3.0.0-RC2 release preparations

Version 3.0.0-RC2 - August 20, 2019 (Maven)

Javadocs

This is an early release for 3.0.0 to allow preparations for the breaking API changes and cleanups.

Please check out the wiki page What’s different in 3.0 from time to time for the details and migration guide.

Major change

After considering several factors, the components of RxJava 3 have been moved to a new base package to avoid class file conflicts due to having v2 and v3 in the same project. The new base package is io.reactivex.rxjava3 and the base types will live in io.reactivex.rxjava3.core:

Name	v2	v3
Base package	io.reactivex	io.reactivex.rxjava3
Flowable	io.reactivex.Flowable	io.reactivex.rxjava3.core.Flowable
PublishSubject	io.reactivex.subjects.PublishSubject	io.reactivex.rxjava3.subjects.PublishSubject
ConnectableObservable	io.reactivex.observables.ConnectableObservable	io.reactivex.rxjava3.observables.ConnectableObservable
Function	io.reactivex.functions.Function	io.reactivex.rxjava3.functions.Function
etc.

Flowables of the two versions can talk to each other without bridges because both implement the Reactive Streams’ interfaces such as Publisher:

io.reactivex.Flowable.range(1, 10)
    .flatMap(v -> io.reactivex.rxjava3.core.Flowable.just(v * 10))
    .subscribeWith(new io.reactivex.rxjava3.subscribers.TestSubscriber<>())
    .assertResult(10, 20, 30, 40, 50, 60, 70, 80, 90, 100);

The other reactive types do not share such base interfaces (they have their own respective copies) and will require bridges, likely provided via 3rd party libraries as with v1->v2 or v1->v3 bridges.

Dependency changes

• Upgrade to Reactive Streams 1.0.3-RC1 (#6621)

API changes

• Widen throws on the XOnSubscribe interfaces (#6579)

Behavior changes

• Constrain upstream requests of elementAt and first operators (#6620)

Bugfixes

• Fix switchMaps inconsistency swallowing errors when cancelled (#6572)
• Fix ObservableBlockingSubscribe compares TERMINATED with wrong object (#6577)
• Fix truncation bugs in replay() and ReplaySubject/Processor (#6582)
• Fix mergeWith not cancelling the other source if the main errors (#6598)
• Fix refCount not resetting when termination triggers cross-cancel (#6609)
• Fix many operators swallowing undeliverable exceptions (#6612)
• Fix switchMap incorrect sync-fusion & error management (#6616)

Documentation enhancements

No changes in this release.

Other

• Create a base test class and have all unit tests extend it (#6589, #6594, #6595, #6600, #6604, #6607)
• Refactor to io.reactivex.rxjava3.** (#6621)

[JakeWharton]

I would prefer 3.0 target Java 9 so it can use j.u.c.Flow directly instead of RS.

But,

There are no indications that android will use java8+

Aside from the platform shipping the APIs of Java 8 a few years ago, the language features have been supported by the toolchain for a long time and library desugaring of those shipped APIs so that they work on older platforms was announced to be coming this fall at I/O and it’s already available in custom D8/R8 builds.

[akarnokd]

December this year.