Add back Scala 2.12 (#1538)

* because it has ripple effect to Alpakka and then Cassandra plugin
* we need to coordinate this decision across all Akka projects, later

Reverts parts of #1448

.github/workflows/check-build-test.yml

@@ -66,9 +66,9 @@ jobs:
       - name: Cache Coursier cache
         uses: coursier/cache-action@v6
 
-      - name: Compile all code with fatal warnings for Java 11 and Scala 2.13
+      - name: Compile all code with fatal warnings for Java 11 and all Scala versions
         # Run locally with: env CI=true sbt 'clean ; Test/compile ; It/compile'
-        run: sbt "; Test/compile; It/compile"
+        run: sbt "++ Test/compile; It/compile"
 
   check-docs:
     name: Check Docs
@@ -105,8 +105,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - { java-version: [email protected],      scala-version: 2.13.8,  sbt-opts: '' }
-          - { java-version: [email protected], scala-version: 2.13.8,  sbt-opts: '-J-XX:+UnlockExperimentalVMOptions -J-XX:+UseJVMCICompiler' }
+          - { java-version: [email protected],      sbt-opts: '' }
+          - { java-version: [email protected], sbt-opts: '-J-XX:+UnlockExperimentalVMOptions -J-XX:+UseJVMCICompiler' }
     steps:
       - name: Checkout
         uses: actions/checkout@v2
@@ -128,7 +128,7 @@ jobs:
         uses: coursier/cache-action@v6
 
       - name: Run tests with Scala ${{ matrix.scala-version }} and Java ${{ matrix.java-version }}
-        run: sbt "++${{ matrix.scala-version }} test" ${{ matrix.sbt-opts }}
+        run: sbt ${{ matrix.sbt-opts }} "test"
 
       - name: Print logs on failure
         if: ${{ failure() }}

.github/workflows/release.yml

@@ -56,4 +56,4 @@ jobs:
           echo $GUSTAV_KEY | base64 -di > .github/id_rsa
           chmod 600 .github/id_rsa
           ssh-add .github/id_rsa
-          sbt "++2.13.8 docs/publishRsync"
+          sbt "docs/publishRsync"

benchmarks/src/main/scala/akka/kafka/benchmarks/InflightMetrics.scala

@@ -18,7 +18,7 @@ import javax.management.{Attribute, MBeanServerConnection, ObjectName}
 
 import scala.concurrent.duration.{FiniteDuration, _}
 import scala.concurrent.{ExecutionContext, Future}
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 private[benchmarks] trait InflightMetrics {
   import InflightMetrics._

benchmarks/src/main/scala/akka/kafka/benchmarks/KafkaConsumerBenchmarks.scala

@@ -14,7 +14,7 @@ import org.apache.kafka.clients.consumer.{OffsetAndMetadata, OffsetCommitCallbac
 import org.apache.kafka.common.TopicPartition
 
 import scala.annotation.tailrec
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 object KafkaConsumerBenchmarks extends LazyLogging {
   val pollTimeoutMs: Duration = Duration.ofMillis(50L)

benchmarks/src/main/scala/akka/kafka/benchmarks/KafkaConsumerFixtureGen.scala

@@ -9,7 +9,7 @@ import akka.kafka.benchmarks.app.RunTestCommand
 import org.apache.kafka.clients.consumer.{ConsumerConfig, KafkaConsumer}
 import org.apache.kafka.common.serialization.{ByteArrayDeserializer, StringDeserializer}
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 case class KafkaConsumerTestFixture(topic: String, msgCount: Int, consumer: KafkaConsumer[Array[Byte], String]) {
   def close(): Unit = consumer.close()

benchmarks/src/main/scala/akka/kafka/benchmarks/KafkaTransactionBenchmarks.scala

@@ -13,7 +13,7 @@ import org.apache.kafka.clients.producer.{Callback, ProducerRecord, RecordMetada
 import org.apache.kafka.common.TopicPartition
 
 import scala.annotation.tailrec
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.concurrent.duration.FiniteDuration
 
