Error when using JsonMessageSerializer with default settings #252

Signed-off-by: Tomasz Maruszak <maruszaktomasz@gmail.com>

src/Host.Plugin.Properties.xml

@@ -4,7 +4,7 @@
 	<Import Project="Common.NuGet.Properties.xml" />
 
 	<PropertyGroup>
-    <Version>2.3.2</Version>
+    <Version>2.3.3</Version>
   </PropertyGroup>
 
 </Project>

src/SlimMessageBus.Host.Serialization.SystemTextJson/JsonMessageSerializer.cs

@@ -15,13 +15,19 @@ public class JsonMessageSerializer : IMessageSerializer
 
     public JsonMessageSerializer(JsonSerializerOptions options = null)
     {
-        Options = options ?? new(JsonSerializerDefaults.Web)
+        Options = options ?? CreateDefaultOptions();
+    }
+
+    public virtual JsonSerializerOptions CreateDefaultOptions()
+    {
+        var options = new JsonSerializerOptions(JsonSerializerDefaults.Web)
         {
             WriteIndented = false,
             DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
             AllowTrailingCommas = true
         };
-        Options.Converters.Add(new ObjectToInferredTypesConverter());
+        options.Converters.Add(new ObjectToInferredTypesConverter());
+        return options;
     }
 
     public byte[] Serialize(Type t, object message) =>

src/SlimMessageBus.Host.Serialization.SystemTextJson/SerializationBuilderExtensions.cs

@@ -17,7 +17,8 @@ public static class SerializationBuilderExtensions
     public static TBuilder AddJsonSerializer<TBuilder>(this TBuilder builder, JsonSerializerOptions options = null)
         where TBuilder : ISerializationBuilder
     {
-        builder.RegisterSerializer<JsonMessageSerializer>(services => {
+        builder.RegisterSerializer<JsonMessageSerializer>(services =>
+        {
             services.TryAddSingleton(svp => new JsonMessageSerializer(options ?? svp.GetService<JsonSerializerOptions>()));
         });
         return builder;

src/Tests/SlimMessageBus.Host.Serialization.SystemTextJson.Test/JsonMessageSerializerTests.cs

@@ -1,6 +1,5 @@
 namespace SlimMessageBus.Host.Serialization.SystemTextJson.Test;
 
-using FluentAssertions;
 
 public class JsonMessageSerializerTests
 {
@@ -29,4 +28,49 @@ public void When_SerializeAndDeserialize_Given_TypeObject_Then_TriesToInferPrimi
         // assert
         deserializedValue.Should().Be(expectedValue);
     }
-}
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void When_RegisterSerializer_Then_UsesOptionsFromContainerIfAvailable(bool jsonOptionComeFromContainer)
+    {
+        // arrange
+        var mbb = MessageBusBuilder.Create();
+        mbb.AddJsonSerializer();
+
+        var services = new ServiceCollection();
+
+        var jsonOptions = new JsonSerializerOptions();
+
+        // Simulate the options have been used in an serializer already (see https://github.com/zarusz/SlimMessageBus/issues/252)
+        // Modifying options (adding converters) when the options are already in use by a serializer will throw an exception: System.InvalidOperationException : This JsonSerializerOptions instance is read-only or has already been used in serialization or deserialization.
+        JsonSerializer.SerializeToUtf8Bytes(new Dictionary<string, object>(), typeof(Dictionary<string, object>), jsonOptions);
+
+        if (jsonOptionComeFromContainer)
+        {
+            services.AddSingleton(jsonOptions);
+        }
+
+        foreach (var action in mbb.PostConfigurationActions)
+        {
+            action(services);
+        }
+
+        var serviceProvider = services.BuildServiceProvider();
+
+        var subject = serviceProvider.GetRequiredService<JsonMessageSerializer>();
+
+        // act
+        if (jsonOptionComeFromContainer)
+        {
+            subject.Options.Should().BeSameAs(jsonOptions);
+        }
+        else
+        {
+            subject.Options.Should().NotBeSameAs(jsonOptions);
+        }
+
+        // assert
+        serviceProvider.GetService<IMessageSerializer>().Should().BeSameAs(subject);
+    }
+}

src/Tests/SlimMessageBus.Host.Serialization.SystemTextJson.Test/Usings.cs

@@ -1,3 +1,5 @@
+global using System.Text.Json;
+
 global using FluentAssertions;
 
 global using Microsoft.Extensions.DependencyInjection;