Scalafix rules for cats

How to use

1. Install the Scalafix sbt plugin

2. Run the rules appropriate to your Cats version (see below)

Migration to Cats v2.2.0

First configure the SemanticDB compiler plugin to enable synthetics:

ThisBuild / scalacOptions += "-P:semanticdb:synthetics:on"

Then run Scalafix:

sbt scalafixAll github:typelevel/cats/Cats_v2_2_0

Available rules

• Type class instances are now available in implicit scope, so there is a rule to remove imports that are no longer needed

Migration to Cats v1.0.0

sbt scalafixAll github:typelevel/cats/Cats_v1_0_0

Available rules

• All Unapply enabled methods, e.g. sequenceU, traverseU, etc. are removed. Unapply enabled syntax ops are also removed. Please use the partial unification SI-2712 fix instead. The easiest way might be this sbt-plugin.

• The creation methods (left, right, apply, pure, etc.) in EitherT were improved to take less type arguments.

• EitherT.liftT was renamed to EitherT.liftF

• the lift method on WriterT, StateT, RWST and Kleisli was renamed to liftF

• CartesianBuilder (i.e. |@|) syntax is deprecated, use the apply syntax on tuples instead. E.g. (x |@| y |@| z).map(...) should be replaced by (x, y, z).mapN(...)

• Free.suspend is renamed to Free.defer for consistency.

• traverse1_, intercalate1 and sequence1_ in Reducible were renamed to nonEmptyTraverse_, nonEmptyIntercalate and nonEmptySequence_ respectively.

• cats.free.Inject is moved from cats-free to cats-core and renamed to cats.InjectK; cats.data.Prod is renamed to cats.data.Tuple2K; cats.data.Coproduct is renamed to cats.data.EitherK

• Apply syntax on tuple (e.g. (x, y, z).map3(...)) was moved from cats.syntax.tuple._ to cats.syntax.apply._ and renamed to mapN, contramapN and imapN respectively.

• Apply methods forEffect and followedBy were renamed to productL and productR respectively. This also effects forEffectEval, followedByEval, forEffectPar, and followedByPar.

• Split is removed, and the method split is moved to Arrow. Note that only under CommutativeArrow does it guarantee the non-interference between the effects. see #1567

WIP

• cats no longer publishes the all-inclusive bundle package "org.typelevel" % "cats", use cats-core, cats-free, or cats-law accordingly instead. If you need cats.free, use "org.typelevel" % "cats-free", if you need cats-laws use "org.typelevel" % "cats-laws", if neither, use "org.typelevel" % "cats-core".

• FunctorFilter, MonadCombine, MonadFilter, MonadReader, MonadState, MonadTrans, MonadWriter and TraverseFilter are no longer in cats, the functionalities they provided are inhereted by the new cats-mtl project. Please check here for migration guide.

• Several cats-core type class instances for cats.kernel were moved from their companion objects to separate traits and thus require imports from cats.instances.xxx._ (or the recommended import cats.implicits._) now. See #1659 for more details.

• foldLeftM is removed from Free, use foldM on Foldable instead, see #1117 for detail.

• iteratorFoldM was removed from Foldable due to #1716

To test the Scalafix rules

cd scalafix
sbt test