 object KafkaTransactionBenchmarks extends LazyLogging {

benchmarks/src/main/scala/akka/kafka/benchmarks/KafkaTransactionFixtureGen.scala

@@ -18,7 +18,7 @@ import org.apache.kafka.common.serialization.{
   StringSerializer
 }
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 case class KafkaTransactionTestFixture(sourceTopic: String,
                                        sinkTopic: String,

build.sbt

@@ -9,6 +9,7 @@ val Nightly = sys.env.get("EVENT_NAME").contains("schedule")
 // align ignore-prefixes in scripts/link-validator.conf
 // align in release.yml
 val Scala213 = "2.13.8"
+val Scala212 = "2.12.16"
 
 val AkkaBinaryVersionForDocs = "2.6"
 val akkaVersion = "2.6.19"
@@ -71,7 +72,7 @@ val commonSettings = Def.settings(
   startYear := Some(2014),
   licenses := Seq(("BUSL-1.1", url("https://raw.githubusercontent.com/akka/alpakka-kafka/master/LICENSE"))), // FIXME change s/master/v3.1.0/ when released
   description := "Alpakka is a Reactive Enterprise Integration library for Java and Scala, based on Reactive Streams and Akka.",
-  crossScalaVersions := Seq(Scala213),
+  crossScalaVersions := Seq(Scala213, Scala212),
   scalaVersion := Scala213,
   crossVersion := CrossVersion.binary,
   javacOptions ++= Seq(
@@ -81,9 +82,9 @@ val commonSettings = Def.settings(
   scalacOptions ++= Seq(
       "-encoding",
       "UTF-8", // yes, this is 2 args
-      "-Wconf:cat=feature:w,cat=deprecation:w,cat=unchecked:w,cat=lint:w,cat=unused:w,cat=w-flag:w"
+      "-Wconf:cat=feature:w,cat=deprecation&msg=.*JavaConverters.*:s,cat=unchecked:w,cat=lint:w,cat=unused:w,cat=w-flag:w"
     ) ++ {
-      if (insideCI.value && !Nightly) Seq("-Werror")
+      if (insideCI.value && !Nightly && scalaVersion.value != Scala212) Seq("-Werror")
       else Seq.empty
     },
   Compile / doc / scalacOptions := scalacOptions.value ++ Seq(

core/src/main/scala/akka/kafka/ConsumerMessage.scala

@@ -182,7 +182,7 @@ object ConsumerMessage {
    * Create an offset batch out of a list of offsets.
    */
   def createCommittableOffsetBatch[T <: Committable](offsets: java.util.List[T]): CommittableOffsetBatch = {
-    import scala.jdk.CollectionConverters._
+    import scala.collection.JavaConverters._
     CommittableOffsetBatch(offsets.asScala.toList)
   }
 

core/src/main/scala/akka/kafka/ConsumerSettings.scala

@@ -15,7 +15,7 @@ import com.typesafe.config.Config
 import org.apache.kafka.clients.consumer.{Consumer, ConsumerConfig, KafkaConsumer}
 import org.apache.kafka.common.serialization.Deserializer
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.compat.java8.OptionConverters._
 import scala.compat.java8.FutureConverters._
 import scala.concurrent.{ExecutionContext, Future}

core/src/main/scala/akka/kafka/Metadata.scala

@@ -11,7 +11,7 @@ import akka.actor.NoSerializationVerificationNeeded
 import org.apache.kafka.clients.consumer.{OffsetAndMetadata, OffsetAndTimestamp}
 import org.apache.kafka.common.{PartitionInfo, TopicPartition}
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.util.Try
 
