module GraphQL::Backtrace::Tracer

def trace(key, metadata)
  push_data = case key
  when "lex", "parse"
    # No context here, don't have a query yet
    nil
  when "execute_multiplex", "analyze_multiplex"
    metadata[:multiplex].queries
  when "validate", "analyze_query", "execute_query", "execute_query_lazy"
    metadata[:query] || metadata[:queries]
  when "execute_field", "execute_field_lazy"
    metadata[:context]
  else
    # Custom key, no backtrace data for this
    nil
  end
  if push_data
    Thread.current[:last_graphql_backtrace_context] = push_data
  end
  if key == "execute_multiplex"
    begin
      yield
    rescue StandardError => err
      # This is an unhandled error from execution,
      # Re-raise it with a GraphQL trace.
      potential_context = Thread.current[:last_graphql_backtrace_context]
      if potential_context.is_a?(GraphQL::Query::Context) || potential_context.is_a?(GraphQL::Query::Context::FieldResolutionContext)
        raise TracedError.new(err, potential_context)
      else
        raise
      end
    ensure
      Thread.current[:last_graphql_backtrace_context] = nil
    end
  else
    yield
  end
end