Combine two Streams into one StreamProvider

So this seems to work fine:

StreamProvider<User>.value(  value: auth.onAuthStateChanged.transform(    FlatMapStreamTransformer<FirebaseUser, User>(      (firebaseUser) => userService.streamUser(firebaseUser.uid),    ),  ),),

If anybody has doubts about this in certain edge cases, please let me know.

Thanks to pskink for the hint about flatMap.

Maybe you can try this approach:

main.dart

void main() => runApp(MyApp());class MyApp extends StatelessWidget {  @override  Widget build(BuildContext context) {    return MultiProvider(      providers: [        Provider<FirebaseUser>(          builder: (_) => FirebaseUser(),        ),      ],      child: AuthWidgetBuilder(builder: (context, userSnapshot) {        return MaterialApp(          theme: ThemeData(primarySwatch: Colors.indigo),          home: AuthWidget(userSnapshot: userSnapshot),        );      }),    );  }}

AuthWidgetBuilder.dart

Used to create user-dependant objects that need to be accessible by all widgets. This widget should live above the [MaterialApp]. See [AuthWidget], a descendant widget that consumes the snapshot generated by this builder.

class AuthWidgetBuilder extends StatelessWidget {  const AuthWidgetBuilder({Key key, @required this.builder}) : super(key: key);  final Widget Function(BuildContext, AsyncSnapshot<User>) builder;  @override  Widget build(BuildContext context) {    final authService =        Provider.of<FirebaseUser>(context, listen: false);    return StreamBuilder<User>(      stream: authService.onAuthStateChanged,      builder: (context, snapshot) {        final User user = snapshot.data;        if (user != null) {          return MultiProvider(            providers: [              Provider<User>.value(value: user),              Provider<UserService>(                builder: (_) => UserService(uid: user.uid),              ),            ],            child: builder(context, snapshot),          );        }        return builder(context, snapshot);      },    );  }}

AuthWidget.dart

Builds the signed-in or non signed-in UI, depending on the user snapshot. This widget should be below the [MaterialApp]. An [AuthWidgetBuilder] ancestor is required for this widget to work.

class AuthWidget extends StatelessWidget {  const AuthWidget({Key key, @required this.userSnapshot}) : super(key: key);  final AsyncSnapshot<User> userSnapshot;  @override  Widget build(BuildContext context) {    if (userSnapshot.connectionState == ConnectionState.active) {      return userSnapshot.hasData ? HomePage() : SignInPage();    }    return Scaffold(      body: Center(        child: CircularProgressIndicator(),      ),    );  }}

This is originally from the tutorial of advance provider from Andrea Bizotto.But I tailored some the code according to your your code above.Hope this works, good luck!

Reference: https://www.youtube.com/watch?v=B0QX2woHxaU&list=PLNnAcB93JKV-IarNvMKJv85nmr5nyZis8&index=5