zapcore: Add ParseLevel

zapcore/level.go

@@ -26,7 +26,10 @@ import (
 	"fmt"
 )
 
-var errUnmarshalNilLevel = errors.New("can't unmarshal a nil *Level")
+var (
+	errUnmarshalNilLevel = errors.New("can't unmarshal a nil *Level")
+	errInvalidLevel      = errors.New("invalid level")
+)
 
 // A Level is a logging priority. Higher levels are more important.
 type Level int8
@@ -55,6 +58,32 @@ const (
 	_maxLevel = FatalLevel
 )
 
+// LevelFromString returns a level based on the lower-case or all-caps ASCII
+// representation of the log level.
+//
+// This is particularly useful when dealing with text input to configure log
+// levels.
+func LevelFromString(text string) (Level, error) {
+	switch text {
+	case "debug", "DEBUG":
+		return DebugLevel, nil
+	case "info", "INFO", "": // make the zero value useful
+		return InfoLevel, nil
+	case "warn", "WARN":
+		return WarnLevel, nil
+	case "error", "ERROR":
+		return ErrorLevel, nil
+	case "dpanic", "DPANIC":
+		return DPanicLevel, nil
+	case "panic", "PANIC":
+		return PanicLevel, nil
+	case "fatal", "FATAL":
+		return FatalLevel, nil
+	default:
+		return -2, errInvalidLevel
+	}
+}
+
 // String returns a lower-case ASCII representation of the log level.
 func (l Level) String() string {
 	switch l {