Seal the API traits

Sealing the traits gives us more freedom regarding binary compatibility.
We can add new methods later on without taking the risk to break some
extra implementation done in some using code.
It gives us the flexibility to have several modules implementing our
traits, from within the module, without opening it to the outside.

This prevents easily adding new queue providers from outside the
library, which is fine as the library makes some asumption on the
underlying systems and the way they are used to make the higher level
features work properly.

This approach is borrowed from fs2, e.g. for the `Files` and `Processes`
API.

.scalafix.conf

@@ -7,3 +7,4 @@ OrganizeImports {
 rules = [
   OrganizeImports
 ]
+OrganizeImports.targetDialect = Scala2

aws/sqs/src/main/scala/com/commercetools/queue/aws/sqs/SQSAdministration.scala

@@ -24,15 +24,15 @@ import cats.syntax.functorFilter._
 import cats.syntax.monadError._
 import cats.syntax.option._
 import com.commercetools.queue.aws.sqs.makeQueueException
-import com.commercetools.queue.{MalformedQueueConfigurationException, QueueAdministration, QueueConfiguration, QueueDoesNotExistException}
+import com.commercetools.queue.{MalformedQueueConfigurationException, QueueConfiguration, QueueDoesNotExistException, UnsealedQueueAdministration}
 import software.amazon.awssdk.services.sqs.SqsAsyncClient
 import software.amazon.awssdk.services.sqs.model.{CreateQueueRequest, DeleteQueueRequest, GetQueueAttributesRequest, QueueAttributeName, SetQueueAttributesRequest}
 
 import scala.concurrent.duration._
 import scala.jdk.CollectionConverters._
 
 class SQSAdministration[F[_]](client: SqsAsyncClient, getQueueUrl: String => F[String])(implicit F: Async[F])
-  extends QueueAdministration[F] {
+  extends UnsealedQueueAdministration[F] {
 
   override def create(name: String, messageTTL: FiniteDuration, lockTTL: FiniteDuration): F[Unit] =
     F.fromCompletableFuture {

aws/sqs/src/main/scala/com/commercetools/queue/aws/sqs/SQSClient.scala

@@ -19,7 +19,7 @@ package com.commercetools.queue.aws.sqs
 import cats.effect.{Async, Resource}
 import cats.syntax.functor._
 import cats.syntax.monadError._
-import com.commercetools.queue.{Deserializer, QueueAdministration, QueueClient, QueuePublisher, QueueStatistics, QueueSubscriber, Serializer}
+import com.commercetools.queue.{Deserializer, QueueAdministration, QueuePublisher, QueueStatistics, QueueSubscriber, Serializer, UnsealedQueueClient}
 import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider
 import software.amazon.awssdk.http.async.SdkAsyncHttpClient
 import software.amazon.awssdk.regions.Region
@@ -28,7 +28,7 @@ import software.amazon.awssdk.services.sqs.model.GetQueueUrlRequest
 
 import java.net.URI
 
-class SQSClient[F[_]] private (client: SqsAsyncClient)(implicit F: Async[F]) extends QueueClient[F] {
+class SQSClient[F[_]] private (client: SqsAsyncClient)(implicit F: Async[F]) extends UnsealedQueueClient[F] {
 
   private def getQueueUrl(name: String): F[String] =
     F.fromCompletableFuture {

aws/sqs/src/main/scala/com/commercetools/queue/aws/sqs/SQSPublisher.scala

@@ -17,7 +17,7 @@
 package com.commercetools.queue.aws.sqs
 
 import cats.effect.{Async, Resource}
-import com.commercetools.queue.{QueuePublisher, QueuePusher, Serializer}
+import com.commercetools.queue.{QueuePusher, Serializer, UnsealedQueuePublisher}
 import software.amazon.awssdk.services.sqs.SqsAsyncClient
 
 class SQSPublisher[F[_], T](
@@ -27,7 +27,7 @@ class SQSPublisher[F[_], T](
 )(implicit
   F: Async[F],
   serializer: Serializer[T])
-  extends QueuePublisher[F, T] {
+  extends UnsealedQueuePublisher[F, T] {
 
   override def pusher: Resource[F, QueuePusher[F, T]] =
     Resource.eval(getQueueUrl).map(new SQSPusher(queueName, client, _))

