Remove polymorphism

Remove polymorphism as it is not supported when the type discriminator is not the first property in the JSON document.
See dotnet/runtime#72604.

src/LondonTravel.Skill/AppJsonSerializerContext.cs

@@ -14,9 +14,7 @@ namespace MartinCostello.LondonTravel.Skill;
 [ExcludeFromCodeCoverage]
 [JsonSerializable(typeof(IList<Line>))]
 [JsonSerializable(typeof(IList<ServiceDisruption>))]
-[JsonSerializable(typeof(IntentRequest))]
 [JsonSerializable(typeof(LinkAccountCard))]
-[JsonSerializable(typeof(LaunchRequest))]
 [JsonSerializable(typeof(SkillRequest))]
 [JsonSerializable(typeof(SkillResponse))]
 [JsonSerializable(typeof(SkillUserPreferences))]

src/LondonTravel.Skill/Models/Request.cs

@@ -7,15 +7,11 @@ namespace MartinCostello.LondonTravel.Skill.Models;
 
 #pragma warning disable CA1724
 
-[JsonDerivedType(typeof(IntentRequest), "IntentRequest")]
-[JsonDerivedType(typeof(LaunchRequest), "LaunchRequest")]
-[JsonDerivedType(typeof(SessionEndedRequest), "SessionEndedRequest")]
-[JsonDerivedType(typeof(SystemExceptionRequest), "System.ExceptionEncountered")]
-[JsonPolymorphic(TypeDiscriminatorPropertyName = "type")]
-public class Request
+public sealed class Request
 {
-    [JsonIgnore]
-    public virtual string Type { get; }
+    [JsonPropertyName("type")]
+    [JsonRequired]
+    public string Type { get; set; }
 
     [JsonPropertyName("requestId")]
     public string RequestId { get; set; }
@@ -26,4 +22,29 @@ public class Request
     [JsonConverter(typeof(MixedDateTimeConverter))]
     [JsonPropertyName("timestamp")]
     public DateTime Timestamp { get; set; }
+
+    //// Properties for "IntentRequest"
+
+    [JsonPropertyName("dialogState")]
+    public string DialogState { get; set; }
+
+    [JsonPropertyName("intent")]
+    public Intent Intent { get; set; }
+
+    //// Properties for "SessionEndedRequest"
+
+    [JsonConverter(typeof(CustomStringEnumConverter<Reason>))]
+    [JsonPropertyName("reason")]
+    public Reason Reason { get; set; }
+
+    //// Properties for "System.ExceptionEncountered"
+
+    [JsonPropertyName("cause")]
+    public AlexaErrorCause ErrorCause { get; set; }
+
+    //// Properties for "SessionEndedRequest" and "System.ExceptionEncountered"
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("error")]
+    public AlexaError Error { get; set; }
 }

src/LondonTravel.Skill/SkillRequestExtensions.cs

@@ -12,12 +12,12 @@ public static SkillRequest FromModel(this Models.SkillRequest request)
     {
         var result = MapRequest(request);
 
-        result.Request = request.Request switch
+        result.Request = request.Request.Type switch
         {
-            Models.IntentRequest intent => MapIntent(intent),
-            Models.LaunchRequest => new LaunchRequest(),
-            Models.SessionEndedRequest session => MapSessionEnd(session),
-            Models.SystemExceptionRequest exception => MapException(exception),
+            "IntentRequest" => MapIntent(request.Request),
+            "LaunchRequest" => new LaunchRequest(),
+            "SessionEndedRequest" => MapSessionEnd(request.Request),
+            "System.ExceptionEncountered" => MapException(request.Request),
             _ => new UnknownRequest(),
         };
 
@@ -106,7 +106,7 @@ private static SkillRequest MapRequest(Models.SkillRequest request)
         return result;
     }
 
-    private static SystemExceptionRequest MapException(Models.SystemExceptionRequest exception)
+    private static SystemExceptionRequest MapException(Models.Request exception)
     {
         var result = new SystemExceptionRequest();
 
@@ -127,7 +127,7 @@ private static SystemExceptionRequest MapException(Models.SystemExceptionRequest
         return result;
     }
 
