Fix zio#94, add catz.core object with implicits that require only cat…

…s-core, not cats-effect

- also update README.md

README.md

@@ -5,7 +5,7 @@
 
 This library provides instances required by Cats Effect.
 
-## `IO` Cats Effect's instances
+## `ZIO` Cats Effect instances
 
 **ZIO** integrates with Typelevel libraries by providing an instance of `ConcurrentEffect` for `IO` as required, for instance, by `fs2`, `doobie` and `http4s`. Actually, I lied a little bit, it is not possible to implement `ConcurrentEffect` for any error type since `ConcurrentEffect` extends `MonadError` of `Throwable`.
 
@@ -17,6 +17,22 @@ For convenience we have defined an alias as follow:
 
 Therefore, we provide an instance of `ConcurrentEffect[Task]`.
 
+## ConcurrentEffect
+
+In order to get a `ConcurrentEffect[Task]` or `ConcurrentEffect[RIO[R, *]]` we need an implicit `Runtime[R]` in scope. The easiest way to get it is using `ZIO.runtime`:
+
+```scala
+import cats.effect._
+import zio._
+import zio.interop.catz._
+
+def getCE = {
+  ZIO.runtime.map { implicit r: Runtime[Any] =>
+    val F: ConcurrentEffect[Task] = implicitly
+  }
+}
+```
+
 ### Timer
 
 In order to get a `cats.effect.Timer[Task]` instance we need an extra import:
@@ -27,6 +43,16 @@ import zio.interop.catz.implicits._
 
 The reason it is not provided by the default "interop" import is that it makes testing programs that require timing capabilities hard so an extra import wherever needed makes reasoning about it much easier.
 
+### cats-core
+
+If you only need instances for `cats-core` typeclasses, not `cats-effect` import `zio.interop.catz.core._`:
+
+````scala
+import zio.interop.catz.core._
+````
+
+Note that this library only has an `Optional` dependency on cats-effect – if you or your libraries don't depend on it, this library will not add it to the classpath.
+
 ### Example
 
 The following example shows how to use ZIO with Doobie (a library for JDBC access) and FS2 (a streaming library), which both rely on Cats Effect instances:

build.sbt

@@ -1,6 +1,6 @@
-import sbtcrossproject.CrossPlugin.autoImport.crossProject
-import explicitdeps.ExplicitDepsPlugin.autoImport.moduleFilterRemoveValue
 import BuildHelper._
+import explicitdeps.ExplicitDepsPlugin.autoImport.moduleFilterRemoveValue
+import sbtcrossproject.CrossPlugin.autoImport.crossProject
 
 name := "interop-cats"
 
@@ -72,3 +72,22 @@ lazy val interopCatsJS = interopCats.js
   .settings(
     libraryDependencies += "io.github.cquiroz" %%% "scala-java-time" % "2.0.0-RC3" % Test
   )
+
+lazy val coreOnlyTest = crossProject(JSPlatform, JVMPlatform)
+  .in(file("core-only-test"))
+  .dependsOn(interopCats)
+  .settings(stdSettings("core-only-test"))
+  .settings(skip in publish := true)
+  .settings(
+    libraryDependencies ++= Seq(
+      "org.typelevel" %%% "cats-core"    % "2.0.0"      % Test,
+      "dev.zio"       %%% "zio-test-sbt" % "1.0.0-RC15" % Test
+    )
+  )
+  .settings(testFrameworks += new TestFramework("zio.test.sbt.ZTestFramework"))
+
+lazy val coreOnlyTestJVM = coreOnlyTest.jvm
+lazy val coreOnlyTestJS = coreOnlyTest.js
+  .settings(
+    libraryDependencies += "io.github.cquiroz" %%% "scala-java-time" % "2.0.0-RC3" % Test
+  )

