Merge pull request #74 from cr-org/type-level-builders

Type-level builders

Author: gvolpe

build.sbt

@@ -1,6 +1,8 @@
 import Dependencies._
 import Settings._
 
+scalaVersion in ThisBuild := "2.13.2"
+
 lazy val `neutron-core` = (project in file("core"))
   .enablePlugins(AutomateHeaderPlugin)
   .settings(commonSettings)

core/src/it/scala/cr/pulsar/PulsarSpec.scala

@@ -26,16 +26,27 @@ import java.util.UUID
 
 class PulsarSpec extends PulsarSuite {
 
-  val sub   = (s: String) => Subscription(Subscription.Name(s)).withType(Subscription.Type.Failover)
-  val topic = (s: String) => Topic(Topic.Name(s), cfg)
+  val sub = (s: String) =>
+    Subscription.Builder
+      .withName(Subscription.Name(s))
+      .withType(Subscription.Type.Failover)
+      .build
+
+  val topic = (s: String) =>
+    Topic.Builder
+      .withName(Topic.Name(s))
+      .withConfig(cfg)
+      .build
+
   val batch = Producer.Batching.Disabled
   val shard = (_: Event) => Producer.MessageKey.Default
 
   withPulsarClient { client =>
     test("A message is published and consumed successfully") {
       val res: Resource[IO, (Consumer[IO, Event], Producer[IO, Event])] =
         for {
-          consumer <- Consumer.create[IO, Event](client, topic("happy-path"), sub("happy-path"))
+          consumer <- Consumer
+                       .create[IO, Event](client, topic("happy-path"), sub("happy-path"))
           producer <- Producer.create[IO, Event](client, topic("happy-path"))
         } yield consumer -> producer
 
@@ -68,7 +79,8 @@ class PulsarSpec extends PulsarSuite {
     test("A message is published and nack'ed when consumer fails to decode it") {
       val res: Resource[IO, (Consumer[IO, Event], Producer[IO, String])] =
         for {
-          consumer <- Consumer.create[IO, Event](client, topic("auto-nack"), sub("auto-nack"))
+          consumer <- Consumer
+                       .create[IO, Event](client, topic("auto-nack"), sub("auto-nack"))
           producer <- Producer.create[IO, String](client, topic("auto-nack"))
         } yield consumer -> producer
 
@@ -80,7 +92,8 @@ class PulsarSpec extends PulsarSuite {
               val consume =
                 consumer.autoSubscribe
                   .handleErrorWith {
-                    case Consumer.DecodingFailure(data) => Stream.eval(latch.complete(data))
+                    case Consumer.DecodingFailure(data) =>
+                      Stream.eval(latch.complete(data))
                   }
 
               val testMessage = "Consumer will fail to decode this message"
@@ -105,7 +118,10 @@ class PulsarSpec extends PulsarSuite {
     ) {
       val makeSub =
         (n: String) =>
-          Subscription(Subscription.Name(n)).withType(Subscription.Type.KeyShared)
+          Subscription.Builder
+            .withName(Subscription.Name(n))
+            .withType(Subscription.Type.KeyShared)
+            .build
 
       val opts =
         Producer.Options[IO, Event]().withShardKey(_.shardKey).withBatching(batch)

core/src/it/scala/cr/pulsar/PulsarSuite.scala

@@ -41,8 +41,7 @@ abstract class PulsarSuite extends FunSuite {
 
   override def beforeAll(): Unit = {
     super.beforeAll()
-    val (cli, release) =
-      Pulsar.create[IO](cfg.serviceUrl).allocated.unsafeRunSync()
+    val (cli, release) = Pulsar.create[IO](cfg.url).allocated.unsafeRunSync()
     this.client = cli
     this.close = release
     latch.complete(()).unsafeRunSync()
@@ -80,6 +79,6 @@ abstract class PulsarSuite extends FunSuite {
       }
   }
 
-  lazy val cfg = Config.Default
+  lazy val cfg = Config.Builder.default
 
 }

core/src/main/scala/cr/pulsar/Config.scala

@@ -18,6 +18,7 @@ package cr.pulsar
 
 import Config._
 import io.estatico.newtype.macros._
+import scala.annotation.implicitNotFound
 
 /**
   * Basic Pulsar configuration to establish
@@ -26,47 +27,69 @@ import io.estatico.newtype.macros._
 sealed abstract class Config {
   val tenant: PulsarTenant
   val namespace: PulsarNamespace
-  val serviceUrl: PulsarURL
-  def withTenant(_tenant: PulsarTenant): Config
-  def withNamespace(_namespace: PulsarNamespace): Config
-  def withURL(_url: PulsarURL): Config
+  val url: PulsarURL
 }
 
 object Config {
   @newtype case class PulsarTenant(value: String)
   @newtype case class PulsarNamespace(value: String)
   @newtype case class PulsarURL(value: String)
 
