Handle exceptions outside the GraphQL schema

This allows us to report JSON parse exceptions to clients and ignore
them in sentry.

1 files changed, 37 insertions, 0 deletions

diff --git a/lib/gitlab/graphql/variables.rb b/lib/gitlab/graphql/variables.rb
new file mode 100644
index 00000000000..ffbaf65b512
--- /dev/null
+++ b/lib/gitlab/graphql/variables.rb
@@ -0,0 +1,37 @@
+module Gitlab
+  module Graphql
+    class Variables
+      Invalid = Class.new(Gitlab::Graphql::StandardGraphqlError)
+
+      def initialize(param)
+        @param = param
+      end
+
+      def to_h
+        ensure_hash(@param)
+      end
+
+      private
+
+      # Handle form data, JSON body, or a blank value
+      def ensure_hash(ambiguous_param)
+        case ambiguous_param
+        when String
+          if ambiguous_param.present?
+            ensure_hash(JSON.parse(ambiguous_param))
+          else
+            {}
+          end
+        when Hash, ActionController::Parameters
+          ambiguous_param
+        when nil
+          {}
+        else
+          raise Invalid, "Unexpected parameter: #{ambiguous_param}"
+        end
+      rescue JSON::ParserError => e
+        raise Invalid.new(e)
+      end
+    end
+  end
+end