Use JSON polymorphism with RC2 nightly.

Directory.Packages.props

@@ -15,15 +15,15 @@
     <PackageVersion Include="JustEat.HttpClientInterception" Version="4.3.0" />
     <PackageVersion Include="MartinCostello.Logging.XUnit" Version="0.4.0" />
     <PackageVersion Include="MartinCostello.Testing.AwsLambdaTestServer" Version="0.8.0" />
-    <PackageVersion Include="Microsoft.AspNetCore.WebUtilities" Version="9.0.0-rc.1.24452.1" />
-    <PackageVersion Include="Microsoft.Extensions.Configuration.Binder" Version="9.0.0-rc.1.24431.7" />
-    <PackageVersion Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="9.0.0-rc.1.24431.7" />
-    <PackageVersion Include="Microsoft.Extensions.Configuration.Json" Version="9.0.0-rc.1.24431.7" />
-    <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="9.0.0-rc.1.24431.7" />
-    <PackageVersion Include="Microsoft.Extensions.Http" Version="9.0.0-rc.1.24431.7" />
+    <PackageVersion Include="Microsoft.AspNetCore.WebUtilities" Version="9.0.0-rc.2.24462.10" />
+    <PackageVersion Include="Microsoft.Extensions.Configuration.Binder" Version="9.0.0-rc.2.24462.5" />
+    <PackageVersion Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="9.0.0-rc.2.24462.5" />
+    <PackageVersion Include="Microsoft.Extensions.Configuration.Json" Version="9.0.0-rc.2.24462.5" />
+    <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="9.0.0-rc.2.24462.5" />
+    <PackageVersion Include="Microsoft.Extensions.Http" Version="9.0.0-rc.2.24462.5" />
     <PackageVersion Include="Microsoft.Extensions.Http.Diagnostics" Version="9.0.0-preview.8.24460.1" />
     <PackageVersion Include="Microsoft.Extensions.Http.Resilience" Version="9.0.0-preview.8.24460.1" />
-    <PackageVersion Include="Microsoft.Extensions.Logging.Console" Version="9.0.0-rc.1.24431.7" />
+    <PackageVersion Include="Microsoft.Extensions.Logging.Console" Version="9.0.0-rc.2.24462.5" />
     <PackageVersion Include="Microsoft.Extensions.Telemetry" Version="9.0.0-preview.8.24460.1" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
@@ -38,7 +38,7 @@
     <PackageVersion Include="ReportGenerator" Version="5.3.9" />
     <PackageVersion Include="Shouldly" Version="4.2.1" />
     <PackageVersion Include="System.Private.Uri" Version="4.3.2" />
-    <PackageVersion Include="System.Text.Json" Version="9.0.0-rc.1.24431.7" />
+    <PackageVersion Include="System.Text.Json" Version="9.0.0-rc.2.24462.5" />
     <PackageVersion Include="xRetry" Version="1.9.0" />
     <PackageVersion Include="xunit" Version="2.9.0" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.8.2" />

NuGet.config

@@ -2,9 +2,13 @@
 <configuration>
   <packageSources>
     <clear />
+    <add key="dotnet9" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet9/nuget/v3/index.json" />
     <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
   </packageSources>
   <packageSourceMapping>
+    <packageSource key="dotnet9">
+      <package pattern="*" />
+    </packageSource>
     <packageSource key="NuGet">
       <package pattern="*" />
     </packageSource>

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "9.0.100-rc.1.24452.12",
+    "version": "9.0.100-rc.2.24463.1",
     "allowPrerelease": false,
     "rollForward": "latestMajor"
   },

src/LondonTravel.Skill/AlexaSkill.cs

@@ -26,7 +26,7 @@ internal sealed class AlexaSkill(
     /// <returns>
     /// The <see cref="ResponseBody"/> to return from the skill.
     /// </returns>
-    public SkillResponse OnError(ISystemExceptionRequest error, Session session)
+    public SkillResponse OnError(SystemExceptionRequest error, Session session)
     {
         Log.SystemError(
             logger,
@@ -67,7 +67,7 @@ public SkillResponse OnError(Exception? exception, Session session, string reque
     /// A <see cref="Task{TResult}"/> representing the asynchronous operation
     /// which returns the <see cref="ResponseBody"/> to return from the skill.
     /// </returns>
-    public async Task<SkillResponse> OnIntentAsync(IIntentRequest intent, Session session)
+    public async Task<SkillResponse> OnIntentAsync(IntentRequest intent, Session session)
     {
         var handler = intentFactory.Create(intent.Intent);
         return await handler.RespondAsync(intent.Intent, session);

src/LondonTravel.Skill/AppJsonSerializerContext.cs

@@ -19,5 +19,5 @@ namespace MartinCostello.LondonTravel.Skill;
 [JsonSerializable(typeof(SkillResponse))]
 [JsonSerializable(typeof(SkillUserPreferences))]
 [JsonSerializable(typeof(StandardCard))]
-[JsonSourceGenerationOptions(PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase)]
+[JsonSourceGenerationOptions(AllowOutOfOrderMetadataProperties = true, PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase)]
 public sealed partial class AppJsonSerializerContext : JsonSerializerContext;

