is it a good idea to use // ignore: missing_return in an future fuction where we are using conditioning to return answer?

The warnings like this actually help you to write clean error-free code. Don't ever try to ignore them, Try to fix them by understanding it.

Your function getProfile() expecting a Future<UserModel> as its return type.

Yes, you are returning a UserModel on the else condition, but you are not returning anything from the function if the condition (_user == null) is true.

Based on your use case, you could do something like,

 Future<UserModel> getProfile() async {    if (_user == null) {      /// sets the _user if its null      _user = await Provider.of<UserProvider>(context).fetchUserProfile();    }     ///returns the _user    return _user;     }

No, that's bad. Someone told you there is a problem and instead of fixing the problem you told them to shut up. Your compiler won't take it personally, but it's still not a good move to write quality code.

You are missing a return. In other languages, this would be a compiler error, not a warning. Your code is flawed. You need to fix it.

You said your method returns a UserModel and if _user is null, it simple doesn't.

Since I don't know what you want to happen, I can only make suggestions. I guess you want this method to return the user and load it if it has not been loaded yet. So this would be your proper way of doing it:

Future<UserModel> getProfile() async {    if (_user == null) {      _user = await Provider.of<UserProvider>(context).fetchUserProfile();    }           return _user;}