core-only-test/shared/src/test/scala/zio/interop/test/CoreSummonSpec.scala

@@ -0,0 +1,55 @@
+package zio.interop.test
+
+import cats.data.NonEmptyList
+import cats.{ Bifunctor, Monad, MonadError, SemigroupK }
+import zio._
+import zio.interop.catz.core._
+import zio.stream.interop.catz.core._
+import zio.stream.{ Stream, ZStream }
+import zio.test.Assertion._
+import zio.test.{ DefaultRunnableSpec, test, _ }
+
+object CoreSummonSpec
+    extends DefaultRunnableSpec(
+      suite("summons from catz.core work with only a cats-core dependency")(
+        test("ZIO instances") {
+          val monad      = implicitly[Monad[UIO]]
+          val monadError = implicitly[MonadError[Task, Throwable]]
+          val semigroupK = implicitly[SemigroupK[IO[NonEmptyList[Unit], ?]]]
+          val bifunctor  = implicitly[Bifunctor[IO]]
+
+          monad.map(ZIO.unit)(identity)
+          monadError.map(ZIO.unit)(identity)
+          semigroupK.combineK(ZIO.unit, ZIO.unit)
+          bifunctor.leftMap(ZIO.fromOption(None))(identity)
+
+          assert((), anything)
+        },
+        test("ZManaged instances") {
+          val monad      = implicitly[Monad[ZManaged[Any, Nothing, ?]]]
+          val monadError = implicitly[MonadError[Managed[Throwable, ?], Throwable]]
+          val semigroupK = implicitly[SemigroupK[Managed[Nothing, ?]]]
+          val bifunctor  = implicitly[Bifunctor[Managed]]
+
+          monad.map(ZManaged.unit)(identity)
+          monadError.map(ZManaged.unit)(identity)
+          semigroupK.combineK(ZManaged.unit, ZManaged.unit)
+          bifunctor.leftMap(ZManaged.fail(()))(identity)
+
+          assert((), anything)
+        },
+        test("ZStream instances") {
+          val monad      = implicitly[Monad[ZStream[Any, Nothing, ?]]]
+          val monadError = implicitly[MonadError[Stream[Throwable, ?], Throwable]]
+          val semigroupK = implicitly[SemigroupK[Stream[Nothing, ?]]]
+          val bifunctor  = implicitly[Bifunctor[Stream]]
+
+          monad.map(ZStream.unit)(identity)
+          monadError.map(ZStream.unit)(identity)
+          semigroupK.combineK(ZStream.unit, ZStream.unit)
+          bifunctor.leftMap(ZStream.fail(()))(identity)
+
+          assert((), anything)
+        }
+      )
+    )

interop-cats/shared/src/main/scala/zio/interop/cats.scala

@@ -26,12 +26,17 @@ import zio.clock.Clock
 import scala.concurrent.ExecutionContext
 import scala.concurrent.duration.{ FiniteDuration, NANOSECONDS, TimeUnit }
 
-object catz extends CatsPlatform {
+object catz extends CatsEffectPlatform {
+  object core extends CatsPlatform
   object mtl  extends CatsMtlPlatform
   object test extends CatsTestFunctions
 }
 
-abstract class CatsPlatform extends CatsInstances with CatsZManagedInstances with CatsZManagedSyntax {
+abstract class CatsEffectPlatform
+    extends CatsEffectInstances
+    with CatsEffectZManagedInstances
+    with CatsZManagedInstances
+    with CatsZManagedSyntax {
   val console: interop.console.cats.type = interop.console.cats
 
   trait CatsApp extends App {
@@ -55,7 +60,10 @@ abstract class CatsPlatform extends CatsInstances with CatsZManagedInstances wit
   }
 }
 
-abstract class CatsInstances extends CatsInstances1 {
+abstract class CatsPlatform extends CatsInstances with CatsZManagedInstances
+
+abstract class CatsEffectInstances extends CatsInstances with CatsEffectInstances1 {
+
   implicit def zioContextShift[R, E]: ContextShift[ZIO[R, E, *]] = new ContextShift[ZIO[R, E, *]] {
     override def shift: ZIO[R, E, Unit] =
       ZIO.yieldNow
@@ -80,6 +88,15 @@ abstract class CatsInstances extends CatsInstances1 {
   implicit def taskEffectInstance[R](implicit runtime: Runtime[R]): effect.ConcurrentEffect[RIO[R, *]] =
     new CatsConcurrentEffect[R](runtime)
 
+}
+
+sealed trait CatsEffectInstances1 {
+  implicit def taskConcurrentInstance[R]: effect.Concurrent[RIO[R, *]] =
+    new CatsConcurrent[R]
+}
+
+abstract class CatsInstances extends CatsInstances1 {
+
   implicit def monoidKInstance[R, E: Monoid]: MonoidK[ZIO[R, E, *]] =
     new CatsMonoidK[R, E]
 