src/LondonTravel.Skill/FunctionHandler.cs

@@ -49,12 +49,12 @@ private async Task<SkillResponse> HandleRequestAsync(SkillRequest request)
     {
         try
         {
-            return request.Request.Type switch
+            return request.Request switch
             {
-                RequestTypes.Intent => await skill.OnIntentAsync(request.Request, request.Session),
-                RequestTypes.Launch => skill.OnLaunch(request.Session),
-                RequestTypes.SessionEnded => skill.OnSessionEnded(request.Session),
-                RequestTypes.SystemException => skill.OnError(request.Request, request.Session),
+                IntentRequest intent => await skill.OnIntentAsync(intent, request.Session),
+                LaunchRequest => skill.OnLaunch(request.Session),
+                SessionEndedRequest => skill.OnSessionEnded(request.Session),
+                SystemExceptionRequest exception => skill.OnError(exception, request.Session),
                 _ => skill.OnError(null, request.Session, request.Request.Type),
             };
         }

src/LondonTravel.Skill/Models/IntentRequest.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Martin Costello, 2017. All rights reserved.
+// Licensed under the Apache 2.0 license. See the LICENSE file in the project root for full license information.
+
+using System.Text.Json.Serialization;
+
+namespace MartinCostello.LondonTravel.Skill.Models;
+
+public sealed class IntentRequest : Request
+{
+    [JsonIgnore]
+    public override string Type => "IntentRequest";
+
+    [JsonPropertyName("dialogState")]
+    public string DialogState { get; set; } = default!;
+
+    [JsonPropertyName("intent")]
+    public Intent Intent { get; set; } = default!;
+}

src/LondonTravel.Skill/Models/IIntentRequest.cs → src/LondonTravel.Skill/Models/LaunchRequest.cs

@@ -1,11 +1,12 @@
 // Copyright (c) Martin Costello, 2017. All rights reserved.
 // Licensed under the Apache 2.0 license. See the LICENSE file in the project root for full license information.
 
+using System.Text.Json.Serialization;
+
 namespace MartinCostello.LondonTravel.Skill.Models;
 
-internal interface IIntentRequest : IRequest
+public sealed class LaunchRequest : Request
 {
-    string DialogState { get; }
-
-    Intent Intent { get; }
+    [JsonIgnore]
+    public override string Type => "LaunchRequest";
 }

src/LondonTravel.Skill/Models/Request.cs

@@ -5,11 +5,15 @@
 
 namespace MartinCostello.LondonTravel.Skill.Models;
 
-public sealed class Request : IRequest, IIntentRequest, ISessionEndedRequest, ISystemExceptionRequest
+[JsonDerivedType(typeof(IntentRequest), RequestTypes.Intent)]
+[JsonDerivedType(typeof(LaunchRequest), RequestTypes.Launch)]
+[JsonDerivedType(typeof(SessionEndedRequest), RequestTypes.SessionEnded)]
+[JsonDerivedType(typeof(SystemExceptionRequest), RequestTypes.SystemException)]
+[JsonPolymorphic(TypeDiscriminatorPropertyName = "type")]
+public abstract class Request
 {
-    [JsonPropertyName("type")]
-    [JsonRequired]
-    public string Type { get; set; } = default!;
+    [JsonIgnore]
+    public abstract string Type { get; }
 
     [JsonPropertyName("requestId")]
     public string RequestId { get; set; } = default!;
@@ -20,29 +24,4 @@ public sealed class Request : IRequest, IIntentRequest, ISessionEndedRequest, IS
     [JsonConverter(typeof(MixedDateTimeConverter))]
     [JsonPropertyName("timestamp")]
     public DateTime Timestamp { get; set; }
-
-    //// Properties for "IntentRequest"
-
-    [JsonPropertyName("dialogState")]
-    public string DialogState { get; set; } = default!;
-
-    [JsonPropertyName("intent")]
-    public Intent Intent { get; set; } = default!;
-
-    //// Properties for "SessionEndedRequest"
-
-    [JsonConverter(typeof(JsonStringEnumConverter<Reason>))]
-    [JsonPropertyName("reason")]
-    public Reason Reason { get; set; }
-
-    //// Properties for "System.ExceptionEncountered"
-
-    [JsonPropertyName("cause")]
-    public AlexaErrorCause ErrorCause { get; set; } = default!;
-
-    //// Properties for "SessionEndedRequest" and "System.ExceptionEncountered"
-
-    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
-    [JsonPropertyName("error")]
-    public AlexaError Error { get; set; } = default!;
 }