-    private static IntentRequest MapIntent(Models.IntentRequest request)
+    private static IntentRequest MapIntent(Models.Request request)
     {
         var result = new IntentRequest()
         {
@@ -151,7 +151,7 @@ private static IntentRequest MapIntent(Models.IntentRequest request)
         return result;
     }
 
-    private static SessionEndedRequest MapSessionEnd(Models.SessionEndedRequest session)
+    private static SessionEndedRequest MapSessionEnd(Models.Request session)
     {
         var result = new SessionEndedRequest()
         {

test/LondonTravel.Skill.Tests/AlexaFunctionTests.cs

@@ -55,7 +55,7 @@ public async Task Cannot_Invoke_Function_With_System_Failure()
         // Arrange
         AlexaFunction function = await CreateFunctionAsync();
 
-        var error = new SystemExceptionRequest()
+        var error = new Request()
         {
             Error = new()
             {
@@ -68,7 +68,7 @@ public async Task Cannot_Invoke_Function_With_System_Failure()
             },
         };
 
-        var request = CreateRequest(error);
+        var request = CreateRequest("System.ExceptionEncountered", error);
 
         // Act
         SkillResponse actual = await function.HandlerAsync(request);

test/LondonTravel.Skill.Tests/EndToEndTests.cs

@@ -15,12 +15,7 @@ public class EndToEndTests(ITestOutputHelper outputHelper) : FunctionTests(outpu
     public async Task Alexa_Function_Can_Process_Intent_Request()
     {
         // Arrange
-        var intent = new IntentRequest()
-        {
-            Intent = new() { Name = "AMAZON.CancelIntent" },
-        };
-
-        SkillRequest request = CreateRequest(intent);
+        SkillRequest request = CreateIntentRequest("AMAZON.CancelIntent");
 
         // Act
         var actual = await ProcessRequestAsync(request);
@@ -37,7 +32,7 @@ public async Task Alexa_Function_Can_Process_Intent_Request()
     public async Task Alexa_Function_Can_Process_Launch_Request()
     {
         // Arrange
-        SkillRequest request = CreateRequest<LaunchRequest>();
+        SkillRequest request = CreateRequest("LaunchRequest");
 
         // Act
         var actual = await ProcessRequestAsync(request);
@@ -59,7 +54,7 @@ public async Task Alexa_Function_Can_Process_Launch_Request()
     public async Task Alexa_Function_Can_Process_Session_Ended_Request()
     {
         // Arrange
-        var session = new SessionEndedRequest()
+        var session = new Request()
         {
             Reason = Reason.ExceededMaxReprompts,
             Error = new()
@@ -69,7 +64,7 @@ public async Task Alexa_Function_Can_Process_Session_Ended_Request()
             },
         };
 
-        SkillRequest request = CreateRequest(session);
+        SkillRequest request = CreateRequest("SessionEndedRequest", session);
 
         // Act
         var actual = await ProcessRequestAsync(request);
@@ -91,7 +86,7 @@ public async Task Alexa_Function_Can_Process_Session_Ended_Request()
     public async Task Alexa_Function_Can_Process_System_Exception_Request()
     {
         // Arrange
-        var exception = new SystemExceptionRequest()
+        var exception = new Request()
         {
             Error = new()
             {
@@ -104,7 +99,7 @@ public async Task Alexa_Function_Can_Process_System_Exception_Request()
             },
         };
 
-        SkillRequest request = CreateRequest(exception);
+        SkillRequest request = CreateRequest("System.ExceptionEncountered", exception);
 
         // Act
         var actual = await ProcessRequestAsync(request);

test/LondonTravel.Skill.Tests/FunctionTests.cs

@@ -60,7 +60,7 @@ protected virtual async Task<AlexaFunction> CreateFunctionAsync()
 
     protected virtual SkillRequest CreateIntentRequest(string name, params Slot[] slots)
     {
-        var request = new IntentRequest()
+        var request = new Request()
         {
             Intent = new Intent()
             {
@@ -78,11 +78,10 @@ protected virtual SkillRequest CreateIntentRequest(string name, params Slot[] sl
             }
         }
 
-        return CreateRequest(request);
+        return CreateRequest("IntentRequest", request);
     }
 
