typelevel/cats-effect v3.7.0 on GitHub

This is the fifty-ninth release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with the 3.7.x lineage.

What's Changed

This is a relatively smaller minor release jump relative to 3.6.x since it contains a major and long-anticipated enhancement: support for Scala Native 0.5, including full multithreading on LLVM! This has been a very long time coming, and we've been planning how to provide this support and planting the seeds for several years now. As noted in previous release notes, the integrated runtime released in 3.6.0 provides the basic building blocks for true, practically usable multithreaded asynchronous I/O on LLVM, and this release finally brings all of those pieces to fruition.

Full support has been implemented for epoll and kqueue, and we intend to extend this support to io_uring in the future. These polling systems have been significantly upgraded and enhanced since 3.6.x in order to support the same sort of thread coordination that has been present on the JVM from the beginning.

Of course, the largest piece of this is the WorkStealingThreadPool itself. This was ported from JVM-only to cross-build entirely on both JVM and LLVM targets. Surprisingly, almost no changes were required to make this possible! It is a testament to the thought and effort which went into Scala Native 0.5 that this port was dramatically smoother and less complex than anyone could have reasonably predicted. While we did run into a few minor issues with Scala Native, only one major problem with its multithreading support was encountered, and it only applies in a very niche scenario which was easily worked around.

We really cannot stress enough how impressed we are with Scala Center and Virtus' work on this front. Scala Native 0.5 is quite the triumph, and Cats Effect 3.7 is the proof. Going forward, you should essentially expect rough parity between scheduling functionality on JVM and LLVM, with JavaScript now being the unusual one (due to its single-threaded nature).

As an aside, it's worth noting that this parity holds despite the fact that Scala Native actually implements subtly different memory publication semantics than the JVM in some very specific circumstances. The Cats Effect concurrency state model (i.e. Ref/Deferred) is such that these semantic differences are entirely invisible in userspace, while the performance benefits are present regardless. This is one example of the careful planning and coordination which went into this release spanning across many people and multiple projects.

The one area in which Cats Effect on Scala Native meaningfully lags behind the JVM is fiber tracing. This functionality should exist on LLVM, but it appears that the APIs do not work correctly at runtime. It is expected that these bugs will be resolved in a future Scala Native release, at which point we'll be able to enable the functionality in Cats Effect.

Enhancements

Add SecureRandom instance to SyncIO companion by @qxrein in #4324
Add realTimeZonedDateTime to Clock JVM extensions by @mmienko in #4316
Add support for Native multithreaded execution by @durban in #4201
blocking and interruptible on Scala Native by @djspiewak in #4378
Add IOLocal#asLocal[F[_]]:Local[F,A] by @NthPortal in #4438
Add awaitEvent to expose the full featureset of kqueue by @rahulrangers in #4423
Add IORuntime#liveFiberSnapshot by @iRevive in #4444
Add a TestConsole by @morgen-peschke in #4394
Add NonEmptyHotswap by @morgen-peschke in #4267
Add KeyedMutex by @BalmungSan in #4065
Implement PollerMetrics for EpollSystem by @antoniojimeneznieto in #4335
Implement PollerMetrics for KqueueSystem by @antoniojimeneznieto in #4336
Add AtomicMap by @BalmungSan in #4424
Sync SyncIO.realTime* methods with Clock implementation by @satorg in #4522
Add derivation of LiftIO from LiftValue by @NthPortal in #4481
SecureRandom.javaSecuritySecureRandom for two effect types by @dpevunov-cp in #4338
Add Lift{Value,Kind} instances for Resource by @NthPortal in #4478

Bug Fixes

Don't expose private WSTP type in method signature by @armanbilge in #4290
Fix wstp shutdown interrupt (3.x edition) by @djspiewak in #4344
Make IOFiber#{_join,_cancel} volatile on Native by @durban in #4400
Removed IORuntimeBuilder#addPoller on Scala.js by @djspiewak in #4419
Use _exit instead of System.exit in fatal cases by @djspiewak in #4428
Make the heap in TimerHeap volatile on native by @armanbilge in #4443

