Serialization: built-in serializers declare their ids in code (#8676, part 1)

src/contrib/cluster/Akka.Cluster.Metrics/Serialization/ClusterMetricsMessageSerializer.cs

@@ -44,6 +44,12 @@ public ClusterMetricsMessageSerializer(ExtendedActorSystem system)
             _serialization = new Lazy<Akka.Serialization.Serialization>(() => new Akka.Serialization.Serialization(system));
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterMetricsMessageSerializer) ? 10 : base.Identifier;
+
         /// <inheritdoc />
         public override byte[] ToBinary(object obj)
         {

src/contrib/cluster/Akka.Cluster.Sharding/Serialization/ClusterShardingMessageSerializer.cs

@@ -148,6 +148,12 @@ public ClusterShardingMessageSerializer(ExtendedActorSystem system) : base(syste
             };
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterShardingMessageSerializer) ? 13 : base.Identifier;
+
         private ShardingEnvelope ShardingEnvelopeFromBinary(byte[] bytes)
         {
             var proto = Proto.Msg.ShardingEnvelope.Parser.ParseFrom(bytes);

src/contrib/cluster/Akka.Cluster.Tools/Client/Serialization/ClusterClientMessageSerializer.cs

@@ -48,6 +48,12 @@ public ClusterClientMessageSerializer(ExtendedActorSystem system) : base(system)
             _payloadSupport = new WrappedPayloadSupport(system);
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterClientMessageSerializer) ? 15 : base.Identifier;
+
         /// <summary>
         /// Serializes the given object into a byte array
         /// </summary>

src/contrib/cluster/Akka.Cluster.Tools/PublishSubscribe/Serialization/DistributedPubSubMessageSerializer.cs

@@ -55,6 +55,12 @@ public DistributedPubSubMessageSerializer(ExtendedActorSystem system) : base(sys
             };
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(DistributedPubSubMessageSerializer) ? 9 : base.Identifier;
+
         /// <summary>
         /// Serializes the given object into a byte array
         /// </summary>

src/contrib/cluster/Akka.Cluster.Tools/Singleton/Serialization/ClusterSingletonMessageSerializer.cs

@@ -41,6 +41,12 @@ public ClusterSingletonMessageSerializer(ExtendedActorSystem system) : base(syst
             };
         }
 
+        /// <inheritdoc />
+        /// <remarks>
+        /// A subclass keeps resolving its own id from HOCON via <see cref="Serializer.Identifier"/>.
+        /// </remarks>
+        public override int Identifier => GetType() == typeof(ClusterSingletonMessageSerializer) ? 14 : base.Identifier;
+
         /// <summary>
         /// Serializes the given object into a byte array
         /// </summary>

src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatedDataSerializer.cs

@@ -75,6 +75,8 @@ public ReplicatedDataSerializer(ExtendedActorSystem system) : base(system)
                 system.Settings.Config.GetBoolean("akka.cluster.sharding.distributed-data.backward-compatible-wire-format");
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 11;
 
         public override byte[] ToBinary(object obj)
         {

src/contrib/cluster/Akka.DistributedData/Serialization/ReplicatorMessageSerializer.cs

@@ -168,6 +168,9 @@ public ReplicatorMessageSerializer(Akka.Actor.ExtendedActorSystem system) : base
             });
         }
 
+        /// <inheritdoc />
+        public override int Identifier => 12;
+
         public override string Manifest(object o)
         {
             switch (o)

