Version 3.0.0-RC3 (June 16, 2019)

This release depends on Cats-Effect 1.3.1 and Cats 1.6.1.

The next planned release will target Cats-Effect 2.0.0 with Scala 2.13 support.

NOTE: this release IS NOT binary compatible with 3.0.0-RC2, as it contains some API changes, but it should be source compatible (with @deprecated symbols where the case).

Sub-project: monix-execution

This sub-project no longer depends on cats-effect and there are various
improvement to Local aimed at fixing interop with Future. Note that
you might have to call Local.isolate to disable any sharing between tasks.

• PR #775: Simplified FutureUtils materialize & dematerialize

• PR #790: improve fixed rate scheduling on JS

• PR #803: Eagerly null out dequeued elements in ChunkedArrayQueue

• PR #822: remove dependency on cats-effect from monix-execution

• PR #773: change Cancelable.empty type to Cancelable

• PR #887: Shared locals with binds

• PR #888: Fix uncaught exception reporting for Scheduler

Sub-project: monix-catnap

• PR #778: Adds ConcurrentChannel

• PR #784: More concurrent tests for MVar/Semaphore

• PR #865: Adding FunctionK values for Task, Coeval

Sub-project: monix-eval

• PR #802: encapsulate local ctx on task execution

• PR #807: Improve encapsulation test, encapsulate locals on ContextShift

• PR #838: Add taskified variants of timeout combinators

• PR #839: TaskLocal should propagate when used with Bracket Methods

• PR #849: Specify exception on timeout

• PR #887: Shared locals with binds

• PR #865: Adding FunctionK values for Task, Coeval

Sub-project: monix-reactive

• PR #759: Add Contravariant Observer and Subscriber

• PR #760: add Observable.filterEval

• PR #774: Add FunctorFilter instances for Iterant&Observable

• PR #779: fork blocking i/o observable ops

• PR #794: Acquire lock per subscription instead of observable-wide lock

• PR #801: Observable buffers refactoring

• PR #819: Extend ObservableLike with filterNot method

• PR #831: SerializableSuite to no longer test Future for serializability

• PR #834: Observable.reduce should emit for single item source

• PR #846: Ensure mapParallelOrdered runs in parallel

• PR #872: Add observable take while inclusive

• PR #895: Fix memory leak in MapParallelOrderedObservable

Sub-project: monix-tail

• PR #778: Adds Iterant.channel, Iterant#consume

• PR #826: add Iterant.uncons operation

Chores

• PR #766: Update sbt-unidoc to 0.4.2

• PR #766: Update sbt-pgp to 1.1.2

• PR #768: Update sbt-mima-plugin to 0.3.0

• PR #769: Update sbt-git to 1.0.0

• PR #770: Update jctools-core to 2.1.2

• PR #771: Update kind-projector to 0.9.8

• PR #772: Update sbt-jmh to 0.3.4

• PR #771: Update kind-projector to 0.9.9

• PR #783: Use globally accessible (rather than local) source paths in JS source maps (#781)

• PR #785: Update sbt-scalajs, scalajs-compiler, scalajs-library... to 0.6.26

• PR #788: Update cats-effect, cats-effect-laws to 1.1.0

• PR #796: fix scalacOptions

• PR #797: Scala 2.12.8

• PR #798: Update intervalWithFixedDelay scaladoc

• PR #805: Rename keysBuffer to os in groupBy's parameters

• PR #808: Update Copyright to 2019

• PR #810: sbt 1.2.8 (was 1.1.0)

