Lack of NonNull anotations in factory methods

[MikolajKakol]

I was wondering if there shouldn't be an @javax.annotation.Nonnull it methods like:
Single.just
Observable.just
Observable.fromX
etc?

It would improve code quality on client side, since IDE might help detect early and compiler would print warning.

[akarnokd]

JSR 305 where that annotation lives is incompatible with Java 9 modules so we use our own annotations. Most ide will let you define RxJava's annotations as custom nullability annotations or are supported out of box.

PR welcome.

[MikolajKakol]

True, there are RxJava custom annotations and I see that most value for clients rely in io.reactivex.functions package. In order to make great improvements we should change
R apply(@NonNull T t) throws Exception;
to
@NonNull R apply(@NonNull T t) throws Exception;

Do you think that this is allowed?

[akarnokd]

The functions are a special case because some usages could work with nulls and they just create warnings. This has been discussed before:

https://github.com/ReactiveX/RxJava/issues?utf8=%E2%9C%93&q=is%3Aissue+nullable+is%3Aclosed+annotation

[freakomonk]

Hi. Can I take this up?

[akarnokd]

@freakomonk Fine by me. Nobody else seems to be working on this at the moment.

[freakomonk]

Sure @akarnokd . Any pointers to know before I start this up?

[akarnokd]

Beyond this issue, nothing specifically. We'll review the PR anyway and give you feedback if something needs changing.