src/core/Akka.API.Tests/BuiltInSerializerIdentifierSpec.cs

@@ -0,0 +1,66 @@
+//-----------------------------------------------------------------------
+// <copyright file="BuiltInSerializerIdentifierSpec.cs" company="Akka.NET Project">
+//     Copyright (C) 2009-2025 Lightbend Inc. <http://www.lightbend.com>
+//     Copyright (C) 2013-2025 .NET Foundation <https://github.com/akkadotnet/akka.net>
+// </copyright>
+//-----------------------------------------------------------------------
+
+using System;
+using System.Runtime.CompilerServices;
+using Akka.Actor;
+using Akka.Cluster.Metrics;
+using Akka.Cluster.Sharding;
+using Akka.Cluster.Tools.Client;
+using Akka.Cluster.Tools.PublishSubscribe;
+using Akka.Cluster.Tools.Singleton;
+using Akka.Configuration;
+using Akka.Serialization;
+using Akka.Streams;
+using Xunit;
+using DistributedDataExtension = Akka.DistributedData.DistributedData;
+using PersistenceExtension = Akka.Persistence.Persistence;
+
+namespace Akka.API.Tests
+{
+    /// <summary>
+    /// Every built-in serializer now declares its wire id in code. This is the one project that references all of
+    /// Remote, Cluster, Cluster.Tools, Cluster.Sharding, DistributedData, Cluster.Metrics, Persistence, Streams and
+    /// core, so it's the one place that can check every built-in serializer's code <see cref="Serializer.Identifier"/>
+    /// against every module's shipped <c>akka.actor.serialization-identifiers</c> row in a single test.
+    ///
+    /// Each serializer is created with <see cref="RuntimeHelpers.GetUninitializedObject"/>, which skips the
+    /// constructor entirely, leaving the instance's actor-system field null. A built-in serializer's <c>Identifier</c>
+    /// is either a hardcoded constant or a <c>GetType()</c> guard around one - never a HOCON read - so this is safe
+    /// for all of them. It also proves D1: a serializer that still resolved its id lazily from HOCON would touch the
+    /// null actor-system field on first access and throw, instead of quietly returning the right answer.
+    /// </summary>
+    public class BuiltInSerializerIdentifierSpec
+    {
+        [Fact(DisplayName = "Should_match_HOCON_serialization_identifiers_When_reading_every_builtin_serializer_Identifier")]
+        public void Should_match_HOCON_serialization_identifiers_When_reading_every_builtin_serializer_Identifier()
+        {
+            var config = ConfigurationFactory.FromResource<Remote.RemoteSettings>("Akka.Remote.Configuration.Remote.conf")
+                .WithFallback(ConfigurationFactory.FromResource<Cluster.ClusterSettings>("Akka.Cluster.Configuration.Cluster.conf"))
+                .WithFallback(ClusterSharding.DefaultConfig())
+                .WithFallback(ClusterSingleton.DefaultConfig())
+                .WithFallback(DistributedPubSub.DefaultConfig())
+                .WithFallback(ClusterClientReceptionist.DefaultConfig())
+                .WithFallback(DistributedDataExtension.DefaultConfig())
+                .WithFallback(ClusterMetrics.DefaultConfig())
+                .WithFallback(PersistenceExtension.DefaultConfig())
+                .WithFallback(ActorMaterializer.DefaultConfig());
+
+            // config only: no ActorSystem needed to read the rows
+            var rows = config.WithFallback(ConfigurationFactory.Default()).GetConfig("akka.actor.serialization-identifiers");
+            foreach (var row in rows.AsEnumerable())
+            {
+                var type = Type.GetType(row.Key, throwOnError: true);
+                var expectedId = row.Value.GetInt();
+
+                var serializer = (Serializer)RuntimeHelpers.GetUninitializedObject(type);
+                Assert.True(expectedId == serializer.Identifier,
+                    $"{type.FullName} declared Identifier {serializer.Identifier}, but its HOCON row says {expectedId}");
+            }
+        }
+    }
+}

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.DotNet.verified.txt

@@ -447,6 +447,7 @@ namespace Akka.Cluster.Serialization
     public class ClusterMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCluster.Net.verified.txt

@@ -447,6 +447,7 @@ namespace Akka.Cluster.Serialization
     public class ClusterMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.DotNet.verified.txt

@@ -280,6 +280,7 @@ namespace Akka.Cluster.Metrics.Serialization
     public class ClusterMetricsMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMetricsMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterMetrics.Net.verified.txt

@@ -280,6 +280,7 @@ namespace Akka.Cluster.Metrics.Serialization
     public class ClusterMetricsMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterMetricsMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.DotNet.verified.txt

@@ -581,6 +581,7 @@ namespace Akka.Cluster.Sharding.Serialization
     public class ClusterShardingMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterShardingMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.Net.verified.txt

