Extend Gitlab::Codeowners to include a method to return sections

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/232988

* Add method `.sections` to `Gitlab::CodeOwners`

ee/changelogs/unreleased/232988_add_sections_to_codeowners.yml

+---
+title: Extend Gitlab::Codeowners to include a method for returning the sections only
+merge_request: 48898
+author:
+type: added

ee/lib/gitlab/code_owners.rb

@@ -13,6 +13,15 @@ module Gitlab
       end
     end
 
+    # @param project [Project]
+    # @param ref [String]
+    # Fetch sections from CODEOWNERS file
+    def self.sections(project, ref)
+      return [] unless project.feature_available?(:code_owners)
+
+      Loader.new(project, ref, []).code_owners_sections
+    end
+
     # @param merge_request [MergeRequest]
     # @param merge_request_diff [MergeRequestDiff]
     #   Find code owners entries at a particular MergeRequestDiff.

ee/lib/gitlab/code_owners/file.rb

@@ -31,6 +31,10 @@ module Gitlab
         @blob&.path
       end
 
+      def sections
+        parsed_data.keys
+      end
+
       def entry_for_path(path)
         path = "/#{path}" unless path.start_with?('/')
 

ee/lib/gitlab/code_owners/loader.rb

@@ -41,6 +41,10 @@ module Gitlab
         code_owners_file&.path
       end
 
+      def code_owners_sections
+        code_owners_file&.sections
+      end
+
       private
 
       def load_bare_entries_for_paths

ee/spec/lib/gitlab/code_owners/file_spec.rb

@@ -153,6 +153,39 @@ RSpec.describe Gitlab::CodeOwners::File do
     end
   end
 
+  describe '#sections' do
+    subject { file.sections }
+
+    context 'when CODEOWNERS file contains sections' do
+      let(:file_content) do
+        <<~CONTENT
+        *.rb @ruby-owner
+
+        [Documentation]
+        *.md @gl-docs
+
+        [Test]
+        *_spec.rb @gl-test
+
+        [Documentation]
+        doc/* @gl-docs
+        CONTENT
+      end
+
+      it 'returns unique sections' do
+        is_expected.to match_array(%w[codeowners Documentation Test])
+      end
+    end
+
+    context 'when CODEOWNERS file is missing' do
+      let(:blob) { nil }
+
+      it 'returns a default section' do
+        is_expected.to match_array(['codeowners'])
+      end
+    end
+  end
+
   describe '#entry_for_path' do
     shared_examples_for "returns expected matches" do
       context 'for a path without matches' do

ee/spec/lib/gitlab/code_owners/loader_spec.rb

@@ -165,6 +165,28 @@ RSpec.describe Gitlab::CodeOwners::Loader do
     end
   end
 
+  describe '#code_owners_sections' do
+    subject { loader.code_owners_sections }
+
+    context 'when CODEOWNERS does not have sections' do
+      it { is_expected.to match_array(['codeowners']) }
+    end
+
+    context 'when CODEOWNERS contains sections' do
+      let(:codeowner_content) do
+        <<~CODEOWNERS
+        [Documentation]
+        docs/* @documentation-owner
+        docs/CODEOWNERS @owner-1 owner2@gitlab.org @owner-3 @documentation-owner
+        [Testing]
+        spec/* @test-owner @test-group @test-group/nested-group
+        CODEOWNERS
+      end
+
+      it { is_expected.to match_array(%w[codeowners Documentation Testing]) }
+    end
+  end
+
   describe '#empty_code_owners?' do
     context 'when file does not exist' do
       let(:codeowner_blob) { nil }

ee/spec/lib/gitlab/code_owners_spec.rb

@@ -44,6 +44,33 @@ RSpec.describe Gitlab::CodeOwners do
     end
   end
 
+  describe '.sections' do
+    subject { described_class.sections(project, branch) }
+
+    let(:branch) { TestEnv::BRANCH_SHA['with-codeowners'] }
+    let(:codeowner_lookup_ref) { branch }
+
+    context 'when the feature is available' do
+      before do
+        stub_licensed_features(code_owners: true)
+      end
+
+      it 'returns sections' do
+        is_expected.to match_array(['codeowners'])
+      end
+    end
+
+    context 'when the feature is not available' do
+      before do
+        stub_licensed_features(code_owners: false)
+      end
+
+      it 'returns empty array' do
+        is_expected.to be_empty
+      end
+    end
+  end
+
   describe ".fast_path_lookup and .slow_path_lookup" do
     let(:codeowner_lookup_ref) { merge_request.target_branch }
     let(:codeowner_content) { 'files/ruby/feature.rb @owner-1' }