1 files changed, 87 insertions, 0 deletions
diff --git a/rubocop/cop/graphql/enum_names.rb b/rubocop/cop/graphql/enum_names.rb
new file mode 100644
index 00000000000..74847cb8d17
--- /dev/null
+++ b/rubocop/cop/graphql/enum_names.rb
@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+# This cop enforces the enum naming conventions from the enum style guide:
+# https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#enums
+#
+# @example
+#
+#   # bad
+#   class FooBar < BaseEnum
+#     value 'FOO'
+#   end
+#
+#   class SubparEnum < BaseEnum
+#   end
+#
+#   class UngoodEnum < BaseEnum
+#     graphql_name 'UngoodEnum'
+#   end
+#
+#   # good
+#
+#   class GreatEnum < BaseEnum
+#     graphql_name 'Great'
+#
+#     value 'BAR'
+#   end
+#
+#   class NiceEnum < BaseEnum
+#     declarative_enum NiceDeclarativeEnum
+#   end
+
+module RuboCop
+  module Cop
+    module Graphql
+      class EnumNames < RuboCop::Cop::Base
+        SEE_SG_MSG = "See https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#enums"
+        CLASS_NAME_SUFFIX_MSG = "Enum class names must end with `Enum`. #{SEE_SG_MSG}"
+        GRAPHQL_NAME_MISSING_MSG = "A `graphql_name` must be defined for a GraphQL enum. #{SEE_SG_MSG}"
+        GRAPHQL_NAME_WITH_ENUM_MSG = "The `graphql_name` must not contain the string \"Enum\". #{SEE_SG_MSG}"
+
+        def_node_matcher :enum_subclass, <<~PATTERN
+          (class $(const nil? _) (const {nil? cbase} /.*Enum$/) ...)
+        PATTERN
+
+        def_node_search :find_graphql_name, <<~PATTERN
+          (... `(send nil? :graphql_name $(...)) ...)
+        PATTERN
+
+        def_node_search :declarative_enum?, <<~PATTERN
+          (... (send nil? :declarative_enum ...) ...)
+        PATTERN
+
+        def on_class(node)
+          const_node = enum_subclass(node)
+          return unless const_node
+
+          check_class_name(const_node)
+          check_graphql_name(node)
+        end
+
+        private
+
+        def check_class_name(const_node)
+          return unless const_node&.const_name
+          return if const_node.const_name.end_with?('Enum')
+
+          add_offense(const_node, message: CLASS_NAME_SUFFIX_MSG)
+        end
+
+        def check_graphql_name(node)
+          graphql_name_node = find_graphql_name(node)&.first
+
+          if graphql_name_node
+            return unless graphql_name_node&.str_content
+            return unless graphql_name_node.str_content.downcase.include?('enum')
+
+            add_offense(graphql_name_node, message: GRAPHQL_NAME_WITH_ENUM_MSG)
+          else
+            return if declarative_enum?(node)
+
+            add_offense(node, message: GRAPHQL_NAME_MISSING_MSG)
+          end
+        end
+      end
+    end
+  end
+end