplicate entries in the needs section.")
+        end
+      end
+
       def validate_job_dependency!(name, dependency, dependency_type = 'dependency')
         unless @jobs[dependency.to_sym]
           error!("#{name} job: undefined #{dependency_type}: #{dependency}")

spec/lib/gitlab/ci/yaml_processor_spec.rb

@@ -2097,6 +2097,12 @@ module Gitlab
           it_behaves_like 'returns errors', 'test1 job: need deploy is not defined in current or prior stages'
         end
 
+        context 'duplicate needs' do
+          let(:needs) { %w(build1 build1) }
+
+          it_behaves_like 'returns errors', 'test1 has duplicate entries in the needs section.'
+        end
+
         context 'needs and dependencies that are mismatching' do
           let(:needs) { %w(build1) }
           let(:dependencies) { %w(build2) }