Implement GitLab QA release inflection strategy

qa/qa.rb

@@ -5,6 +5,7 @@ module QA
   # GitLab QA runtime classes, mostly singletons.
   #
   module Runtime
+    autoload :Release, 'qa/runtime/release'
     autoload :User, 'qa/runtime/user'
     autoload :Namespace, 'qa/runtime/namespace'
   end
@@ -81,3 +82,5 @@ module QA
     autoload :Runner, 'qa/specs/runner'
   end
 end
+
+QA::Runtime::Release.autoloads

qa/qa/runtime/release.rb

+module QA
+  module Runtime
+    ##
+    # Class that is responsible for plugging CE/EE extensions in, depending on
+    # environment variable GITLAB_RELEASE that should be present in the runtime
+    # environment.
+    #
+    # We need that to reduce the probability of conflicts when merging
+    # CE to EE.
+    #
+    class Release
+      UnspecifiedReleaseError = Class.new(StandardError)
+
+      def initialize(version = ENV['GITLAB_RELEASE'])
+        @version = version.to_s.upcase
+
+        unless %w[CE EE].include?(@version)
+          raise UnspecifiedReleaseError, 'GITLAB_RELEASE env not defined!'
+        end
+
+        begin
+          require "#{version.downcase}/strategy"
+        rescue LoadError
+          # noop
+        end
+      end
+
+      def has_strategy?
+        QA.const_defined?("#{@version}::Strategy")
+      end
+
+      def strategy
+        QA.const_get("#{@version}::Strategy")
+      end
+
+      def self.method_missing(name, *args)
+        @release ||= self.new
+
+        if @release.has_strategy?
+          @release.strategy.public_send(name, *args)
+        end
+      end
+    end
+  end
+end

qa/spec/runtime/release_spec.rb

+describe QA::Runtime::Release do
+  context 'when release version has extension strategy' do
+    subject { described_class.new('CE') }
+    let(:strategy) { spy('CE::Strategy') }
+
+    before do
+      stub_const('QA::CE::Strategy', strategy)
+    end
+
+    describe '#has_strategy?' do
+      it 'return true' do
+        expect(subject.has_strategy?).to be true
+      end
+    end
+
+    describe '#strategy' do
+      it 'return the strategy constant' do
+        expect(subject.strategy).to eq QA::CE::Strategy
+      end
+    end
+
+    describe 'delegated class methods' do
+      it 'delegates all calls to strategy class' do
+        described_class.some_method(1, 2)
+
+        expect(strategy).to have_received(:some_method)
+          .with(1, 2)
+      end
+    end
+  end
+
+  context 'when release version does not have extension strategy' do
+    subject { described_class.new('CE') }
+
+    describe '#has_strategy?' do
+      it 'returns false' do
+        expect(subject.has_strategy?).to be false
+      end
+    end
+
+    describe '#strategy' do
+      it 'raises error' do
+        expect { subject.strategy }.to raise_error(NameError)
+      end
+    end
+
+    describe 'delegated class methods' do
+      it 'behaves like a null object and does nothing' do
+        expect { described_class.some_method(2, 3) }.not_to raise_error
+      end
+    end
+  end
+
+  context 'when release version is invalid or unspecified' do
+    describe '#new' do
+      it 'raises an exception' do
+        expect { described_class.new(nil) }
+          .to raise_error(described_class::UnspecifiedReleaseError)
+      end
+    end
+  end
+end