• PR #812: Update Minitest to 2.3.2

• PR #813: Disable code coverage

• PR #818: Update Cats-Effect to 1.2.0

• PR #820: Update cats-laws to 1.5.0

• PR #821: Update cats-laws to 1.6.0

• PR #823: Scala 2.13 support

• PR #821: Update sbt-header to 5.1.0

• PR #827: Remove comments from .jvmopts

• PR #833: Fix build for 2.13.0-M5 by deactivating Mima for it

• PR #840: Add adopters list seed

• PR #842: Fixed deprecation docs for Task#coeval

• PR #843: Remove dead code from tests

• PR #844: Update sbt-header to 5.2.0

• PR #847: Update ExecutionModel.scala

• PR #850: Increase rate in AsyncSchedulerSuite

• PR #854: fix apparently erronous code involving Unit companion

• PR #855: Update sbt-jmh to 0.3.5

• PR #857: Make benchmarks compile

• PR #859: Update sbt-scalajs, scalajs-compiler to 0.6.27

• PR #867: Update kind-projector to 0.10.0

• PR #869: fix compile errors with latest Scala 2.13

• PR #874: Update cats-effect, cats-effect-laws to 1.3.0

• PR #878: Compile Benchmarks in CI

• PR #879: Do on subscription cancel scaladoc fix

• PR #889: Update cats-effect, cats-effect-laws to 1.3.1

• PR #894: Add UnsafeBecauseImpure Annotation to foreach.

• PR #896: Update cats-laws to 1.6.1

• PR #898: Reformating via Scalafmt

• PR #899: Fix autoCancelableRunLoops comment.

• PR #901: avoid deprecated unicode arrow chars

• PR #902: reformat build files

Thanks

People that made this release possible, in alphabetical order:

• Alexandru Nedelcu (@alexandru)
• Allan Timothy Leong (@allantl)
• Daniel Neades (@djneades)
• Dawid Dworak (@ddworak)
• Eugene Platonov (@jozic)
• Itamar Ravid (@iravid)
• Jorge (@jvican)
• Jorge Branco (@jorgedfbranco)
• Kenji Yoshida (@xuwei-k)
• Luke Stephenson (@lukestephenson)
• Matthew de Detrich (@mdedetrich)
• Mikhail Chugunkov (@poslegm)
• Oleg Pyzhcov (@oleg-py)
• Ota Hauptmann (@Otah)
• Piotr Gawryś (@Avasil)
• Roman Tkalenko (@tkroman)
• Ryo Fukumuro (@rfkm)
• Sam Guymer (@guymers)
• Seth Tisue (@SethTisue)
• Tanaka Takaya (@takayahilton)
• Yann Simon (@yanns)

And special thanks to our top contributor in this release:
https://github.com/fthomas/scala-steward :)

Final milestone release before the RC and the final and stable 3.0.0.

Highlights

Local and TaskLocal

Special thanks to Leandro Bolivar for implementing propagation of "local vars" (aka Local and TaskLocal, the equivalents of ThreadLocal, but for usage with Future and Task). The inspiration was com.twitter.util.Local and scala.util.DynamicVariable.

Right now the Monix Task is the only (known) IO data type for Scala that can work with such locals and because of the provided TracingScheduler, you can work with Scala's Future too.

See:

• original request
• pull request

Pure cancellation, .start, .uncanceled, race

This release also lands a long awaited feature for Task — pure cancellation, aka Task.cancel. It's building on top of the current Task implementation, however it changes the API — e.g. in order to keep Task pure, the chooseFirstOf operator is now gone, being replaced with an equivalent racePair that operates with tasks and pure functions.

See:

• pull request

Performance optimizations

One other highlight of the release are the performance improvements for Task and Coeval, an on-going process to make sure that Monix's Task remains the best implementation in Scala's ecosystem.

See:

• original issue
• pull request: first batch
• pull request: second batch

Typelevel Cats

We now depend on Cats 1.0.1 and cats-effect 0.8.

This unblocks the 3.0.0 release, because Cats 1.x has stronger backwards compatibility guarantees.

Pull requests

• PR #464: updates dependencies, Scala to 2.12.4 and 2.11.12, JCTools to 2.1.1, Minitest to 2.0.0, Scala.js to 0.6.21
• PR #462: Fix for timeoutTo to cancel source task directly after timeout
• PR #444: Add localContextPropagation to Task.Options, implement tracing Local vars
• PR 470: increase test coverage
• PR #473: Fix issue where fromAsyncStateAction is not safe for user code
• PR #485 and PR #489: Updates Cats to 1.0.1 and cats-effect to 0.8
• PR #474: Task / Coeval Run-loop Optimizations, First Batch
• PR #492: Second batch of optimizations
• PR #494: Task.cancel as a pure action, along with .start, .race and .uncancelable

Release is binary backwards compatible with series 2.3.x.

Bug fixes:

• Issue #468:
  Observables created using concat don't get canceled
  (critical)
• Issue #483:
  stack overflow error on MVar.put
• Issue #541:
  observable.take(0) shouldn't subscribe to the source at all
• Issue #475:
  Observable.fromAsyncStateAction does not protect against
  exceptions thrown in use code

Issue #468 in particular is pretty serious as it can lead to
resource leaks. Read the pull request
for more details.

