http://facebook.github.io/graphql/#sec-Errors says

If an error can be associated to a particular field in the GraphQL result, it must contain an entry with the key path that details the path of the response field which experienced the error. This allows clients to identify whether a null result is intentional or caused by a runtime error.

This field should be a list of path segments starting at the root of the response and ending with the field associated with the error. Path segments that represent fields should be strings, and path segments that represent list indices should be 0‐indexed integers.

Currently this is not in place.

A PR nearly added this but its not quite right since it needs to be a list of path segments re: #304

The spec says :

"path": [ "hero", "heroFriends", 1, "name" ]