Properly implement prepending for Concern

1 files changed, 121 insertions, 0 deletions

diff --git a/spec/lib/gitlab/patch/prependable_spec.rb b/spec/lib/gitlab/patch/prependable_spec.rb
new file mode 100644
index 00000000000..1c90a24c0e8
--- /dev/null
+++ b/spec/lib/gitlab/patch/prependable_spec.rb
@@ -0,0 +1,121 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+# Patching ActiveSupport::Concern
+require_relative '../../../../config/initializers/0_as_concern'
+
+describe Gitlab::Patch::Prependable do
+  let(:prepended_modules) { [] }
+
+  let(:ee) do
+    # So that block in Module.new could see them
+    prepended_modules_ = prepended_modules
+
+    Module.new do
+      extend ActiveSupport::Concern
+
+      class_methods do
+        def class_name
+          super.tr('C', 'E')
+        end
+      end
+
+      this = self
+      prepended do
+        prepended_modules_ << this
+      end
+
+      def name
+        super.tr('c', 'e')
+      end
+    end
+  end
+
+  let(:ce) do
+    prepended_modules_ = prepended_modules
+    ee_ = ee
+
+    Module.new do
+      extend ActiveSupport::Concern
+      prepend ee_
+
+      class_methods do
+        def class_name
+          'CE'
+        end
+      end
+
+      this = self
+      prepended do
+        prepended_modules_ << this
+      end
+
+      def name
+        'ce'
+      end
+    end
+  end
+
+  describe 'a class including a concern prepending a concern' do
+    subject { Class.new.include(ce) }
+
+    it 'returns values from prepended module ee' do
+      expect(subject.new.name).to eq('ee')
+      expect(subject.class_name).to eq('EE')
+    end
+
+    it 'prepends only once' do
+      ce.prepend(ee)
+      ce.prepend(ee)
+
+      subject
+
+      expect(prepended_modules).to eq([ee, ce])
+    end
+  end
+
+  describe 'a class prepending a concern prepending a concern' do
+    subject { Class.new.prepend(ce) }
+
+    it 'returns values from prepended module ce' do
+      expect(subject.new.name).to eq('ce')
+      expect(subject.class_name).to eq('CE')
+    end
+
+    it 'prepends only once' do
+      subject.prepend(ce)
+
+      expect(prepended_modules).to eq([ee, ce])
+    end
+  end
+
+  describe 'a class prepending a concern' do
+    subject do
+      ee_ = ee
+
+      Class.new do
+        prepend ee_
+
+        def self.class_name
+          'CE'
+        end
+
+        def name
+          'ce'
+        end
+      end
+    end
+
+    it 'returns values from prepended module ee' do
+      expect(subject.new.name).to eq('ee')
+      expect(subject.class_name).to eq('EE')
+    end
+
+    it 'prepends only once' do
+      subject.prepend(ee)
+
+      expect(prepended_modules).to eq([ee])
+    end
+  end
+end