-    protected virtual SkillRequest CreateRequest<T>(T request = null)
-        where T : Request, new()
+    protected virtual SkillRequest CreateRequest(string type, Request request = null)
     {
         var application = new Application()
         {
@@ -111,7 +110,7 @@ protected virtual SkillRequest CreateRequest<T>(T request = null)
                     User = user,
                 },
             },
-            Request = request ?? new T(),
+            Request = request ?? new(),
             Session = new()
             {
                 Application = application,
@@ -122,6 +121,7 @@ protected virtual SkillRequest CreateRequest<T>(T request = null)
             Version = "1.0",
         };
 
+        result.Request.Type = type;
         result.Request.Locale = "en-GB";
 
         return result;

test/LondonTravel.Skill.Tests/LaunchTests.cs

@@ -14,7 +14,7 @@ public async Task Can_Invoke_Function()
         // Arrange
         AlexaFunction function = await CreateFunctionAsync();
 
-        SkillRequest request = CreateRequest<LaunchRequest>();
+        SkillRequest request = CreateRequest("LaunchRequest");
 
         // Act
         SkillResponse actual = await function.HandlerAsync(request);

test/LondonTravel.Skill.Tests/SerializationTests.cs

@@ -2,18 +2,17 @@
 // Licensed under the Apache 2.0 license. See the LICENSE file in the project root for full license information.
 
 using System.Text.Json;
-using MartinCostello.LondonTravel.Skill.Models;
 
 namespace MartinCostello.LondonTravel.Skill;
 
 public static class SerializationTests
 {
     [Theory]
-    [InlineData("IntentRequest", typeof(IntentRequest))]
-    [InlineData("LaunchRequest", typeof(LaunchRequest))]
-    [InlineData("LaunchRequestWithEpochTimestamp", typeof(LaunchRequest))]
-    [InlineData("SessionEndedRequest", typeof(SessionEndedRequest))]
-    public static async Task Can_Deserialize_Request(string name, Type expectedType)
+    [InlineData("IntentRequest")]
+    [InlineData("LaunchRequest")]
+    [InlineData("LaunchRequestWithEpochTimestamp")]
+    [InlineData("SessionEndedRequest")]
+    public static async Task Can_Deserialize_Request(string name)
     {
         // Arrange
         string json = await File.ReadAllTextAsync(Path.Combine("Samples", $"{name}.json"));
@@ -24,7 +23,6 @@ public static async Task Can_Deserialize_Request(string name, Type expectedType)
         // Assert
         actual.ShouldNotBeNull();
         actual.Request.ShouldNotBeNull();
-        actual.Request.ShouldBeOfType(expectedType);
     }
 
     [Theory]

test/LondonTravel.Skill.Tests/SessionEndedTests.cs

@@ -14,7 +14,7 @@ public async Task Can_Invoke_Function()
         // Arrange
         AlexaFunction function = await CreateFunctionAsync();
 
-        SkillRequest request = CreateRequest<SessionEndedRequest>();
+        SkillRequest request = CreateRequest("SessionEndedRequest");
 
         // Act
         SkillResponse actual = await function.HandlerAsync(request);

test/LondonTravel.Skill.Tests/UnknownIntentTests.cs

@@ -31,9 +31,4 @@ public async Task Can_Invoke_Function()
         var ssml = response.OutputSpeech.ShouldBeOfType<SsmlOutputSpeech>();
         ssml.Ssml.ShouldBe("<speak>Sorry, I don't understand how to do that.</speak>");
     }
-
-    private sealed class UnknownRequest : Request
-    {
-        public override string Type => "Unknown";
-    }
 }

test/LondonTravel.Skill.Tests/UnknownRequestTests.cs

@@ -13,17 +13,12 @@ public async Task Can_Invoke_Function()
         // Arrange
         AlexaFunction function = await CreateFunctionAsync();
 
-        SkillRequest request = CreateRequest<UnknownRequest>();
+        SkillRequest request = CreateRequest("Unknown");
 
         // Act
         SkillResponse actual = await function.HandlerAsync(request);
 
         // Assert
         AssertResponse(actual);
     }
-
-    private sealed class UnknownRequest : Request
-    {
-        public override string Type => "Unknown";
-    }
 }