Documentation

docs: provide an example on how to collect fiber dump programmatically by @iRevive in #4399
code snippet typo in faq.md by @combinatorist in #4395
Fix typo in documentation of function tryOfferN of QueueSink and PQueueSink. by @nmichael44 in #4384
Change tutorial CopyFile object name by @davidsalter in #4458
Fix identity in Ref documentation by @reardonj in #4466
Clarify how MapRef can be total by @mtomko in #4475
Update weaver-test organization in docs by @zainab-ali in #4499
Tweak fiber names in IOLocal doc by @japgolly in #4551

Behind the Scenes

Update scalafmt-core to 3.8.4 in series/3.x by @typelevel-steward[bot] in #4235
Update sbt-scalafix to 0.14.0 in series/3.x by @typelevel-steward[bot] in #4237
Update sbt-typelevel to 0.7.6 in series/3.x by @typelevel-steward[bot] in #4243
Update scalafmt-core to 3.8.5 in series/3.x by @typelevel-steward[bot] in #4242
Update scala-library to 2.13.16 in series/3.x by @typelevel-steward[bot] in #4239
Update scalafmt-core to 3.8.6 in series/3.x by @typelevel-steward[bot] in #4251
Update sbt-scalajs, scalajs-compiler, ... to 1.18.2 in series/3.x by @typelevel-steward[bot] in #4249
Update sbt-typelevel to 0.7.7 in series/3.x by @typelevel-steward[bot] in #4252
Revert documentation format changes by @mzuehlke in #4246
flake.lock: Update by @typelevel-steward[bot] in #4258
Update scala3-library, ... to 3.3.5 in series/3.x by @typelevel-steward[bot] in #4261
Update sbt-mdoc to 2.6.3 in series/3.x by @typelevel-steward[bot] in #4265
Update scalafmt-core to 3.9.1 in series/3.x by @typelevel-steward[bot] in #4278
Update sbt-scalafix to 0.14.2 in series/3.x by @typelevel-steward[bot] in #4275
Update sbt-mdoc to 2.6.4 in series/3.x by @typelevel-steward[bot] in #4272
flake.lock: Update by @typelevel-steward[bot] in #4281
Backport v3.6.0-RC2 changes by @djspiewak in #4282
Replace specs2 with munit by @iRevive in #4216
Update scalafmt-core to 3.9.2 in series/3.x by @typelevel-steward[bot] in #4284
Update sbt, scripted-plugin to 1.10.8 in series/3.x by @typelevel-steward[bot] in #4285
Update sbt, scripted-plugin to 1.10.9 in series/3.x by @typelevel-steward[bot] in #4286
Update sbt, scripted-plugin to 1.10.10 in series/3.x by @typelevel-steward[bot] in #4288
Update scalafmt-core to 3.9.3 in series/3.x by @typelevel-steward[bot] in #4294
Update scalafmt-core to 3.9.4 in series/3.x by @typelevel-steward[bot] in #4297
Update sbt-mdoc to 2.6.5 in series/3.x by @typelevel-steward[bot] in #4304
Update sbt, scripted-plugin to 1.10.11 in series/3.x by @typelevel-steward[bot] in #4303
Merge changes from 3.6.0 into series/3.x by @djspiewak in #4312
fix: Nix development Enviroment & Readme Fix by @qxrein in #4298
Replace deprecated commands in build.sbt by @iRevive in #4339
Update cats-core, cats-free, ... to 2.13.0 in series/3.x by @typelevel-steward[bot] in #4356
Merge changes from 3.6.1 into series/3.x by @armanbilge in #4364
Update sbt-scalafix to 0.14.3 in series/3.x by @typelevel-steward[bot] in #4403
flake.lock: Update by @typelevel-steward[bot] in #4327
Update sbt, scripted-plugin to 1.11.0 in series/3.x by @typelevel-steward[bot] in #4413
Update sbt, scripted-plugin to 1.11.1 in series/3.x by @typelevel-steward[bot] in #4416
Update sbt-typelevel to 0.8.0 in series/3.x by @typelevel-steward[bot] in #4417
Update sbt, scripted-plugin to 1.11.2 in series/3.x by @typelevel-steward[bot] in #4420
