Annotate Multiple methods that produce the same type

[UdamDewaraja]

Hello, would like some help on how to get started with fx. Relatively new to go as well.

I have an API server that I'm bootstrapping using go-chi. I have a method that returns a chi.Mux that feeds into another method that produces a higher-level chi.Mux which gets passed into the method that sets up the server. I've looked through many of the docs and I'm struggling to understand why this wouldn't work.
All this works if I don't use DI or partially use DI.

Methods are as follows:

func NewV1RoutesMux() *chi.Mux {
... 
}

func NewServerMux(v1ServerMux *chi.Mux) *chi.Mux {
...
}

// NewHTTPServer builds an HTTP server that will begin serving requests
// when the Fx application starts.
func NewHTTPServer(lc fx.Lifecycle, serverMux *chi.Mux) *http.Server {
    srv := &http.Server{Addr: ":8080", Handler: servermux}
	lc.Append(fx.Hook{
		OnStart: func(ctx context.Context) error {
			ln, err := net.Listen("tcp", srv.Addr)
			if err != nil {
				log.Fatal("Error serving router")
				return err
			}
			log.Println("Starting HTTP server at", srv.Addr)
			go srv.Serve(ln)
			return nil
		},
		OnStop: func(ctx context.Context) error {
			return srv.Shutdown(ctx)
		},
	})
	return srv
}

// main.go
func main() {
	fx.New(
		fx.Provide(
			fx.Annotate(router.NewHTTPServer, fx.ParamTags(`name:"serverMux"`)),
			fx.Annotate(router.NewServerMux, fx.ParamTags(`name:"v1ServerMux"`), fx.ResultTags(`name:"serverMux"`)),
			fx.Annotate(router.NewV1RoutesMux, fx.ResultTags(`name:"v1ServerMux"`)),
		),
		fx.Invoke(func(*http.Server) {}),
	).Run()
}

The error I get is:

[Fx] ERROR		fx.Invoke(main.main.func1()) called from:
main.main
	/Users/udam/Documents/projects/go-stuff/finsights-service/cmd/main.go:20
runtime.main
	/usr/local/go/src/runtime/proc.go:250
Failed: could not build arguments for function "main".main.func1
	/Users/udam/Documents/projects/go-stuff/finsights-service/cmd/main.go:20:
failed to build *http.Server:
missing dependencies for function "reflect".makeFuncStub
	/usr/local/go/src/reflect/asm_amd64.s:28:
missing types:
	- fx.Lifecycle[name="serverMux"] (did you mean to Provide it?)
	- *chi.Mux (did you mean to Provide it?)
[Fx] ERROR		Failed to start: could not build arguments for function "main".main.func1
	/Users/udam/Documents/projects/go-stuff/finsights-service/cmd/main.go:20:
failed to build *http.Server:
missing dependencies for function "reflect".makeFuncStub
	/usr/local/go/src/reflect/asm_amd64.s:28:
missing types:
	- fx.Lifecycle[name="serverMux"] (did you mean to Provide it?)
	- *chi.Mux (did you mean to Provide it?)

Any help would be much appreciated.

[sywhang]

@UdamDewaraja sorry for the delayed response. This looks like it has to do with the way which annotation is applied to an fx-injected parameter.

You could work around this problem by "skipping" the first parameter's annotation with an empty string tag:

func NewV1RoutesMux() *chi.Mux {
... 
}

func NewServerMux(v1ServerMux *chi.Mux) *chi.Mux {
...
}

// NewHTTPServer builds an HTTP server that will begin serving requests
// when the Fx application starts.
func NewHTTPServer(lc fx.Lifecycle, serverMux *chi.Mux) *http.Server {
    srv := &http.Server{Addr: ":8080", Handler: servermux}
	lc.Append(fx.Hook{
		OnStart: func(ctx context.Context) error {
			ln, err := net.Listen("tcp", srv.Addr)
			if err != nil {
				log.Fatal("Error serving router")
				return err
			}
			log.Println("Starting HTTP server at", srv.Addr)
			go srv.Serve(ln)
			return nil
		},
		OnStop: func(ctx context.Context) error {
			return srv.Shutdown(ctx)
		},
	})
	return srv
}

// main.go
func main() {
	fx.New(
		fx.Provide(
			fx.Annotate(router.NewHTTPServer, fx.ParamTags(`name:"serverMux"`)),
			fx.Annotate(router.NewServerMux, fx.ParamTags(``, `name:"v1ServerMux"`), fx.ResultTags(`name:"serverMux"`)),
			fx.Annotate(router.NewV1RoutesMux, fx.ResultTags(`name:"v1ServerMux"`)),
		),
		fx.Invoke(func(*http.Server) {}),
	).Run()
}