aws/sqs/src/main/scala/com/commercetools/queue/aws/sqs/SQSPuller.scala

@@ -21,7 +21,7 @@ import cats.effect.syntax.concurrent._
 import cats.syntax.flatMap._
 import cats.syntax.functor._
 import cats.syntax.monadError._
-import com.commercetools.queue.{Deserializer, MessageContext, QueuePuller}
+import com.commercetools.queue.{Deserializer, MessageContext, UnsealedQueuePuller}
 import fs2.Chunk
 import software.amazon.awssdk.services.sqs.SqsAsyncClient
 import software.amazon.awssdk.services.sqs.model.{MessageSystemAttributeName, ReceiveMessageRequest}
@@ -39,7 +39,7 @@ class SQSPuller[F[_], T](
 )(implicit
   F: Async[F],
   deserializer: Deserializer[T])
-  extends QueuePuller[F, T] {
+  extends UnsealedQueuePuller[F, T] {
 
   override def pullBatch(batchSize: Int, waitingTime: FiniteDuration): F[Chunk[MessageContext[F, T]]] =
     F.fromCompletableFuture {

aws/sqs/src/main/scala/com/commercetools/queue/aws/sqs/SQSStatistics.scala

@@ -18,11 +18,11 @@ package com.commercetools.queue.aws.sqs
 
 import cats.effect.{Async, Resource}
 import cats.syntax.functor._
-import com.commercetools.queue.{QueueStatistics, QueueStatsFetcher}
+import com.commercetools.queue.{QueueStatsFetcher, UnsealedQueueStatistics}
 import software.amazon.awssdk.services.sqs.SqsAsyncClient
 
 class SQSStatistics[F[_]](val queueName: String, client: SqsAsyncClient, getQueueUrl: F[String])(implicit F: Async[F])
-  extends QueueStatistics[F] {
+  extends UnsealedQueueStatistics[F] {
 
   override def fetcher: Resource[F, QueueStatsFetcher[F]] =
     Resource.eval(getQueueUrl.map(new SQSStatisticsFetcher[F](queueName, client, _)))

aws/sqs/src/main/scala/com/commercetools/queue/aws/sqs/SQSStatisticsFetcher.scala

@@ -22,15 +22,15 @@ import cats.syntax.functor._
 import cats.syntax.monadError._
 import cats.syntax.option._
 import cats.syntax.traverse._
-import com.commercetools.queue.{MalformedQueueConfigurationException, QueueStats, QueueStatsFetcher}
+import com.commercetools.queue.{MalformedQueueConfigurationException, QueueStats, UnsealedQueueStatsFetcher}
 import software.amazon.awssdk.services.sqs.SqsAsyncClient
 import software.amazon.awssdk.services.sqs.model.{GetQueueAttributesRequest, QueueAttributeName}
 
 import scala.collection.mutable
 import scala.jdk.CollectionConverters._
 
 class SQSStatisticsFetcher[F[_]](val queueName: String, client: SqsAsyncClient, queueUrl: String)(implicit F: Async[F])
-  extends QueueStatsFetcher[F] {
+  extends UnsealedQueueStatsFetcher[F] {
 
   override def fetch: F[QueueStats] =
     (for {

aws/sqs/src/main/scala/com/commercetools/queue/aws/sqs/SQSSubscriber.scala

@@ -18,7 +18,7 @@ package com.commercetools.queue.aws.sqs
 
 import cats.effect.{Async, Resource}
 import cats.syntax.all._
-import com.commercetools.queue.{Deserializer, QueuePuller, QueueSubscriber}
+import com.commercetools.queue.{Deserializer, QueuePuller, UnsealedQueueSubscriber}
 import software.amazon.awssdk.services.sqs.SqsAsyncClient
 import software.amazon.awssdk.services.sqs.model.{GetQueueAttributesRequest, QueueAttributeName}
 
@@ -29,7 +29,7 @@ class SQSSubscriber[F[_], T](
 )(implicit
   F: Async[F],
   deserializer: Deserializer[T])
-  extends QueueSubscriber[F, T] {
+  extends UnsealedQueueSubscriber[F, T] {
 
   private def getLockTTL(queueUrl: String): F[Int] =
     F.fromCompletableFuture {

azure/service-bus/src/main/scala/com/commercetools/queue/azure/servicebus/ServiceBusAdministration.scala

@@ -21,7 +21,7 @@ import cats.syntax.functor._
 import cats.syntax.monadError._
 import com.azure.messaging.servicebus.administration.ServiceBusAdministrationClient
 import com.azure.messaging.servicebus.administration.models.CreateQueueOptions
-import com.commercetools.queue.{QueueAdministration, QueueConfiguration}
+import com.commercetools.queue.{QueueConfiguration, UnsealedQueueAdministration}
 
 import java.time.Duration
 import scala.concurrent.duration._
@@ -30,7 +30,7 @@ class ServiceBusAdministration[F[_]](
   client: ServiceBusAdministrationClient,
   newQueueSettings: NewQueueSettings
 )(implicit F: Async[F])
-  extends QueueAdministration[F] {
+  extends UnsealedQueueAdministration[F] {
 
   override def create(name: String, messageTTL: FiniteDuration, lockTTL: FiniteDuration): F[Unit] =
     F.blocking {

azure/service-bus/src/main/scala/com/commercetools/queue/azure/servicebus/ServiceBusClient.scala

