Handle presenters in BasePolicy

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/policies/base_policy.rb

@@ -53,6 +53,10 @@ class BasePolicy
   def self.class_for(subject)
     return GlobalPolicy if subject.nil?
 
+    if subject.class.ancestors.include?(Gitlab::View::Presenter::Base)
+      subject = subject.subject
+    end
+
     subject.class.ancestors.each do |klass|
       next unless klass.name
 

spec/policies/base_policy_spec.rb

+require 'spec_helper'
+
+describe BasePolicy, models: true do
+  let(:build) { create(:ci_build) }
+
+  describe '.class_for' do
+    it 'detects policy class based on the subject ancestors' do
+      expect(described_class.class_for(build)).to eq(Ci::BuildPolicy)
+    end
+
+    it 'detects policy class for a presented subject' do
+      presentee = Ci::Build::Presenter.new(build)
+
+      expect(described_class.class_for(presentee)).to eq(Ci::BuildPolicy)
+    end
+  end
+end