@@ -91,9 +108,6 @@ abstract class CatsInstances extends CatsInstances1 {
 
 sealed abstract class CatsInstances1 extends CatsInstances2 {
 
-  implicit def taskConcurrentInstance[R]: effect.Concurrent[RIO[R, *]] =
-    new CatsConcurrent[R]
-
   implicit def parallelInstance[R, E]: Parallel.Aux[ZIO[R, E, *], ParIO[R, E, *]] =
     new CatsParallel[R, E](monadErrorInstance)
 

interop-cats/shared/src/main/scala/zio/interop/catszmanaged.scala

@@ -80,6 +80,18 @@ final class ZManagedSyntax[R, E, A](private val managed: ZManaged[R, E, A]) exte
 
 }
 
+trait CatsEffectZManagedInstances {
+
+  implicit def liftIOZManagedInstances[R](
+    implicit ev: LiftIO[ZIO[R, Throwable, ?]]
+  ): LiftIO[ZManaged[R, Throwable, ?]] =
+    new LiftIO[ZManaged[R, Throwable, ?]] {
+      override def liftIO[A](ioa: CIO[A]): ZManaged[R, Throwable, A] =
+        ZManaged.fromEffect(ev.liftIO(ioa))
+    }
+
+}
+
 trait CatsZManagedInstances extends CatsZManagedInstances1 {
 
   implicit def monadErrorZManagedInstances[R, E]: MonadError[ZManaged[R, E, ?], E] =
@@ -92,14 +104,6 @@ trait CatsZManagedInstances extends CatsZManagedInstances1 {
       override def combine(x: ZManaged[R, E, A], y: ZManaged[R, E, A]): ZManaged[R, E, A] = x.zipWith(y)(ev.combine)
     }
 
-  implicit def liftIOZManagedInstances[R, A](
-    implicit ev: LiftIO[ZIO[R, Throwable, ?]]
-  ): LiftIO[ZManaged[R, Throwable, ?]] =
-    new LiftIO[ZManaged[R, Throwable, ?]] {
-      override def liftIO[A](ioa: CIO[A]): ZManaged[R, Throwable, A] =
-        ZManaged.fromEffect(ev.liftIO(ioa))
-    }
-
 }
 
 sealed trait CatsZManagedInstances1 {

interop-cats/shared/src/main/scala/zio/stream/interop/cats.scala

@@ -21,33 +21,35 @@ import cats.arrow._
 import zio._
 import zio.stream._
 
-object catz extends CatsInstances
+object catz extends CatsInstances {
+  object core extends CatsInstances
+}
 
 sealed abstract class CatsInstances extends CatsInstances1 {
-  implicit def alternativeInstance[R, E]: Alternative[ZStream[R, E, *]] =
+  implicit def zstreamAlternativeInstance[R, E]: Alternative[ZStream[R, E, *]] =
     new CatsAlternative[R, E]
 }
 
 sealed abstract class CatsInstances1 extends CatsInstances2 {
-  implicit def monoidKInstance[R, E]: MonoidK[ZStream[R, E, *]] =
+  implicit def zstreamMonoidKInstance[R, E]: MonoidK[ZStream[R, E, *]] =
     new CatsMonoidK[R, E]
 
-  implicit def bifunctorInstance[R]: Bifunctor[ZStream[R, *, *]] =
+  implicit def zstreamBifunctorInstance[R]: Bifunctor[ZStream[R, *, *]] =
     new CatsBifunctor[R] {}
 
-  implicit def zioArrowInstance[E]: ArrowChoice[ZStream[*, E, *]] = new CatsArrow[E]
+  implicit def zstreamArrowInstance[E]: ArrowChoice[ZStream[*, E, *]] = new CatsArrow[E]
 }
 
 sealed abstract class CatsInstances2 extends CatsInstances3 {
-  implicit def parallelInstance[R, E]: Parallel.Aux[ZStream[R, E, *], ParStream[R, E, *]] =
-    new CatsParallel[R, E](monadErrorInstance)
+  implicit def zstreamParallelInstance[R, E]: Parallel.Aux[ZStream[R, E, *], ParStream[R, E, *]] =
+    new CatsParallel[R, E](zstreamMonadErrorInstance)
 
-  implicit def semigroupKInstance[R, E: Semigroup]: SemigroupK[ZStream[R, E, *]] =
+  implicit def zstreamSemigroupKInstance[R, E: Semigroup]: SemigroupK[ZStream[R, E, *]] =
     new CatsSemigroupK[R, E]
 }
 
 sealed abstract class CatsInstances3 {
-  implicit def monadErrorInstance[R, E]: MonadError[ZStream[R, E, *], E] =
+  implicit def zstreamMonadErrorInstance[R, E]: MonadError[ZStream[R, E, *], E] =
     new CatsMonadError[R, E]
 }