src/LondonTravel.Skill/Models/SessionEndedRequest.cs

@@ -0,0 +1,20 @@
+// Copyright (c) Martin Costello, 2017. All rights reserved.
+// Licensed under the Apache 2.0 license. See the LICENSE file in the project root for full license information.
+
+using System.Text.Json.Serialization;
+
+namespace MartinCostello.LondonTravel.Skill.Models;
+
+public sealed class SessionEndedRequest : Request
+{
+    [JsonIgnore]
+    public override string Type => "SessionEndedRequest";
+
+    [JsonConverter(typeof(JsonStringEnumConverter<Reason>))]
+    [JsonPropertyName("reason")]
+    public Reason Reason { get; set; }
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("error")]
+    public AlexaError Error { get; set; } = default!;
+}

src/LondonTravel.Skill/Models/SystemExceptionRequest.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Martin Costello, 2017. All rights reserved.
+// Licensed under the Apache 2.0 license. See the LICENSE file in the project root for full license information.
+
+using System.Text.Json.Serialization;
+
+namespace MartinCostello.LondonTravel.Skill.Models;
+
+public sealed class SystemExceptionRequest : Request
+{
+    [JsonIgnore]
+    public override string Type => "System.ExceptionEncountered";
+
+    [JsonPropertyName("cause")]
+    public AlexaErrorCause ErrorCause { get; set; } = default!;
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("error")]
+    public AlexaError Error { get; set; } = default!;
+}

test/LondonTravel.Skill.NativeAotTests/EndToEndTests.cs

@@ -132,7 +132,7 @@ public async Task Alexa_Function_Can_Process_Intent_Request_For_Line_Status()
     public async Task Alexa_Function_Can_Process_Launch_Request()
     {
         // Arrange
-        var request = CreateRequest("LaunchRequest");
+        var request = CreateRequest<LaunchRequest>();
 
         // Act
         var actual = await ProcessRequestAsync(request);
@@ -153,7 +153,7 @@ public async Task Alexa_Function_Can_Process_Launch_Request()
     public async Task Alexa_Function_Can_Process_Session_Ended_Request()
     {
         // Arrange
-        var session = new Request()
+        var session = new SessionEndedRequest()
         {
             Reason = Reason.ExceededMaxReprompts,
             Error = new()
@@ -163,7 +163,7 @@ public async Task Alexa_Function_Can_Process_Session_Ended_Request()
             },
         };
 
-        var request = CreateRequest("SessionEndedRequest", session);
+        var request = CreateRequest(session);
 
         // Act
         var actual = await ProcessRequestAsync(request);
@@ -184,7 +184,7 @@ public async Task Alexa_Function_Can_Process_Session_Ended_Request()
     public async Task Alexa_Function_Can_Process_System_Exception_Request()
     {
         // Arrange
-        var exception = new Request()
+        var exception = new SystemExceptionRequest()
         {
             Error = new()
             {
@@ -197,7 +197,7 @@ public async Task Alexa_Function_Can_Process_System_Exception_Request()
             },
         };
 
-        var request = CreateRequest("System.ExceptionEncountered", exception);
+        var request = CreateRequest(exception);
 
         // Act
         var actual = await ProcessRequestAsync(request);
@@ -215,7 +215,7 @@ public async Task Alexa_Function_Can_Process_System_Exception_Request()
 
     private static SkillRequest CreateIntentRequest(string name, params Slot[] slots)
     {
-        var request = new Request()
+        var request = new IntentRequest()
         {
             Intent = new Intent()
             {
@@ -233,10 +233,11 @@ private static SkillRequest CreateIntentRequest(string name, params Slot[] slots
             }
         }
 
-        return CreateRequest("IntentRequest", request);
+        return CreateRequest(request);
     }
 
-    private static SkillRequest CreateRequest(string type, Request? request = null)
+    private static SkillRequest CreateRequest<T>(T? request = null)
+        where T : Request, new()
     {
         var application = new Application()
         {
@@ -265,7 +266,7 @@ private static SkillRequest CreateRequest(string type, Request? request = null)
                     User = user,
                 },
             },
-            Request = request ?? new(),
+            Request = request ?? new T(),
             Session = new()
             {
                 Application = application,
@@ -276,7 +277,6 @@ private static SkillRequest CreateRequest(string type, Request? request = null)
             Version = "1.0",
         };
 
-        result.Request.Type = type;
         result.Request.Locale = "en-GB";
 
         return result;

test/LondonTravel.Skill.Tests/AlexaFunctionTests.cs

@@ -58,7 +58,7 @@ public async Task Cannot_Invoke_Function_With_System_Failure()
         var function = await CreateFunctionAsync();
         var context = new TestLambdaContext();
 
-        var error = new Request()
+        var error = new SystemExceptionRequest()
         {
             Error = new()
             {
@@ -71,7 +71,7 @@ public async Task Cannot_Invoke_Function_With_System_Failure()
             },
         };
 
-        var request = CreateRequest("System.ExceptionEncountered", error);
+        var request = CreateRequest(error);
 
         // Act
         var actual = await function.HandlerAsync(request, context);