@@ -21,14 +21,14 @@ import com.azure.core.credential.TokenCredential
 import com.azure.core.util.ClientOptions
 import com.azure.messaging.servicebus.ServiceBusClientBuilder
 import com.azure.messaging.servicebus.administration.ServiceBusAdministrationClientBuilder
-import com.commercetools.queue.{Deserializer, QueueAdministration, QueueClient, QueuePublisher, QueueStatistics, QueueSubscriber, Serializer}
+import com.commercetools.queue.{Deserializer, QueueAdministration, QueuePublisher, QueueStatistics, QueueSubscriber, Serializer, UnsealedQueueClient}
 
 class ServiceBusClient[F[_]] private (
   clientBuilder: ServiceBusClientBuilder,
   adminBuilder: ServiceBusAdministrationClientBuilder,
   newQueueSettings: NewQueueSettings
 )(implicit F: Async[F])
-  extends QueueClient[F] {
+  extends UnsealedQueueClient[F] {
 
   override def administration: QueueAdministration[F] =
     new ServiceBusAdministration(adminBuilder.buildClient(), newQueueSettings)

azure/service-bus/src/main/scala/com/commercetools/queue/azure/servicebus/ServiceBusPuller.scala

@@ -22,7 +22,7 @@ import cats.syntax.flatMap._
 import cats.syntax.functor._
 import cats.syntax.monadError._
 import com.azure.messaging.servicebus.ServiceBusReceiverClient
-import com.commercetools.queue.{Deserializer, MessageContext, QueuePuller}
+import com.commercetools.queue.{Deserializer, MessageContext, UnsealedQueuePuller}
 import fs2.Chunk
 
 import java.time.Duration
@@ -35,7 +35,7 @@ class ServiceBusPuller[F[_], Data](
 )(implicit
   F: Async[F],
   deserializer: Deserializer[Data])
-  extends QueuePuller[F, Data] {
+  extends UnsealedQueuePuller[F, Data] {
 
   override def pullBatch(batchSize: Int, waitingTime: FiniteDuration): F[Chunk[MessageContext[F, Data]]] = F
     .blocking {

azure/service-bus/src/main/scala/com/commercetools/queue/azure/servicebus/ServiceBusQueuePublisher.scala

@@ -18,15 +18,15 @@ package com.commercetools.queue.azure.servicebus
 
 import cats.effect.{Async, Resource}
 import com.azure.messaging.servicebus.ServiceBusClientBuilder
-import com.commercetools.queue.{QueuePublisher, QueuePusher, Serializer}
+import com.commercetools.queue.{QueuePusher, Serializer, UnsealedQueuePublisher}
 
 class ServiceBusQueuePublisher[F[_], Data](
   val queueName: String,
   clientBuilder: ServiceBusClientBuilder
 )(implicit
   F: Async[F],
   serializer: Serializer[Data])
-  extends QueuePublisher[F, Data] {
+  extends UnsealedQueuePublisher[F, Data] {
 
   override def pusher: Resource[F, QueuePusher[F, Data]] =
     Resource

azure/service-bus/src/main/scala/com/commercetools/queue/azure/servicebus/ServiceBusQueueSubscriber.scala

@@ -18,15 +18,15 @@ package com.commercetools.queue.azure.servicebus
 import cats.effect.{Async, Resource}
 import com.azure.messaging.servicebus.ServiceBusClientBuilder
 import com.azure.messaging.servicebus.models.ServiceBusReceiveMode
-import com.commercetools.queue.{Deserializer, QueuePuller, QueueSubscriber}
+import com.commercetools.queue.{Deserializer, QueuePuller, UnsealedQueueSubscriber}
 
 class ServiceBusQueueSubscriber[F[_], Data](
   val queueName: String,
   builder: ServiceBusClientBuilder
 )(implicit
   F: Async[F],
   deserializer: Deserializer[Data])
-  extends QueueSubscriber[F, Data] {
+  extends UnsealedQueueSubscriber[F, Data] {
 
   override def puller: Resource[F, QueuePuller[F, Data]] = Resource
     .fromAutoCloseable {

azure/service-bus/src/main/scala/com/commercetools/queue/azure/servicebus/ServiceBusStatistics.scala

