gcp: avoid type assertion panic (#29)

Signed-off-by: Jason Hall <[email protected]>

gcp/setup.go

@@ -26,8 +26,8 @@ func NewHandler(level slog.Level) *Handler {
 				a.Key = "logging.googleapis.com/sourceLocation"
 			} else if a.Key == slog.LevelKey {
 				a.Key = "severity"
-				level := a.Value.Any().(slog.Level)
-				if level == LevelCritical {
+				level, ok := a.Value.Any().(slog.Level)
+				if ok && level == LevelCritical {
 					a.Value = slog.StringValue("CRITICAL")
 				}
 			}

gcp/setup_test.go

@@ -0,0 +1,19 @@
+package gcp
+
+import (
+	"context"
+	"log/slog"
+	"testing"
+)
+
+func TestHandler(t *testing.T) {
+	ctx := context.Background()
+	l := slog.New(NewHandler(slog.LevelInfo))
+	l.With("level", "INFO").Log(ctx, slog.LevelInfo, "hello world") // okay
+	l.With("level", "INFO").Log(ctx, slog.LevelWarn, "hello world") // weird, but okay (info)
+
+	// These should not panic.
+	l.With("level", nil).Log(ctx, slog.LevelInfo, "hello world")
+	l.With("level", 123).Log(ctx, slog.LevelInfo, "hello world")
+	l.With("level", map[string]string{}).Log(ctx, slog.LevelInfo, "hello world")
+}