Apply reviwer suggestions 2

Extract initialize_relative_positions into Board::Issues::ListService

app/controllers/boards/issues_controller.rb

@@ -27,9 +27,7 @@ module Boards
       list_service = Boards::Issues::ListService.new(board_parent, current_user, filter_params)
       issues = issues_from(list_service)
 
-      if Gitlab::Database.read_write? && !board.disabled_for?(current_user)
-        Issue.move_nulls_to_end(issues)
-      end
+      ::Boards::Issues::ListService.initialize_relative_positions(board, current_user, issues)
 
       render_issues(issues, list_service.metadata)
     end

app/graphql/resolvers/board_list_issues_resolver.rb

@@ -17,17 +17,11 @@ module Resolvers
       service = ::Boards::Issues::ListService.new(list.board.resource_parent, context[:current_user], filter_params)
       pagination_connections = Gitlab::Graphql::Pagination::Keyset::Connection.new(service.execute)
 
-      initialize_relative_positions(pagination_connections.items, list.board)
+      ::Boards::Issues::ListService.initialize_relative_positions(list.board, current_user, pagination_connections.items)
 
       pagination_connections
     end
 
-    def initialize_relative_positions(issues, board)
-      if Gitlab::Database.read_write? && !board.disabled_for?(current_user)
-        Issue.move_nulls_to_end(issues)
-      end
-    end
-
     # https://gitlab.com/gitlab-org/gitlab/-/issues/235681
     def self.complexity_multiplier(args)
       0.005

app/services/boards/issues/list_service.rb

@@ -9,6 +9,14 @@ module Boards
         IssuesFinder.valid_params
       end
 
+      # It is a class method because we cannot apply it
+      # prior to knowing how many items should be fetched for a list.
+      def self.initialize_relative_positions(board, current_user, issues)
+        if Gitlab::Database.read_write? && !board.disabled_for?(current_user)
+          Issue.move_nulls_to_end(issues)
+        end
+      end
+
       private
 
       def order(items)

spec/services/boards/issues/list_service_spec.rb

@@ -139,4 +139,51 @@ RSpec.describe Boards::Issues::ListService do
     end
     # rubocop: enable RSpec/MultipleMemoizedHelpers
   end
+
+  describe '.initialize_relative_positions' do
+    let_it_be(:user) { create(:user) }
+    let_it_be(:project) { create(:project, :empty_repo) }
+    let_it_be(:board) { create(:board, project: project) }
+    let_it_be(:backlog) { create(:backlog_list, board: board) }
+
+    let(:issue) { create(:issue, project: project, relative_position: nil) }
+
+    context "when 'Gitlab::Database::read_write?' is true" do
+      before do
+        allow(Gitlab::Database).to receive(:read_write?).and_return(true)
+      end
+
+      context 'user cannot move issues' do
+        it 'does not initialize the relative positions of issues' do
+          described_class.initialize_relative_positions(board, user, [issue])
+
+          expect(issue.relative_position).to eq nil
+        end
+      end
+
+      context 'user can move issues' do
+        before do
+          project.add_developer(user)
+        end
+
+        it 'initializes the relative positions of issues' do
+          described_class.initialize_relative_positions(board, user, [issue])
+
+          expect(issue.relative_position).not_to eq nil
+        end
+      end
+    end
+
+    context "when 'Gitlab::Database::read_write?' is false" do
+      before do
+        allow(Gitlab::Database).to receive(:read_write?).and_return(false)
+      end
+
+      it 'does not initialize the relative positions of issues' do
+        described_class.initialize_relative_positions(board, user, [issue])
+
+        expect(issue.relative_position).to eq nil
+      end
+    end
+  end
 end