fix: lifecycle-safe logger teardown without global state

Store file handle per module, swap lifecycle logger before closing file,
return teardown errors, remove duplicate Module() func.

Co-authored-by: Cursor <cursoragent@cursor.com>

setup.go

@@ -0,0 +1,91 @@
+package applog
+
+import (
+	"errors"
+	"fmt"
+	"log/slog"
+	"os"
+	"time"
+
+	"gitea.auvem.com/go-toolkit/app"
+	"github.com/lmittmann/tint"
+	slogmulti "github.com/samber/slog-multi"
+)
+
+type moduleState struct {
+	opts           AppLogOpts
+	logfile        *os.File
+	consoleHandler slog.Handler
+}
+
+func (s *moduleState) setup(m *app.Module) error {
+	if s.opts.FileOutput == "" && s.opts.ConsoleOutput == nil {
+		return fmt.Errorf("no logging output configured")
+	}
+
+	handlers := make([]slog.Handler, 0, 2)
+
+	if s.opts.FileOutput != "" {
+		f, err := os.OpenFile(s.opts.FileOutput, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
+		if err != nil {
+			return err
+		}
+		s.logfile = f
+
+		fileLevel := s.opts.FileLevel
+		if fileLevel == 0 && s.opts.ConsoleOutput == nil {
+			fileLevel = slog.LevelInfo
+		}
+		handlers = append(handlers, slog.NewJSONHandler(f, &slog.HandlerOptions{Level: fileLevel}))
+	}
+
+	if s.opts.ConsoleOutput != nil {
+		consoleLevel := s.opts.ConsoleLevel
+		if consoleLevel == 0 {
+			consoleLevel = slog.LevelInfo
+		}
+		s.consoleHandler = tint.NewHandler(s.opts.ConsoleOutput, &tint.Options{
+			Level:      consoleLevel,
+			TimeFormat: time.Kitchen,
+		})
+		handlers = append(handlers, s.consoleHandler)
+	}
+
+	logger := slog.New(slogmulti.Fanout(handlers...))
+	m.Lifecycle().WithLogger(logger)
+
+	if s.opts.SetDefault {
+		slog.SetDefault(logger)
+	}
+
+	if !s.opts.DisableAnnouncement {
+		logger.Info("Logger initialized", "module", ModuleName)
+	}
+
+	return nil
+}
+
+func (s *moduleState) teardown(lifecycle *app.Lifecycle) error {
+	if lifecycle != nil {
+		switch {
+		case s.consoleHandler != nil:
+			lifecycle.WithLogger(slog.New(s.consoleHandler))
+		default:
+			lifecycle.WithLogger(slog.New(slog.DiscardHandler))
+		}
+	}
+
+	if s.logfile == nil {
+		return nil
+	}
+
+	var err error
+	if syncErr := s.logfile.Sync(); syncErr != nil {
+		err = fmt.Errorf("flush log file: %w", syncErr)
+	}
+	if closeErr := s.logfile.Close(); closeErr != nil {
+		err = errors.Join(err, fmt.Errorf("close log file: %w", closeErr))
+	}
+	s.logfile = nil
+	return err
+}