This is a proposal to add a method for converting a string to a Level. Here's an example:

func ParseLevel(level string) slog.Level {
	// convert string to Level ...
}

func main() {
	lvl := os.Getenv("LOG_LEVEL")
	level := ParseLevel(lvl)
	handler := slog.HandlerOptions{Level: level}.NewJSONHandler(os.Stdout)

	slog.SetDefault(slog.New(handler))
	slog.Info("hello world")
}

The benefit of providing this method is that, when using command-line or environment variables, I can specify the Level in string format without worrying about the specific numerical value of the Level. This kind of setting method is commonly found in various program startup parameters, such as:

./app -level=ERROR -output=./app.log

or

LOG_LEVEL=ERROR ./app (app just get level from os.Getenv("LOG_LEVEL") and set logger level)

I think the conversion effect of ParseLevel can be similar to:

// slog/level.go:60
func (l Level) String() string { // ... }

so the conversion effect as follows:

DEBUG -> Level(-4)
INFO -> Level(0)
WARN -> Level(4)
ERROR -> Level(8)
ERROR+2 -> LEVEL(10)
ERROR-2 -> LEVEL(6)
...