@@ -18,13 +18,13 @@ package com.commercetools.queue.azure.servicebus
 
 import cats.effect.{Async, Resource}
 import com.azure.messaging.servicebus.administration.ServiceBusAdministrationClientBuilder
-import com.commercetools.queue.{QueueStatistics, QueueStatsFetcher}
+import com.commercetools.queue.{QueueStatsFetcher, UnsealedQueueStatistics}
 
 class ServiceBusStatistics[F[_]](
   val queueName: String,
   builder: ServiceBusAdministrationClientBuilder
 )(implicit F: Async[F])
-  extends QueueStatistics[F] {
+  extends UnsealedQueueStatistics[F] {
 
   override def fetcher: Resource[F, QueueStatsFetcher[F]] =
     Resource.eval {

azure/service-bus/src/main/scala/com/commercetools/queue/azure/servicebus/ServiceBusStatsFetcher.scala

@@ -20,10 +20,10 @@ import cats.effect.Async
 import cats.syntax.functor._
 import cats.syntax.monadError._
 import com.azure.messaging.servicebus.administration.ServiceBusAdministrationClient
-import com.commercetools.queue.{QueueStats, QueueStatsFetcher}
+import com.commercetools.queue.{QueueStats, UnsealedQueueStatsFetcher}
 
 class ServiceBusStatsFetcher[F[_]](val queueName: String, client: ServiceBusAdministrationClient)(implicit F: Async[F])
-  extends QueueStatsFetcher[F] {
+  extends UnsealedQueueStatsFetcher[F] {
 
   override def fetch: F[QueueStats] =
     F.blocking(client.getQueueRuntimeProperties(queueName))

core/src/main/scala/com/commercetools/queue/QueueAdministration.scala

@@ -21,7 +21,7 @@ import scala.concurrent.duration.FiniteDuration
 /**
  * Interface that gives access to the queue administration capabilities.
  */
-trait QueueAdministration[F[_]] {
+sealed trait QueueAdministration[F[_]] {
 
   /** Creates a queue with the given name, message TTL and lock TTL. */
   def create(name: String, messageTTL: FiniteDuration, lockTTL: FiniteDuration): F[Unit]
@@ -42,3 +42,5 @@ trait QueueAdministration[F[_]] {
   def exists(name: String): F[Boolean]
 
 }
+
+private[queue] trait UnsealedQueueAdministration[F[_]] extends QueueAdministration[F]

core/src/main/scala/com/commercetools/queue/QueueClient.scala

@@ -21,7 +21,7 @@ package com.commercetools.queue
  * A client will manage connection pools and has knowledge of the underlying queue system.
  * A client should be managed as a resource to cleanup connections when not need anymore.
  */
-trait QueueClient[F[_]] {
+sealed trait QueueClient[F[_]] {
 
   /**
    * Gives access to adminsitrative API.
@@ -44,3 +44,5 @@ trait QueueClient[F[_]] {
   def subscribe[T: Deserializer](name: String): QueueSubscriber[F, T]
 
 }
+
+private[queue] trait UnsealedQueueClient[F[_]] extends QueueClient[F]

core/src/main/scala/com/commercetools/queue/QueuePublisher.scala

@@ -22,7 +22,7 @@ import fs2.Stream
 /**
  * The interface to publish to a queue.
  */
-abstract class QueuePublisher[F[_], T](implicit F: MonadCancel[F, Throwable]) {
+sealed abstract class QueuePublisher[F[_], T](implicit F: MonadCancel[F, Throwable]) {
 
   /** The queue name to which this publisher publishes. */
   def queueName: String
@@ -50,6 +50,9 @@ abstract class QueuePublisher[F[_], T](implicit F: MonadCancel[F, Throwable]) {
 
 }
 
+abstract private[queue] class UnsealedQueuePublisher[F[_], T](implicit F: MonadCancel[F, Throwable])
+  extends QueuePublisher[F, T]
+
 object QueuePublisher {
 
   /**

core/src/main/scala/com/commercetools/queue/QueuePuller.scala

@@ -23,7 +23,7 @@ import scala.concurrent.duration.FiniteDuration
 /**
  * A queue puller allows for pulling batches of elements from a queue individually.
  */
-trait QueuePuller[F[_], T] {
+sealed trait QueuePuller[F[_], T] {
 
   /** The queue name from which this puller is pulling. */
   def queueName: String
@@ -44,3 +44,5 @@ trait QueuePuller[F[_], T] {
   def pullBatch(batchSize: Int, waitingTime: FiniteDuration): F[Chunk[MessageContext[F, T]]]
 