 /**
@@ -40,7 +40,7 @@ object Metadata {
     def getResponse: Optional[java.util.Map[String, java.util.List[PartitionInfo]]] =
       response
         .map { m =>
-          Optional.of(m.view.mapValues(_.asJava).toMap.asJava)
+          Optional.of(m.iterator.map { case (k, v) => k -> v.asJava }.toMap.asJava)
         }
         .getOrElse(Optional.empty())
   }
@@ -90,7 +90,7 @@ object Metadata {
     def getResponse: Optional[java.util.Map[TopicPartition, java.lang.Long]] =
       response
         .map { m =>
-          Optional.of(m.view.mapValues(Long.box).toMap.asJava)
+          Optional.of(m.iterator.map { case (k, v) => k -> Long.box(v) }.toMap.asJava)
         }
         .getOrElse(Optional.empty())
   }
@@ -120,7 +120,7 @@ object Metadata {
     def getResponse: Optional[java.util.Map[TopicPartition, java.lang.Long]] =
       response
         .map { m =>
-          Optional.of(m.view.mapValues(Long.box).toMap.asJava)
+          Optional.of(m.iterator.map { case (k, v) => k -> Long.box(v) }.toMap.asJava)
         }
         .getOrElse(Optional.empty())
   }
@@ -164,7 +164,7 @@ object Metadata {
    * Warning: KafkaConsumer documentation states that this method may block indefinitely if the partition does not exist.
    */
   def createGetOffsetForTimes(timestampsToSearch: java.util.Map[TopicPartition, java.lang.Long]): GetOffsetsForTimes =
-    GetOffsetsForTimes(timestampsToSearch.asScala.view.mapValues(_.toLong).toMap)
+    GetOffsetsForTimes(timestampsToSearch.asScala.iterator.map { case (k, v) => k -> v.toLong }.toMap)
 
   /**
    * [[org.apache.kafka.clients.consumer.KafkaConsumer#committed()]]

core/src/main/scala/akka/kafka/ProducerMessage.scala

@@ -9,7 +9,7 @@ import akka.NotUsed
 import org.apache.kafka.clients.producer.{ProducerRecord, RecordMetadata}
 
 import scala.collection.immutable
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 /**
  * Classes that are used in both [[javadsl.Producer]] and

core/src/main/scala/akka/kafka/ProducerSettings.scala

@@ -14,7 +14,7 @@ import com.typesafe.config.Config
 import org.apache.kafka.clients.producer.{KafkaProducer, Producer, ProducerConfig}
 import org.apache.kafka.common.serialization.Serializer
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.compat.java8.OptionConverters._
 import scala.concurrent.duration._
 import akka.util.JavaDurationConverters._

core/src/main/scala/akka/kafka/Subscriptions.scala

@@ -12,7 +12,7 @@ import akka.kafka.internal.PartitionAssignmentHelpers.EmptyPartitionAssignmentHa
 import org.apache.kafka.common.TopicPartition
 
 import scala.annotation.varargs
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 sealed trait Subscription {
 

core/src/main/scala/akka/kafka/internal/ConfigSettings.scala

@@ -11,7 +11,7 @@ import akka.annotation.InternalApi
 import com.typesafe.config.{Config, ConfigObject}
 
 import scala.annotation.tailrec
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.concurrent.duration.Duration
 import akka.util.JavaDurationConverters._
 

core/src/main/scala/akka/kafka/internal/ConsumerProgressTracking.scala

@@ -8,7 +8,7 @@ import akka.annotation.InternalApi
 import org.apache.kafka.clients.consumer.{Consumer, ConsumerRecords, OffsetAndMetadata}
 import org.apache.kafka.common.TopicPartition
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 /**
  * Maintain our own OffsetAndTimestamp which can tolerate negative timestamps, which happen for old clients that

core/src/main/scala/akka/kafka/internal/ConsumerResetProtection.scala

@@ -15,7 +15,7 @@ import akka.kafka.internal.KafkaConsumerActor.Internal.Seek
 import org.apache.kafka.clients.consumer.{ConsumerRecord, ConsumerRecords, OffsetAndMetadata}
 import org.apache.kafka.common.TopicPartition
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 /**
  * Added as part of https://github.com/akka/alpakka-kafka/issues/1286 to avoid reprocessing data in case of Kafka

core/src/main/scala/akka/kafka/internal/ControlImplementations.scala

@@ -17,7 +17,7 @@ import akka.stream.stage.GraphStageLogic
 import akka.util.Timeout
 import org.apache.kafka.common.{Metric, MetricName}
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.compat.java8.FutureConverters.{CompletionStageOps, FutureOps}
 import scala.concurrent.{ExecutionContext, Future, Promise}
 

core/src/main/scala/akka/kafka/internal/KafkaConsumerActor.scala

@@ -31,7 +31,7 @@ import org.apache.kafka.common.errors.RebalanceInProgressException
 import org.apache.kafka.common.{Metric, MetricName, TopicPartition}
 
