grails-data-graphql/plugin/grails-app/views/graphql/index.gson

import graphql.GraphQLError
import graphql.language.SourceLocation

model {
    Object data
    List<GraphQLError> errors
}

json {
    data g.render(data)
    if (errors) {
        errors(errors) { GraphQLError error ->
            message error.message
            errorType error.errorType
            locations(error.locations ?: []) { SourceLocation location ->
                line location.line
                column location.column
            }
        }
    }
}