Avoid adding more than one foreign key within `with_lock_retries`

rubocop/cop/migration/with_lock_retries_disallowed_method.rb

@@ -29,9 +29,14 @@ module RuboCop
         ].sort.freeze
 
         MSG = "The method is not allowed to be called within the `with_lock_retries` block, the only allowed methods are: #{ALLOWED_MIGRATION_METHODS.join(', ')}"
+        MSG_ONLY_ONE_FK_ALLOWED = "Avoid adding more than one foreign key within the `with_lock_retries`. See https://docs.gitlab.com/ee/development/migration_style_guide.html#examples"
 
         def_node_matcher :send_node?, <<~PATTERN
-        send
+          send
+        PATTERN
+
+        def_node_matcher :add_foreign_key?, <<~PATTERN
+          (send nil? :add_foreign_key ...)
         PATTERN
 
         def on_block(node)
@@ -53,6 +58,17 @@ module RuboCop
 
           name = node.children[1]
           add_offense(node, location: :expression) unless ALLOWED_MIGRATION_METHODS.include?(name)
+          add_offense(node, location: :selector, message: MSG_ONLY_ONE_FK_ALLOWED) if multiple_fks?(node)
+        end
+
+        def multiple_fks?(node)
+          return unless add_foreign_key?(node)
+
+          count = node.parent.each_descendant(:send).count do |node|
+            add_foreign_key?(node)
+          end
+
+          count > 1
         end
       end
     end

spec/rubocop/cop/migration/with_lock_retries_disallowed_method_spec.rb

@@ -53,6 +53,22 @@ RSpec.describe RuboCop::Cop::Migration::WithLockRetriesDisallowedMethod, type: :
 
       expect(cop.offenses.size).to eq(0)
     end
+
+    describe 'for `add_foreign_key`' do
+      it 'registers an offense when more than two FKs are added' do
+        message = described_class::MSG_ONLY_ONE_FK_ALLOWED
+
+        expect_offense <<~RUBY
+          with_lock_retries do
+            add_foreign_key :imports, :projects, column: :project_id, on_delete: :cascade
+            ^^^^^^^^^^^^^^^ #{message}
+            add_column :projects, :name, :text
+            add_foreign_key :imports, :users, column: :user_id, on_delete: :cascade
+            ^^^^^^^^^^^^^^^ #{message}
+          end
+        RUBY
+      end
+    end
   end
 
   context 'outside of migration' do