 }
+
+private[queue] trait UnsealedQueuePuller[F[_], T] extends QueuePuller[F, T]

core/src/main/scala/com/commercetools/queue/QueueStatistics.scala

@@ -25,7 +25,7 @@ import scala.concurrent.duration.FiniteDuration
 /**
  * The base interface to fetch statistics from a queue.
  */
-abstract class QueueStatistics[F[_]](implicit F: Temporal[F]) {
+sealed abstract class QueueStatistics[F[_]](implicit F: Temporal[F]) {
 
   /** The queue name from which to pull statistics. */
   def queueName: String
@@ -62,3 +62,5 @@ abstract class QueueStatistics[F[_]](implicit F: Temporal[F]) {
     stream(interval).rethrow
 
 }
+
+abstract private[queue] class UnsealedQueueStatistics[F[_]](implicit F: Temporal[F]) extends QueueStatistics[F]

core/src/main/scala/com/commercetools/queue/QueueStatsFetcher.scala

@@ -19,11 +19,13 @@ package com.commercetools.queue
 /**
  * A queue statistics fetcher allows for fetching statistics a queue individually.
  */
-trait QueueStatsFetcher[F[_]] {
+sealed trait QueueStatsFetcher[F[_]] {
 
   /**
    * Fetches the current statistics for the queue.
    */
   def fetch: F[QueueStats]
 
 }
+
+private[queue] trait UnsealedQueueStatsFetcher[F[_]] extends QueueStatsFetcher[F]

core/src/main/scala/com/commercetools/queue/QueueSubscriber.scala

@@ -26,7 +26,7 @@ import scala.concurrent.duration.FiniteDuration
 /**
  * The base interface to subscribe to a queue.
  */
-abstract class QueueSubscriber[F[_], T](implicit F: Concurrent[F]) {
+sealed abstract class QueueSubscriber[F[_], T](implicit F: Concurrent[F]) {
 
   /** The queue name to which this subscriber subscribes. */
   def queueName: String
@@ -175,3 +175,5 @@ abstract class QueueSubscriber[F[_], T](implicit F: Concurrent[F]) {
     process[Res](batchSize, waitingTime, QueuePublisher.noop)((msg: Message[F, T]) =>
       handler.handle(msg).widen[Decision[Res]])
 }
+
+abstract private[queue] class UnsealedQueueSubscriber[F[_], T](implicit F: Concurrent[F]) extends QueueSubscriber[F, T]

core/src/test/scala/com/commercetools/queue/testing/TestQueuePublisher.scala

@@ -17,9 +17,9 @@
 package com.commercetools.queue.testing
 
 import cats.effect.{IO, Resource}
-import com.commercetools.queue.{QueuePublisher, QueuePusher}
+import com.commercetools.queue.{QueuePusher, UnsealedQueuePublisher}
 
-class TestQueuePublisher[T](queue: TestQueue[T]) extends QueuePublisher[IO, T] {
+class TestQueuePublisher[T](queue: TestQueue[T]) extends UnsealedQueuePublisher[IO, T] {
 
   override val queueName = queue.name
 

core/src/test/scala/com/commercetools/queue/testing/TestQueuePuller.scala

@@ -17,12 +17,12 @@
 package com.commercetools.queue.testing
 
 import cats.effect.IO
-import com.commercetools.queue.{MessageContext, QueuePuller}
+import com.commercetools.queue.{MessageContext, UnsealedQueuePuller}
 import fs2.Chunk
 
 import scala.concurrent.duration.FiniteDuration
 
-class TestQueuePuller[T](queue: TestQueue[T]) extends QueuePuller[IO, T] {
+class TestQueuePuller[T](queue: TestQueue[T]) extends UnsealedQueuePuller[IO, T] {
 
   override val queueName: String = queue.name
 

core/src/test/scala/com/commercetools/queue/testing/TestQueueSubscriber.scala

@@ -17,9 +17,9 @@
 package com.commercetools.queue.testing
 
 import cats.effect.{IO, Resource}
-import com.commercetools.queue.{QueuePuller, QueueSubscriber}
+import com.commercetools.queue.{QueuePuller, UnsealedQueueSubscriber}
 
-class TestQueueSubscriber[T](queue: TestQueue[T]) extends QueueSubscriber[IO, T] {
+class TestQueueSubscriber[T](queue: TestQueue[T]) extends UnsealedQueueSubscriber[IO, T] {
 
   override val queueName: String = queue.name