Fix slog nil pointer error (#3563)

The problem caused by the mistake in the newLogger function. The nil value is returned even with the valid log format.

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

cmd/dex/serve.go

@@ -520,11 +520,11 @@ func newLogger(level slog.Level, format string) (*slog.Logger, error) {
 	var handler slog.Handler
 	switch strings.ToLower(format) {
 	case "", "text":
-		slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
+		handler = slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
 			Level: level,
 		})
 	case "json":
-		slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
+		handler = slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
 			Level: level,
 		})
 	default:

cmd/dex/serve_test.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"log/slog"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewLogger(t *testing.T) {
+	t.Run("JSON", func(t *testing.T) {
+		logger, err := newLogger(slog.LevelInfo, "json")
+		require.NoError(t, err)
+		require.NotEqual(t, (*slog.Logger)(nil), logger)
+	})
+
+	t.Run("Text", func(t *testing.T) {
+		logger, err := newLogger(slog.LevelError, "text")
+		require.NoError(t, err)
+		require.NotEqual(t, (*slog.Logger)(nil), logger)
+	})
+
+	t.Run("Unknown", func(t *testing.T) {
+		logger, err := newLogger(slog.LevelError, "gofmt")
+		require.Error(t, err)
+		require.Equal(t, "log format is not one of the supported values (json, text): gofmt", err.Error())
+		require.Equal(t, (*slog.Logger)(nil), logger)
+	})
+}