multiwriter file logging

[yusufaine]

I'm glad that #71 fixed the colour issue, but was wondering if there was a way to allow logging to a file without said colour tags.

I currently have a logger setup like this:

writers := []io.Writer{os.Stderr}
if (logFile != "") {
    // open file
    writers = append(writers, fd)
}

ml := log.NewWithOptions(io.MultiWriter(wrs...), loggerOpts)
ml.SetColorProfile(termenv.TrueColor)
log.SetDefault(ml)

but the log file outputs as

�[1;38;5;86mINFO�[0m �[2m<crawler/crawler.go:68>�[0m visiting �[2mdepth�[0m�[2m=�[0m0 �[2mlink�[0m�[2m=�[0mhttps://example.com
�[1;38;5;86mINFO�[0m �[2m<crawler/crawler.go:68>�[0m visiting �[2mdepth�[0m�[2m=�[0m1 �[2mlink�[0m�[2m=�[0mhttps://www.iana.org/domains/example
�[1;38;5;86mINFO�[0m �[2m<crawler/crawler.go:68>�[0m visiting �[2mdepth�[0m�[2m=�[0m2 �

[aymanbagabas]

Hi @yusufaine, Log is meant to be used with one writer. Using SetColorProfile overrides the detected profile for the writer. Thus, using an io.MultiWriter will always disable the colors since the writer is not a terminal. Instead, you could wrap Log in a custom type that takes multiple writers and assigns each to its logger instance.

With this, if io.Writer is not a terminal, colors will be disabled.

type MultiLogger struct {
  writers []io.Writer
  loggers []*log.Logger
}

func NewMultiLogger(wrs ...io.Writer) *MultiLogger {
  ml := new(MultiLogger)
  ml.writers = make([]io.Writer, len(wrs))
  ml.loggers = make([]*log.Logger, len(wrs))
  for i, w := range wrs {
    ml.writer[i] = w
    ml.loggers[i] = log.New(w)
  }
  return ml
}

func (ml *MultiLogger) Info(msg any, kvs ...any) {
  for _, l := range ml.loggers {
    l.Info(msg, kvs...)
  }
}

[yusufaine]

Ah, I see... I've implemented a similar solution as well, thanks for this!

[cooperspencer]

I'd have a question for this specific approach, how'd you handle a log.Fatal here?

Because if I run a log.Fatal it would only write to one io.Writer

[yusufaine]

@cooperspencer A similar approach can be taken, iterate over the loggers with error severity and os.Exit(1) after all the iterations, similar to how it's already implemented.

https://github.com/charmbracelet/log/blob/main/logger.go#L371