support scala 2.12 (#129)

* support scala 2.12

* make some adjustments to the 2.12 compiler wrangling

* run scalafmt

* also scalafmtSbt because that's not included in scalafmtAll

* add github action step to run tests on 2.12

* sort gha scala versions

* satisfy our desire for order

Author: WtrLmmrs

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
       fail-fast: false
       matrix:
         java: ['adopt@1.11']
-        scala: ['2.13.13', '3.3.3']
+        scala: ['2.12.18', '2.13.13', '3.3.3']
     steps:
       - name: Checkout current branch
         uses: actions/checkout@v2.3.4

benchmarks/src/main/scala/com/devsisters/shardcake/Client.scala

@@ -1,9 +1,8 @@
 package com.devsisters.shardcake
 
-import com.devsisters.shardcake.Config
 import com.devsisters.shardcake.Server.Message.Ping
 import com.devsisters.shardcake.Server.PingPongEntity
-import zio._
+import zio.{ Config => _, _ }
 
 object Client {
   // self host should not be `localhost` to avoid optimization

benchmarks/src/main/scala/com/devsisters/shardcake/Server.scala

@@ -1,8 +1,7 @@
 package com.devsisters.shardcake
 
-import com.devsisters.shardcake.Config
 import com.devsisters.shardcake.interfaces.Storage
-import zio._
+import zio.{ Config => _, _ }
 import zio.stream.ZStream
 
 import java.util.concurrent.ForkJoinPool

build.sbt

@@ -1,6 +1,7 @@
+val scala212 = "2.12.18"
 val scala213 = "2.13.13"
 val scala3   = "3.3.3"
-val allScala = Seq(scala213, scala3)
+val allScala = Seq(scala212, scala213, scala3)
 
 val zioVersion            = "2.1.1"
 val zioGrpcVersion        = "0.6.2"
@@ -14,6 +15,7 @@ val redis4catsVersion     = "1.5.2"
 val redissonVersion       = "3.27.1"
 val scalaKryoVersion      = "1.0.2"
 val testContainersVersion = "0.41.3"
+val scalaCompatVersion    = "2.12.0"
 
 inThisBuild(
   List(
@@ -69,8 +71,9 @@ lazy val core = project
   .settings(
     libraryDependencies ++=
       Seq(
-        "dev.zio" %% "zio"         % zioVersion,
-        "dev.zio" %% "zio-streams" % zioVersion
+        "dev.zio"                %% "zio"                     % zioVersion,
+        "dev.zio"                %% "zio-streams"             % zioVersion,
+        "org.scala-lang.modules" %% "scala-collection-compat" % scalaCompatVersion
       )
   )
 

core/src/main/scala/com/devsisters/shardcake/PodAddress.scala

@@ -1,5 +1,7 @@
 package com.devsisters.shardcake
 
+import scala.collection.compat._
+
 case class PodAddress(host: String, port: Int) {
   override def toString: String = s"$host:$port"
 }

entities/src/main/scala/com/devsisters/shardcake/Sharding.scala

@@ -242,7 +242,7 @@ class Sharding private (
           (shardManager.notifyUnhealthyPod(pod) *>
             // just in case we missed the update from the pubsub, refresh assignments
             shardManager.getAssignments
-              .flatMap(updateAssignments(_, fromShardManager = true))).forkDaemon
+              .flatMap[Any, Throwable, Unit](updateAssignments(_, fromShardManager = true))).forkDaemon
         )
       }
 
@@ -337,7 +337,8 @@ class Sharding private (
         }
 
       def sendStream(entityId: String)(messages: ZStream[Any, Throwable, Msg]): Task[Unit] = {
-        val send = ReplyChannel.single[Unit].flatMap(sendStreamGeneric(entityId, messages, None, _))
+        val send =
+          ReplyChannel.single[Unit].flatMap[Any, Throwable, Unit](sendStreamGeneric(entityId, messages, None, _))
         timeout.fold(send)(t => send.timeout(t).unit)
       }
 

entities/src/main/scala/com/devsisters/shardcake/internal/ReplyChannel.scala

@@ -31,8 +31,13 @@ private[shardcake] object ReplyChannel {
     def fail(cause: Cause[Throwable]): UIO[Unit]                   = promise.failCause(cause).unit
     def replySingle(a: A): UIO[Unit]                               = promise.succeed(Some(a)).unit
     def replyStream(stream: ZStream[Any, Throwable, A]): UIO[Unit] =
-      stream.runHead.flatMap(promise.succeed(_)).catchAllCause(fail).fork.unit
-    val output: Task[Option[A]]                                    = promise.await.onError(fail)
+      stream.runHead
+        .flatMap(promise.succeed(_).unit)
+        .catchAllCause[Any, Nothing, Unit](fail)
+        .fork
+        .unit
+
+    val output: Task[Option[A]] = promise.await.onError(fail)
   }
 