@@ -581,6 +581,7 @@ namespace Akka.Cluster.Sharding.Serialization
     public class ClusterShardingMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterShardingMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.DotNet.verified.txt

@@ -214,6 +214,7 @@ namespace Akka.Cluster.Tools.Client.Serialization
     public class ClusterClientMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterClientMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -423,6 +424,7 @@ namespace Akka.Cluster.Tools.PublishSubscribe.Serialization
     public class DistributedPubSubMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public DistributedPubSubMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -584,6 +586,7 @@ namespace Akka.Cluster.Tools.Singleton.Serialization
     public class ClusterSingletonMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterSingletonMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterTools.Net.verified.txt

@@ -214,6 +214,7 @@ namespace Akka.Cluster.Tools.Client.Serialization
     public class ClusterClientMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterClientMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -423,6 +424,7 @@ namespace Akka.Cluster.Tools.PublishSubscribe.Serialization
     public class DistributedPubSubMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public DistributedPubSubMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
@@ -584,6 +586,7 @@ namespace Akka.Cluster.Tools.Singleton.Serialization
     public class ClusterSingletonMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ClusterSingletonMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.DotNet.verified.txt

@@ -5158,6 +5158,7 @@ namespace Akka.Serialization
     public class ByteArraySerializer : Akka.Serialization.SerializerV2
     {
         public ByteArraySerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object Deserialize(System.Buffers.ReadOnlySequence<byte> bytes, string manifest) { }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override object FromBinary(byte[] bytes, string manifest) { }
@@ -5183,6 +5184,7 @@ namespace Akka.Serialization
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Configuration.Config config) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Serialization.NewtonSoftJsonSerializerSettings settings) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public object Serializer { get; }
         public Newtonsoft.Json.JsonSerializerSettings Settings { get; }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveCore.Net.verified.txt

@@ -5147,6 +5147,7 @@ namespace Akka.Serialization
     public class ByteArraySerializer : Akka.Serialization.SerializerV2
     {
         public ByteArraySerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object Deserialize(System.Buffers.ReadOnlySequence<byte> bytes, string manifest) { }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override object FromBinary(byte[] bytes, string manifest) { }
@@ -5172,6 +5173,7 @@ namespace Akka.Serialization
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Configuration.Config config) { }
         public NewtonSoftJsonSerializer(Akka.Actor.ExtendedActorSystem system, Akka.Serialization.NewtonSoftJsonSerializerSettings settings) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public object Serializer { get; }
         public Newtonsoft.Json.JsonSerializerSettings Settings { get; }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.DotNet.verified.txt

@@ -1122,13 +1122,15 @@ namespace Akka.DistributedData.Serialization
     public sealed class ReplicatedDataSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatedDataSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
     }
     public sealed class ReplicatorMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatorMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveDistributedData.Net.verified.txt

@@ -1122,13 +1122,15 @@ namespace Akka.DistributedData.Serialization
     public sealed class ReplicatedDataSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatedDataSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }
     }
     public sealed class ReplicatorMessageSerializer : Akka.Serialization.SerializerWithStringManifest
     {
         public ReplicatorMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override object FromBinary(byte[] bytes, string manifest) { }
         public override string Manifest(object o) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.DotNet.verified.txt

@@ -1256,13 +1256,15 @@ namespace Akka.Persistence.Serialization
     public sealed class PersistenceMessageSerializer : Akka.Serialization.Serializer
     {
         public PersistenceMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
     }
     public class PersistenceSnapshotSerializer : Akka.Serialization.Serializer
     {
         public PersistenceSnapshotSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApprovePersistence.Net.verified.txt

@@ -1256,13 +1256,15 @@ namespace Akka.Persistence.Serialization
     public sealed class PersistenceMessageSerializer : Akka.Serialization.Serializer
     {
         public PersistenceMessageSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }
     }
     public class PersistenceSnapshotSerializer : Akka.Serialization.Serializer
     {
         public PersistenceSnapshotSerializer(Akka.Actor.ExtendedActorSystem system) { }
+        public override int Identifier { get; }
         public override bool IncludeManifest { get; }
         public override object FromBinary(byte[] bytes, System.Type type) { }
         public override byte[] ToBinary(object obj) { }