1 files changed, 79 insertions, 0 deletions
diff --git a/rubocop/cop/graphql/enum_values.rb b/rubocop/cop/graphql/enum_values.rb
new file mode 100644
index 00000000000..71c42596334
--- /dev/null
+++ b/rubocop/cop/graphql/enum_values.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+# This cop enforces the enum value conventions from the enum style guide:
+# https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#enums
+#
+# @example
+#
+#   # bad
+#   class BadEnum < BaseEnum
+#     graphql_name 'Bad'
+#
+#     value 'foo'
+#   end
+#
+#   class UngoodEnum < BaseEnum
+#     graphql_name 'Ungood'
+#
+#     ['bar'].each do |val|
+#       value val
+#      end
+#   end
+#
+#   # good
+#   class GoodEnum < BaseEnum
+#     graphql_name 'Good'
+#
+#     value 'FOO'
+#   end
+#
+#   class GreatEnum < BaseEnum
+#     graphql_name 'Great'
+#
+#     ['bar'].each do |val|
+#       value val.upcase
+#      end
+#   end
+
+module RuboCop
+  module Cop
+    module Graphql
+      class EnumValues < RuboCop::Cop::Base
+        MSG = "Enum values must either be an uppercase string literal or uppercased with the `upcase` method. " \
+              "See https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#enums"
+
+        def_node_matcher :enum_value, <<~PATTERN
+          (send nil? :value $_ $...)
+        PATTERN
+
+        def_node_search :deprecated?, <<~PATTERN
+          (hash <(pair (sym :deprecated) _) ...>)
+        PATTERN
+
+        def_node_matcher :upcase_literal?, <<~PATTERN
+          (str #upcase?)
+        PATTERN
+
+        def_node_matcher :upcase_method?, <<~PATTERN
+          `(send _ :upcase)
+        PATTERN
+
+        def on_send(node)
+          value_node, params = enum_value(node)
+
+          return unless value_node
+          return if params.any? { deprecated?(_1) }
+          return if upcase_literal?(value_node) || upcase_method?(value_node)
+
+          add_offense(value_node)
+        end
+
+        private
+
+        def upcase?(str)
+          str == str.upcase
+        end
+      end
+    end
+  end
+end