1 files changed, 53 insertions, 0 deletions
diff --git a/lib/gitlab/graphql/negatable_arguments.rb b/lib/gitlab/graphql/negatable_arguments.rb
new file mode 100644
index 00000000000..b4ab31ed51a
--- /dev/null
+++ b/lib/gitlab/graphql/negatable_arguments.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module NegatableArguments
+      class TypeDefiner
+        def initialize(resolver_class, type_definition)
+          @resolver_class = resolver_class
+          @type_definition = type_definition
+        end
+
+        def define!
+          negated_params_type.instance_eval(&@type_definition)
+        end
+
+        def negated_params_type
+          @negated_params_type ||= existing_type || build_type
+        end
+
+        private
+
+        def existing_type
+          ::Types.const_get(type_class_name, false) if ::Types.const_defined?(type_class_name)
+        end
+
+        def build_type
+          klass = Class.new(::Types::BaseInputObject)
+          ::Types.const_set(type_class_name, klass)
+          klass
+        end
+
+        def type_class_name
+          @type_class_name ||= begin
+            base_name = @resolver_class.name.sub('Resolvers::', '')
+            base_name + 'NegatedParamsType'
+          end
+        end
+      end
+
+      def negated(param_key: :not, &block)
+        definer = ::Gitlab::Graphql::NegatableArguments::TypeDefiner.new(self, block)
+        definer.define!
+
+        argument param_key, definer.negated_params_type,
+                 required: false,
+                 description: <<~MD
+                     List of negated arguments.
+                     Warning: this argument is experimental and a subject to change in future.
+                 MD
+      end
+    end
+  end
+end