Add StdLogger type

[pkieltyka]

When building community packages, developers use a variety of loggers. It's been proposed in Go 2 to have a common Logger interface, but the below will work quite well today.

As a suggestion, it would be nice to see this code added directly to the github.com/rs/zerolog package.

or perhaps as a method on the zerolog.Logger interface, returning a StdLogger() with the interface below.. I'm happy to add a PR for this too with either approach.

package zerolog

import (
	"fmt"
	stdlog "log"
	"os"
)

// Wraps a zerolog.Logger so its interoperable with Go's standard "log" package

var _ StdLogger = &stdlog.Logger{}

type StdLogger interface {
	Fatal(v ...interface{})
	Fatalf(format string, v ...interface{})
	Print(v ...interface{})
	Println(v ...interface{})
	Printf(format string, v ...interface{})
}

func StandardLogger(log Logger) StdLogger {
	return &stdLogger{log}
}

type stdLogger struct {
	log Logger
}

func (s *stdLogger) Fatal(v ...interface{}) {
	s.log.Fatal().Msg(fmt.Sprint(v...))
	os.Exit(1)
}

func (s *stdLogger) Fatalf(format string, v ...interface{}) {
	s.log.Fatal().Msg(fmt.Sprintf(format, v...))
	os.Exit(1)
}

func (s *stdLogger) Print(v ...interface{}) {
	s.log.Info().Msg(fmt.Sprint(v...))
}

func (s *stdLogger) Println(v ...interface{}) {
	s.log.Info().Msg(fmt.Sprintln(v...))
}

func (s *stdLogger) Printf(format string, v ...interface{}) {
	s.log.Info().Msg(fmt.Sprintf(format, v...))
}

[rs]

Can you please link the proposal?

[pkieltyka]

sure, golang/go#13182

[rs]

I see no conclusion on this issue and no interface agreed on.

[pkieltyka]

yea, its still in proposal stage for Go 2, but you can see the direction for a standard interface. Right now you could infer a standard interface in Go v1.x by this assertion var _ StdLogger = &stdlog.Logger{} where "stdlog" is really the stdlib "log" package with an alias.

I'm good either way, as I've solved this in my code but I think it would be a nice addition to zerolog. Logrus is compatible with the above btw.. for ex,

var _ StdLogger = &logrus.Logger{} // works

[rs]

We already have Print and Printf on Logger. I’m open to add all the std logger methods to the main type without adding a new type. Note they should be exposed on the zerolog/log package too.

[pkieltyka]

thanks @rs that would be a very nice help to clean up code in our microservices that use zerolog and integrate with community packages with the standard methods above

[dxvgef]

Good idea! If zerolog implementslog, you can completely replace it, very much looking forward to it!

[mitar]

You can currently redirect standard log into zerolog as documented in README.

And issue #571 is about support for new structured logging interface in Golang.

But there are still some methods found in stdlog missing in zerolog (Println, Fatalf, ...). Those could be added. But the bigger issue is that some existing methods in zerolog conflict with those in stdlog. For example, Fatal() exists, but it sets the log level to fatal, it does not accept any arguments.

So sadly I do not see a way how this could be done in a backwards compatible way?

[mitar]

Println has been added in #533.

[mitar]

But Fatalf has not yet. :-)