-  private case class ConfigImpl(
-      tenant: PulsarTenant,
-      namespace: PulsarNamespace,
-      serviceUrl: PulsarURL
-  ) extends Config {
-    def withTenant(_tenant: PulsarTenant): Config =
-      copy(tenant = _tenant)
-    def withNamespace(_namespace: PulsarNamespace): Config =
-      copy(namespace = _namespace)
-    def withURL(_serviceUrl: PulsarURL): Config =
-      copy(serviceUrl = _serviceUrl)
+  /**************** Type-level builder ******************/
+  sealed trait Info
+  object Info {
+    sealed trait Empty extends Info
+    sealed trait Namespace extends Info
+    sealed trait Tenant extends Info
+    sealed trait URL extends Info
+
+    type Mandatory = Empty with Namespace with Tenant with URL
+  }
+
+  case class ConfigBuilder[I <: Info] protected (
+      _tenant: PulsarTenant = PulsarTenant(""),
+      _namespace: PulsarNamespace = PulsarNamespace(""),
+      _url: PulsarURL = PulsarURL("")
+  ) {
+    def withTenant(tenant: PulsarTenant): ConfigBuilder[I with Info.Tenant] =
+      this.copy(_tenant = tenant)
+
+    def withNameSpace(namespace: PulsarNamespace): ConfigBuilder[I with Info.Namespace] =
+      this.copy(_namespace = namespace)
+
+    def withURL(url: PulsarURL): ConfigBuilder[I with Info.URL] =
+      this.copy(_url = url)
+
+    /**
+      * It creates a new configuration.
+      */
+    def build(
+        implicit @implicitNotFound(
+          "Tenant, Namespace and URL are mandatory. To create a default configuration, use Config.Builder.default instead."
+        ) ev: I =:= Info.Mandatory
+    ): Config =
+      new Config {
+        val tenant    = _tenant
+        val namespace = _namespace
+        val url       = _url
+      }
+
+    /**
+      * It creates a new configuration with the following default values:
+      *
+      * - tenant: "public"
+      * - namespace: "default"
+      * - url: "pulsar://localhost:6650"
+      */
+    def default: Config =
+      Config.Builder
+        .withTenant(PulsarTenant("public"))
+        .withNameSpace(PulsarNamespace("default"))
+        .withURL(PulsarURL("pulsar://localhost:6650"))
+        .build
+
   }
 
-  def apply(
-      tenant: PulsarTenant,
-      namespace: PulsarNamespace,
-      serviceUrl: PulsarURL
-  ): Config = ConfigImpl(tenant, namespace, serviceUrl)
+  object Builder extends ConfigBuilder[Info.Empty]()
 
-  /**
-    * It creates a default configuration.
-    *
-    * - tenant: "public"
-    * - namespace: "default"
-    * - url: "pulsar://localhost:6650"
-    */
-  def Default: Config =
-    ConfigImpl(
-      PulsarTenant("public"),
-      PulsarNamespace("default"),
-      PulsarURL("pulsar://localhost:6650")
-    )
 }

core/src/main/scala/cr/pulsar/Subscription.scala

@@ -18,14 +18,12 @@ package cr.pulsar
 
 import io.estatico.newtype.macros.newtype
 import org.apache.pulsar.client.api.{ SubscriptionMode, SubscriptionType }
+import scala.annotation.implicitNotFound
 
-// Builder-style abstract class instead of case class to allow for bincompat-friendly extension in future versions.
 sealed abstract class Subscription {
   val name: Subscription.Name
   val `type`: Subscription.Type
   val mode: Subscription.Mode
-  def withType(_type: Subscription.Type): Subscription
-  def withMode(_mode: Subscription.Mode): Subscription
 }
 
 /**
@@ -73,25 +71,50 @@ object Subscription {
     }
   }
 
-  private case class SubscriptionImpl(
-      name: Subscription.Name,
-      `type`: Subscription.Type,
-      mode: Subscription.Mode
-  ) extends Subscription {
-    def withType(_type: Subscription.Type): Subscription =
-      copy(`type` = _type)
-    def withMode(_mode: Subscription.Mode): Subscription =
-      copy(mode = _mode)
+  /**************** Type-level builder ******************/
+  sealed trait Info
+  object Info {
+    sealed trait Empty extends Info
+    sealed trait Name extends Info
+    sealed trait Mode extends Info
+    sealed trait Type extends Info
+
+    type Mandatory = Empty with Name with Mode with Type
+  }
+
+  case class SubscriptionBuilder[I <: Info] protected (
+      _name: Name = Name(""),
+      _type: Type = Type.Exclusive,
+      _mode: Mode = Mode.Durable
+  ) {
+    def withName(name: Name): SubscriptionBuilder[I with Info.Name] =
+      this.copy(_name = Name(s"${name.value}-subscription"))
+
+    def withMode(mode: Mode): SubscriptionBuilder[I with Info.Mode] =
+      this.copy(_mode = mode)
+
+    def withType(typ: Type): SubscriptionBuilder[I with Info.Type] =
+      this.copy(_type = typ)
+
+    /**
+      * It creates a subscription with default configuration.
+      *
+      * - type: Exclusive
+      * - mode: Durable
+      */
+    def build(
+        implicit @implicitNotFound(
+          "Subscription.Name is mandatory. By default Type=Exclusive and Mode=Durable."
+        ) ev: I =:= Info.Mandatory
+    ): Subscription =
+      new Subscription {
+        val name   = _name
+        val `type` = _type
+        val mode   = _mode
+      }
+
   }
 
-  /**
-    * It creates a subscription with default configuration.
-    *
-    * - type: Exclusive
-    * - mode: Durable
-    */
-  def apply(name: Name): Subscription =
-    // Same as Java's defaults: https://github.com/apache/pulsar/blob/master/pulsar-client/src/main/java/org/apache/pulsar/client/impl/conf/ConsumerConfigurationData.java#L62
-    SubscriptionImpl(Name(s"${name.value}-subscription"), Type.Exclusive, Mode.Durable)
+  object Builder extends SubscriptionBuilder[Info.Empty with Info.Type with Info.Mode]()
 
 }