Upgrade to 2.3.3 is recommended!

This release upgrades Cats to 1.0-RC1 and cats-effect to 0.5.

This involved changes to the exposed instances:

1. the non-deterministic instance (e.g. import Task.nondeterminism) is gone
2. integrated cats.Parallel instead, a new type class that's exposing an alternative Applicative that doesn't do ordering in ap and map2
3. Iterant now exposes parZip and parZipMap for doing zips in parallel, based on cats.Parallel

Enjoy!

This is a major release that breaks both binary and source compatibility. The major themes of this release:

1. deep integration with Typelevel Cats
2. the Iterant data type for lawful pull-based streaming, in a new monix-tail sub-project
3. API refactoring, eliminated deprecations
4. major improvements to Observable, Task, Coeval and CancelableFuture

Typelevel Cats integration:

• PR #370: introduced Cats and cats-effect as direct dependencies
• PR #377: added Cats related conversions, along with naming changes for consistency (e.g. renamed Coeval.Attempt to Coeval.Eager)
• PR #387: updated Cats to 1.0.0-MF, removed deprecated functions and classes
• PR #397: standardizes on Cats-related naming, removes Coeval's Comonad implementation
• PR #398: re-adds instances for CoflatMap
• PR #427: adds conversions from Cats to Observable

New monix-tail sub-project, exposing monix.tail.Iterant[F[_], A]:

• PR #280: introduces Iterant[F[_], A] for pull-based streaming based on Task / Coeval
• PR #396: adds the Iterant.scan operator
• PR #403: adds Iterant.foldWhileLeftL and Iterant.foldWhileLeftEvalL operators
• PR #404: adds Iterant existsL, forallL, changes Observable.foldWhileL (breaking change)
• PR #402: adds Iterant.foldRightL operator
• PR #405: adds Iterant ops - findL, foldL, maxL, minL, reduceL
• PR #407: adds Iterant ops - countL, distinctUntilChanged, distinctUntilChangedByKey
• PR #412: adds scanEval on both Iterant and Observable
• PR #411: another naming consistency change between Observable and Iterant
• PR #413: Iterant.bufferSliding, bufferTumbling and batched operators
• PR #417 and PR #418: Reactive Streams implementation for Iterant

Improvements for monix-execution and CancelableFuture:

• PR #390: changes for flatMap on CancelableFuture to cancel all involved futures (thanks to @larsrh)
• PR #395: adds Cats type class implementations for CancelableFuture
• PR #431: improvements to CancelableFuture to get rid of memory leak, also adding utils like CancelableFuture.async
• PR #432: further fixes to CancelableFuture, since describing a cancellable flatMap is a hard problem
• PR #418: adds flip convenience method to AtomicBoolean (thanks to @Wogan)

Improvements for monix-reactive and Observable:

• PR #391: makes Observable concatenation (++) stack safe
• PR #408: changes for Iterant and Cats consistency (make use of Eq and Order type classes, add foldF and foldL, remove distinct and distinctByKey)
• PR #368: added the Observable.intersperse operator (thanks to @omainegra)
• PR #384: added contramap method to Callback (thanks to @Wogan)
• PR #425: gets rid of ObservableLike, makes Observable an abstract class where the operators are final, Pipe no longer has Observable's operators, just transform

Improvements for monix-eval, Task and Coeval:

• PR #410: Task and Coeval performance optimisations
• PR #422: adds Task.shift, an innovation inspired by cats.effect.IO
• PR #424: Task refactoring, gets rid of Task.OnFinish type alias
• PR #430: Coeval and Task refactoring to the run methods for consistency, introduced map2, map3...map6 on both Task and Coeval, renamed zipMap* to parMap2, parMap3... parMap6 for Task

Administrative and build changes:

• PR #372: configured project for Git hash versioning (for enabling automatic releases)
• PR #378: dropped Scala 2.10 support - enabled automatic deployments through Travis-ci, wrote a blog post documenting the necessarily steps, see Automatic Releases to Maven Central with Travis and SBT
• PR #423: updates Scala.js to 0.6.20, the final in the series before 1.0.0