Fallback when no logger is defined, fix default level (#255)

Fixes #254

main.go

@@ -415,7 +415,7 @@ func main() {
 
 	rootCmd.PersistentFlags().StringVarP(&logFormat, "log-format", "f", "text",
 		"Format in which to log")
-	rootCmd.PersistentFlags().StringVarP(&logLevel, "log-level", "l", "fatal",
+	rootCmd.PersistentFlags().StringVarP(&logLevel, "log-level", "l", "warning",
 		"Level at which to log")
 	rootCmd.PersistentFlags().BoolVar(&logDebug, "log-debug", false,
 		"Enable verbose source debug logging")

pkg/berglas/logging/levels.go

@@ -79,7 +79,7 @@ func LookupLevel(name string) (slog.Level, error) {
 		return LevelNotice, nil
 	case levelWarningName, "WARN": // "WARN" maintains compat with old logger
 		return LevelWarning, nil
-	case levelErrorName, "ERR": // "ERR" maintains compat with old logger
+	case levelErrorName, "ERR", "FATAL": // "ERR" and "FATAL" maintains compat with old logger
 		return LevelError, nil
 	case levelEmergencyName:
 		return LevelEmergency, nil

pkg/berglas/logging/logging.go

@@ -25,7 +25,9 @@ import (
 	"io"
 	"log/slog"
 	"math"
+	"os"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -35,6 +37,14 @@ type contextKey string
 // loggerKey points to the value in the context where the logger is stored.
 const loggerKey = contextKey("logger")
 
+var defaultLoggerOnce = sync.OnceValue(func() *slog.Logger {
+	l, err := New(os.Stderr, "warning", "json", false)
+	if err != nil {
+		panic(fmt.Errorf("failed to create logger: %w", err))
+	}
+	return l
+})
+
 // New creates a new logger in the specified format and writes to the provided
 // writer at the provided level. Use the returned leveler to dynamically change
 // the level to a different value after creation.
@@ -107,7 +117,8 @@ func FromContext(ctx context.Context) *slog.Logger {
 	if logger, ok := ctx.Value(loggerKey).(*slog.Logger); ok {
 		return logger
 	}
-	panic("no logger in context")
+
+	return defaultLoggerOnce()
 }
 
 // cloudLoggingAttrsEncoder updates the [slog.Record] attributes to match the