Function New

app.go:422–522

New creates and initializes an App, immediately executing any functions registered via [Invoke] options. See the documentation of the App struct for details on the application's initialization, startup, and shutdown logic.

(opts ...Option)

// registered via [Invoke] options. See the documentation of the App struct for
// details on the application's initialization, startup, and shutdown logic.
func New(opts ...Option) *App {
	logger := fxlog.DefaultLogger(os.Stderr)

	app := &App{
		clock:        fxclock.System,
		startTimeout: DefaultTimeout,
		stopTimeout:  DefaultTimeout,
		receivers:    newSignalReceivers(),
	}
	app.root = &module{
		app: app,
		// We start with a logger that writes to stderr. One of the
		// following three things can change this:
		//
		// - fx.Logger was provided to change the output stream
		// - fx.WithLogger was provided to change the logger
		//   implementation
		// - Both, fx.Logger and fx.WithLogger were provided
		//
		// The first two cases are straightforward: we use what the
		// user gave us. For the last case, however, we need to fall
		// back to what was provided to fx.Logger if fx.WithLogger
		// fails.
		log:   logger,
		trace: []string{fxreflect.CallerStack(1, 2)[0].String()},
	}

	for _, opt := range opts {
		opt.apply(app.root)
	}

	// There are a few levels of wrapping on the lifecycle here. To quickly
	// cover them:
	//
	// - lifecycleWrapper ensures that we don't unintentionally expose the
	//   Start and Stop methods of the internal lifecycle.Lifecycle type
	// - lifecycleWrapper also adapts the internal lifecycle.Hook type into
	//   the public fx.Hook type.
	// - appLogger ensures that the lifecycle always logs events to the
	//   "current" logger associated with the fx.App.
	app.lifecycle = &lifecycleWrapper{
		lifecycle.New(appLogger{app}, app.clock),
	}

	containerOptions := []dig.Option{
		dig.DeferAcyclicVerification(),
		dig.DryRun(app.validate),
	}

	if app.recoverFromPanics {
		containerOptions = append(containerOptions, dig.RecoverFromPanics())
	}

	app.container = dig.New(containerOptions...)
	app.root.build(app, app.container)

	// Provide Fx types first to increase the chance a custom logger
	// can be successfully built in the face of unrelated DI failure.