Update sbt, scripted-plugin to 1.11.3 in series/3.x by @typelevel-steward[bot] in #4427
flake.lock: Update by @typelevel-steward[bot] in #4414
Merge changes from 3.6.2 into series/3.x by @djspiewak in #4436
Update versions for 3.6.3 by @djspiewak in #4452
Merge changes from 3.6.3 into series/3.x by @djspiewak in #4453
Update sbt-mdoc to 2.7.2 in series/3.x by @typelevel-steward[bot] in #4441
Backport more recent changes from series/3.6.x by @djspiewak in #4459
flake.lock: Update by @typelevel-steward[bot] in #4461
Update sbt, scripted-plugin to 1.11.4 in series/3.x by @typelevel-steward[bot] in #4467
Update cats-mtl, cats-mtl-laws to 1.6.0 in series/3.x by @typelevel-steward[bot] in #4472
Update sbt, scripted-plugin to 1.11.5 in series/3.x by @typelevel-steward[bot] in #4477
flake.lock: Update by @typelevel-steward[bot] in #4480
Update sbt, scripted-plugin to 1.11.6 in series/3.x by @typelevel-steward[bot] in #4485
Update scalacheck to 1.19.0 in series/3.x by @typelevel-steward[bot] in #4484
flake.lock: Update by @typelevel-steward[bot] in #4491
flake.lock: Update by @typelevel-steward[bot] in #4521
Update sbt, scripted-plugin to 1.11.7 in series/3.x by @typelevel-steward[bot] in #4496
scala-native 0.5.9 by @durban in #4510
scala 3.3.7 by @durban in #4519
Update scalafmt-core to 3.9.10 in series/3.x by @typelevel-steward[bot] in #4536
Update sbt-jmh to 0.4.8 in series/3.x by @typelevel-steward[bot] in #4492
Update sbt-typelevel to 0.8.4 in series/3.x by @typelevel-steward[bot] in #4533
flake.lock: Update by @typelevel-steward[bot] in #4537
Update auxlib, clib, javalib, nativelib, ... to 0.5.10 in series/3.x by @typelevel-steward[bot] in #4545
Update scalafmt-core to 3.10.4 in series/3.x by @typelevel-steward[bot] in #4544
flake.lock: Update by @typelevel-steward[bot] in #4547
flake.lock: Update by @typelevel-steward[bot] in #4558
Update sbt-typelevel to 0.8.5 in series/3.x by @typelevel-steward[bot] in #4555
Update scalafmt-core to 3.10.7 in series/3.x by @typelevel-steward[bot] in #4552
Upgrade all the things (take 3?) by @djspiewak in #4563
Update scala-library to 2.13.18 in series/3.x by @typelevel-steward[bot] in #4528
Update sbt-mdoc to 2.8.2 in series/3.x by @typelevel-steward[bot] in #4535
Update sbt-scalajs, scalajs-compiler, ... to 1.20.2 in series/3.x by @typelevel-steward[bot] in #4542
Update sbt-scalafix to 0.14.6 in series/3.x by @typelevel-steward[bot] in #4557
Update scala-library to 2.12.21 in series/3.x by @typelevel-steward[bot] in #4530
Update munit-scalacheck to 1.2.0 in series/3.x by @typelevel-steward[bot] in #4486
Update sbt, scripted-plugin to 1.12.5 in series/3.x by @typelevel-steward[bot] in #4559

Uncategorized

Revert "fix: Nix development Enviroment & Readme Fix" by @djspiewak in #4376
Fix source compatibility with Scala 3.6 by @mbovel in #4381
SN 0.5.6 -> 0.5.7 -> 0.5.8 by @durban in #4362

New Contributors

@mmienko made their first contribution in #4316
@mbovel made their first contribution in #4381
@combinatorist made their first contribution in #4395
@nmichael44 made their first contribution in #4384
@NthPortal made their first contribution in #4438
@morgen-peschke made their first contribution in #4394
@davidsalter made their first contribution in #4458
@reardonj made their first contribution in #4466
@zainab-ali made their first contribution in #4499
@dpevunov-cp made their first contribution in #4338
@japgolly made their first contribution in #4551

Full Changelog: v3.6.3...v3.7.0