 import scala.annotation.nowarn
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.concurrent.{ExecutionContext, Future}
 import scala.concurrent.duration._
 import scala.util.{Success, Try}
@@ -546,7 +546,8 @@ import scala.util.control.NonFatal
     // commit partitions that are currently assigned to the consumer. For high volume topics, this can lead to small
     // amounts of replayed data during a rebalance, but for low volume topics we can ensure that consumers never appear
     // 'stuck' because of out-of-order commits from slow consumers.
-    val assignedOffsetsToCommit = aggregatedOffsets.view.filterKeys(consumer.assignment().contains).toMap
+    val assignedOffsetsToCommit =
+      aggregatedOffsets.iterator.filter { case (k, _) => consumer.assignment().contains(k) }.toMap
     progressTracker.commitRequested(assignedOffsetsToCommit)
     val replyTo = commitSenders
     // flush the data before calling `consumer.commitAsync` which might call the callback synchronously

core/src/main/scala/akka/kafka/internal/MessageBuilder.scala

@@ -22,7 +22,7 @@ import org.apache.kafka.common.requests.OffsetFetchResponse
 
 import scala.compat.java8.FutureConverters.FutureOps
 import scala.concurrent.Future
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 /** Internal API */
 @InternalApi
@@ -165,7 +165,8 @@ private[kafka] final class CommittableOffsetBatchImpl(
     private val committers: Map[GroupTopicPartition, KafkaAsyncConsumerCommitterRef],
     override val batchSize: Long
 ) extends CommittableOffsetBatch {
-  def offsets: Map[GroupTopicPartition, Long] = offsetsAndMetadata.view.mapValues(_.offset() - 1L).toMap
+  def offsets: Map[GroupTopicPartition, Long] =
+    offsetsAndMetadata.iterator.map { case (k, v) => k -> (v.offset() - 1L) }.toMap
 
   def updated(committable: Committable): CommittableOffsetBatch = committable match {
     case offset: CommittableOffset => updatedWithOffset(offset)

core/src/main/scala/akka/kafka/internal/PartitionAssignmentHelpers.scala

@@ -13,7 +13,7 @@ import akka.kafka.{AutoSubscription, RestrictedConsumer, TopicPartitionsAssigned
 import akka.stream.stage.AsyncCallback
 import org.apache.kafka.common.TopicPartition
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 /**
  * Internal API.

core/src/main/scala/akka/kafka/internal/SubSourceLogic.scala

@@ -108,8 +108,9 @@ private class SubSourceLogic[K, V, Msg](
     case (formerlyUnknown, offsetMap) =>
       val updatedFormerlyUnknown = formerlyUnknown -- (partitionsToRevoke ++ partitionsInStartup ++ pendingPartitions)
       // Filter out the offsetMap so that we don't re-seek for partitions that have been revoked
-      seekAndEmitSubSources(updatedFormerlyUnknown,
-                            offsetMap.view.filterKeys(k => !partitionsToRevoke.contains(k)).toMap)
+      seekAndEmitSubSources(updatedFormerlyUnknown, offsetMap.iterator.filterNot {
+        case (k, _) => partitionsToRevoke.contains(k)
+      }.toMap)
   }
 
   private val partitionAssignedCB = getAsyncCallback[Set[TopicPartition]] { assigned =>

core/src/main/scala/akka/kafka/internal/TransactionalProducerStage.scala

@@ -20,7 +20,7 @@ import org.apache.kafka.common.TopicPartition
 
 import scala.concurrent.Future
 import scala.concurrent.duration._
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 /**
  * INTERNAL API

core/src/main/scala/akka/kafka/internal/TransactionalSources.scala

@@ -113,7 +113,7 @@ private[internal] abstract class TransactionalSourceLogic[K, V, Msg](shape: Sour
 
   private def drainHandling: PartialFunction[(ActorRef, Any), Unit] = {
     case (sender, Committed(offsets)) =>
-      inFlightRecords.committed(offsets.view.mapValues(_.offset() - 1).toMap)
+      inFlightRecords.committed(offsets.iterator.map { case (k, v) => k -> (v.offset() - 1L) }.toMap)
       sender.tell(Done, sourceActor.ref)
     case (sender, CommittingFailure) => {
       log.info("Committing failed, resetting in flight offsets")
@@ -409,7 +409,7 @@ private final class TransactionalSubSourceStageLogic[K, V](
 
