Cats v2.10.0 is a binary-compatible release in the 2.x series. It is published for Scala 2.12, 2.13, and 3.3+ with Scala.js 1.13+ and Scala Native 0.4.

This release includes #4477 which fixes the encoding of Apply (and Semigroupal) syntax to avoid allocating an intermediate "Ops" wrapper class. This affected commonly-used operators such as *>. Unfortunately libraries will need to re-compile and re-publish against Cats v2.10.0 to use the new allocation-free syntax.

Thanks to all the contributors to this release! There are many accumulated changes.

What's Changed

Features

• Add OptionT combinators for effectful Boolean by @ivan-klass in #4390
• Add Bifunctor#leftLiftTo by @eugkhp in #4336
• Add Kleisli.localK FunctionK helper by @ivan-klass in #4406
• add zip for NonEmptySeq by @CristinaHG in #4431
• Add Functor#composeBifunctor by @bpholt, @armanbilge in #4434
• Add Validated.unit by @VladKopanev in #4420
• Add raiseWhen/raiseUnless convenience methods to EitherObjectOps by @Daenyth in #4436
• OneAnd: add PartialOrder and Order instances by @satorg in #4460
• Add Defer instances for Eq, Hash, Order, Show, and variants by @morgen-peschke in #4414
• Fix ambiguous Const instances and add missing instances by @joroKr21 in #4458

Optimizations

• Avoid allocating an Option in NonEmptyList#last by @valencik in #4417
• Improve foldRight for Seq instance by @rudolmi in #4440

Fixes

• Move catsTraverseForSeq to lower-priority implicit scope by @UlisesTorrella in #4373
• Making Map.unorderedTraverse stack safe by @TonioGela in #4463
• Fix unnecessary syntax allocation by @mox692 in #4477

Documentation

• Nomenclature for the SemigroupK hierarchy by @TimWSpence in #4329
• Fix readme by @danicheg in #4368
• Fix the nested unordered list HTML view of docs/typeclasses/alternative.md by @ShapelessCat in #4371
• Fix typo by @Masynchin in #4381
• Add missing syntax highlightning by @Masynchin in #4382
• Add a link about fs2-throttler by @kovstas in #4359
• Publish alleycats docs on website by @armanbilge in #4393
• cats.implicits._ -> cats.syntax.all._ by @armanbilge in #4394
• Update no script links in readme by @RawToast in #4397
• Update CONTRIBUTING.md microsite information by @fabianhjr in #4399
• Improve Chain Documentation by @reardonj in #4386
• Add API documentation links by @reardonj in #4401
• f >>> g in symbols table by @jose-puente in #4411
• Fix outdated edit link in algebra docs by @lenguyenthanh in #4418
• Update version in readme by @lenguyenthanh in #4422
• Fix typo in Ior docs by @fighur in #4423
• Update Ring-like table in Algebra for Semifield added in #3979 by @benhutchison in #4426
• Add foldr note to Foldable doc by @lenguyenthanh in #4425
• Bump versions in law testing doc by @lenguyenthanh in #4424
• ExhaustiveCheck is a list, not a stream by @rossabaker in #4442
• Fix traverseWithIndex => traverseWithIndexM by @lenguyenthanh in #4443
• Fix typo in core's package object docs by @fatalem0 in #4446
• Fix jump_start_guide.md typo by @BokChoyWarrior in #4465
• Remove Either documentation page by @reardonj in #4400
• Add doctest for IdT by @bulatkhabib in #4445
• Fix typo by @bwignall in #4482

Adopters

• Add IPONWEB as an adopter by @bio-aeon in #4384
• Update ADOPTERS.md by @ehsun7b in #4435
• Add PITS Globale Datenrettungsdienste as an adopter by @arnoldberlin in #4472

Behind-the-scenes

• Bump base version to 2.10 by @armanbilge in #4341
• Remove plugins we get via sbt-typelevel by @armanbilge in #4344
• Clean up benchmarks' dependencies by @danicheg in #4355
• Fix Native CI by @armanbilge in #4363
• remove unused version number by @kailuowang in #4358
• Move NonEmptyReducible into its own file by @fabianhjr in #4398
• Delete PR template by @joroKr21 in #4459
• Replaced traverse benchmarks with something more representative by @djspiewak in #4403
• Update to sbt-typelevel 0.5.0 by @armanbilge in #4478

Updates

• Update scala3-library, ... to 3.3.0 by @typelevel-steward in #4448
• Update nscplugin, sbt-scala-native, ... to 0.4.14 by @typelevel-steward in #4454
• Update scala-library, scala-reflect to 2.12.18 by @typelevel-steward in #4455
• Update scala-library, scala-reflect to 2.13.11 by @typelevel-steward in #4456
• Update sbt-scalajs, scalajs-compiler, ... to 1.13.2 by @typelevel-steward in #4464

New Contributors

• @ShapelessCat made their first contribution in #4371
• @UlisesTorrella made their first contribution in #4373
• @Masynchin made their first contribution in #4381
• @bio-aeon made their first contribution in #4384
• @kovstas made their first contribution in #4359
• @fabianhjr made their first contribution in #4398
• @reardonj made their first contribution in #4386
• @eugkhp made their first contribution in #4336
• @jose-puente made their first contribution in #4411
• @lenguyenthanh made their first contribution in #4418
• @fighur made their first contribution in #4423
• @ehsun7b made their first contribution in #4435
• @CristinaHG made their first contribution in #4431
• @VladKopanev made their first contribution in #4420
• @rudolmi made their first contribution in #4440
• @fatalem0 made their first contribution in #4446
• @BokChoyWarrior made their first contribution in #4465
• @arnoldberlin made their first contribution in #4472
• @bulatkhabib made their first contribution in #4445
• @mox692 made their first contribution in #4477

Full Changelog: v2.9.0...v2.10.0