func unsafeLogWith(err error, logger log.Logger) error {
// Handle errors implementing Err interface.
if ex, ok := err.(Err); ok {
logger.UnsafeFail(ex.Task())
hint := ex.Hint()
if next, ok := ex.Err().(Err); ok {
// The next error is also Err, call recursively
// after printing the hint when that is set.
logger.UnsafeStderr(hint)
return unsafeLogWith(next, logger)
} else {
// The next error is the root cause error.
// It is not implementing Err, so we can print
// the root cause error and stop the recursion.
last := ex.Err()
logger.UnsafeNewLine(fmt.Sprintf("(error = %v)", last))
logger.UnsafeStderr(hint)
return last
}
}
// Handle regular errors.
//
// This block is only executed when this function is called
// for the first time with an error not implementing Err.
logger.UnsafeFail("Unknown task")
logger.UnsafeNewLine(fmt.Sprintf("(error = %v)", err))
return err
}
// LogWith logs the given error using the given logger.
func LogWith(err error, logger log.Logger) error {
logger.Lock()
defer logger.Unlock()
return unsafeLogWith(err, logger)
}