   private def drainHandling: PartialFunction[(ActorRef, Any), Unit] = {
     case (sender, Committed(offsets)) =>
-      inFlightRecords.committed(offsets.view.mapValues(_.offset() - 1).toMap)
+      inFlightRecords.committed(offsets.iterator.map { case (k, v) => k -> (v.offset() - 1L) }.toMap)
       sender ! Done
     case (sender, CommittingFailure) => {
       log.info("Committing failed, resetting in flight offsets")

core/src/main/scala/akka/kafka/javadsl/Consumer.scala

@@ -19,7 +19,7 @@ import akka.{Done, NotUsed}
 import org.apache.kafka.clients.consumer.ConsumerRecord
 import org.apache.kafka.common.{Metric, MetricName, TopicPartition}
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.compat.java8.FutureConverters._
 import scala.concurrent.duration.FiniteDuration
 

core/src/main/scala/akka/kafka/javadsl/MetadataClient.scala

@@ -16,7 +16,7 @@ import org.apache.kafka.common.{PartitionInfo, TopicPartition}
 
 import scala.compat.java8.FutureConverters._
 import scala.concurrent.ExecutionContextExecutor
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 class MetadataClient private (metadataClient: akka.kafka.scaladsl.MetadataClient) {
 
@@ -26,7 +26,7 @@ class MetadataClient private (metadataClient: akka.kafka.scaladsl.MetadataClient
     metadataClient
       .getBeginningOffsets(partitions.asScala.toSet)
       .map { beginningOffsets =>
-        beginningOffsets.view.mapValues(Long.box).toMap.asJava
+        beginningOffsets.iterator.map { case (k, v) => k -> Long.box(v) }.toMap.asJava
       }(ExecutionContexts.parasitic)
       .toJava
 
@@ -42,7 +42,7 @@ class MetadataClient private (metadataClient: akka.kafka.scaladsl.MetadataClient
     metadataClient
       .getEndOffsets(partitions.asScala.toSet)
       .map { endOffsets =>
-        endOffsets.view.mapValues(Long.box).toMap.asJava
+        endOffsets.iterator.map { case (k, v) => k -> Long.box(v) }.toMap.asJava
       }(ExecutionContexts.parasitic)
       .toJava
 
@@ -56,7 +56,7 @@ class MetadataClient private (metadataClient: akka.kafka.scaladsl.MetadataClient
     metadataClient
       .listTopics()
       .map { topics =>
-        topics.view.mapValues(partitionsInfo => partitionsInfo.asJava).toMap.asJava
+        topics.view.iterator.map { case (k, v) => k -> v.asJava }.toMap.asJava
       }(ExecutionContexts.parasitic)
       .toJava
 

testkit/src/main/scala/akka/kafka/testkit/ProducerResultFactory.scala

@@ -10,7 +10,7 @@ import akka.kafka.ProducerMessage
 import org.apache.kafka.clients.producer.{ProducerRecord, RecordMetadata}
 import org.apache.kafka.common.TopicPartition
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 import scala.collection.immutable
 
 /**

testkit/src/main/scala/akka/kafka/testkit/internal/KafkaTestKit.scala

@@ -18,7 +18,7 @@ import org.apache.kafka.clients.consumer.ConsumerConfig
 import org.apache.kafka.common.serialization.{Deserializer, Serializer, StringDeserializer, StringSerializer}
 import org.slf4j.Logger
 
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 /**
  * Common functions for scaladsl and javadsl Testkit.

testkit/src/main/scala/akka/kafka/testkit/internal/TestcontainersKafka.scala

@@ -12,7 +12,7 @@ import org.testcontainers.containers.GenericContainer
 import org.testcontainers.utility.DockerImageName
 
 import scala.compat.java8.OptionConverters._
-import scala.jdk.CollectionConverters._
+import scala.collection.JavaConverters._
 
 object TestcontainersKafka {
   trait Spec extends KafkaSpec {