   def single[A]: UIO[FromPromise[A]] =

entities/src/test/scala/com/devsisters/shardcake/ShardingSpec.scala

@@ -111,7 +111,7 @@ object ShardingSpec extends ZIOSpecDefault {
             _   <- Sharding.registerSingleton("singleton", p.succeed(()) *> ZIO.never)
             _   <- Sharding.registerScoped
             res <- p.await
-          } yield assertTrue(res == ())
+          } yield assertTrue(() == res)
         }
       },
       test("Send stream") {

examples/src/main/scala/example/complex/GuildApp.scala

@@ -7,6 +7,8 @@ import example.complex.GuildBehavior.GuildMessage.{ Join, Terminate }
 import example.complex.GuildBehavior._
 import zio.{ Config => _, _ }
 
+import scala.collection.compat._
+
 object GuildApp extends ZIOAppDefault {
   val config: ZLayer[Any, SecurityException, Config] =
     ZLayer(

manager/src/main/scala/com/devsisters/shardcake/ShardManager.scala

@@ -9,6 +9,7 @@ import zio._
 import zio.stream.ZStream
 
 import scala.annotation.tailrec
+import scala.collection.compat._
 
 /**
  * A component in charge of assigning and unassigning shards to/from pods
@@ -106,7 +107,7 @@ class ShardManager(
                                                                .ping(pod)
                                                                .timeout(config.pingTimeout)
                                                                .someOrFailException
-                                                               .fold(_ => Set(pod), _ => Set.empty)
+                                                               .fold(_ => Set(pod), _ => Set.empty[PodAddress])
                                                            )
                                                            .map(_.flatten)
         shardsToRemove                                 =
@@ -128,7 +129,7 @@ class ShardManager(
                                                              )
                                                            }
                                                            .map(_.unzip)
-                                                           .map { case (pods, shards) => (pods.flatten.toSet, shards.flatten.toSet) }
+                                                           .map { case (pods, shards) => (pods.flatten[PodAddress].toSet, shards.flatten[ShardId].toSet) }
         (failedUnassignedPods, failedUnassignedShards) = failed
         // remove assignments of shards that couldn't be unassigned, as well as faulty pods
         filteredAssignments                            = (readyAssignments -- failedUnassignedPods).map { case (pod, shards) =>
@@ -147,7 +148,7 @@ class ShardManager(
                                                                    eventsHub.publish(ShardingEvent.ShardsAssigned(pod, shards)).as(Set.empty)
                                                              )
                                                            }
-                                                           .map(_.flatten.toSet)
+                                                           .map(_.flatten[PodAddress].toSet)
         failedPods                                     = failedPingedPods ++ failedUnassignedPods ++ failedAssignedPods
         // check if failing pods are still up
         _                                             <- ZIO.foreachDiscard(failedPods)(notifyUnhealthyPod).forkDaemon
@@ -316,7 +317,9 @@ object ShardManager {
   ): (Map[PodAddress, Set[ShardId]], Map[PodAddress, Set[ShardId]]) = {
     val (_, assignments)    = shardsToRebalance.foldLeft((state.shardsPerPod, List.empty[(ShardId, PodAddress)])) {
       case ((shardsPerPod, assignments), shard) =>
-        val unassignedPods = assignments.flatMap { case (shard, _) => state.shards.get(shard).flatten }.toSet
+        val unassignedPods = assignments.flatMap { case (shard, _) =>
+          state.shards.get(shard).flatten[PodAddress]
+        }.toSet
         // find pod with least amount of shards
         shardsPerPod
           // keep only pods with the max version

storage-redis/src/main/scala/com/devsisters/shardcake/StorageRedis.scala

@@ -8,6 +8,8 @@ import zio.stream.ZStream
 import zio.stream.interop.fs2z._
 import zio.{ Task, ZIO, ZLayer }
 
+import scala.collection.compat._
+
 object StorageRedis {
   type fs2Stream[A] = fs2.Stream[Task, A]
   type Redis        = RedisCommands[Task, String, String] with PubSubCommands[fs2Stream, String, String]

storage-redisson/src/main/scala/com/devsisters/shardcake/StorageRedis.scala

@@ -9,6 +9,8 @@ import org.redisson.client.codec.StringCodec
 import zio.stream.ZStream
 import zio.{ Queue, Task, Unsafe, ZIO, ZLayer }
 
+import scala.collection.compat._
+
 object StorageRedis {
 
   /**