1 files changed, 40 insertions, 0 deletions
diff --git a/rubocop/cop/graphql/json_type.rb b/rubocop/cop/graphql/json_type.rb
new file mode 100644
index 00000000000..1e3e3d7a7ff
--- /dev/null
+++ b/rubocop/cop/graphql/json_type.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# This cop checks for use of GraphQL::Types::JSON types in GraphQL fields
+# and arguments.
+#
+# @example
+#
+#   # bad
+#   class AwfulClass
+#     field :some_field, GraphQL::Types::JSON
+#   end
+#
+#   # good
+#   class GreatClass
+#     field :some_field, GraphQL::STRING_TYPE
+#   end
+
+module RuboCop
+  module Cop
+    module Graphql
+      class JSONType < RuboCop::Cop::Cop
+        MSG = 'Avoid using GraphQL::Types::JSON. See: ' \
+              'https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#json'.freeze
+
+        def_node_matcher :has_json_type?, <<~PATTERN
+          (send nil? {:field :argument}
+            (sym _)
+            (const
+              (const
+                (const nil? :GraphQL) :Types) :JSON)
+            (...)?)
+        PATTERN
+
+        def on_send(node)
+          add_offense(node, location: :expression) if has_json_type?(node)
+        end
+      end
+    end
+  end
+end