Use CSharpType rather than Type for serialization hooks (#9166)

For framework types that are generic where the arg may be a
non-framework type, we lose the generic type arg information when using
Type.

Author: JoshLove-msft

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/MrwSerializationTypeDefinition.cs

@@ -1822,44 +1822,49 @@ private MethodBodyStatement CreateValueSerializationStatement(
             SerializationFormat serializationFormat,
             ValueExpression value)
         {
-            // append the `.Value` if needed (when the type is nullable and a value type)
-            value = value.NullableStructValue(type);
-
-            // now we just need to focus on how we serialize a value
-            if (type.IsFrameworkType)
-                return ScmCodeModelGenerator.Instance.TypeFactory.SerializeJsonValue(type.FrameworkType, value, _utf8JsonWriterSnippet, _mrwOptionsParameterSnippet, serializationFormat);
-
-            if (!type.IsEnum)
-                return _utf8JsonWriterSnippet.WriteObjectValue(value.As(type), options: _mrwOptionsParameterSnippet);
-
-            if (type.IsStruct) //is extensible
-            {
-                if (type.UnderlyingEnumType.Equals(typeof(string)))
-                    return _utf8JsonWriterSnippet.WriteStringValue(value.Invoke(nameof(ToString)));
-
-                return _utf8JsonWriterSnippet.WriteNumberValue(value.Invoke($"ToSerial{type.UnderlyingEnumType.Name}"));
-            }
-            else
-            {
-                if (type.UnderlyingEnumType.Equals(typeof(int)))
-                    // when the fixed enum is implemented as int, we cast to the value
-                    return _utf8JsonWriterSnippet.WriteNumberValue(value.CastTo(type.UnderlyingEnumType));
-
-                if (type.UnderlyingEnumType.Equals(typeof(string)))
-                    return _utf8JsonWriterSnippet.WriteStringValue(value.Invoke($"ToSerial{type.UnderlyingEnumType.Name}"));
-
-                return _utf8JsonWriterSnippet.WriteNumberValue(value.Invoke($"ToSerial{type.UnderlyingEnumType.Name}"));
-            }
+            return ScmCodeModelGenerator.Instance.TypeFactory.SerializeJsonValue(type, value, _utf8JsonWriterSnippet, _mrwOptionsParameterSnippet, serializationFormat);
         }
 
         internal static MethodBodyStatement SerializeJsonValueCore(
-            Type valueType,
+            CSharpType valueType,
             ValueExpression value,
             ScopedApi<Utf8JsonWriter> utf8JsonWriter,
             ScopedApi<ModelReaderWriterOptions> mrwOptionsParameter,
             SerializationFormat serializationFormat)
         {
-            MethodBodyStatement? statement = valueType switch
+            // append the `.Value` if needed (when the type is nullable and a value type)
+            value = value.NullableStructValue(valueType);
+
+            // Handle enums
+            if (valueType.IsEnum)
+            {
+                if (valueType.IsStruct) // extensible enum
+                {
+                    if (valueType.UnderlyingEnumType.Equals(typeof(string)))
+                        return utf8JsonWriter.WriteStringValue(value.Invoke(nameof(ToString)));
+
+                    return utf8JsonWriter.WriteNumberValue(value.Invoke($"ToSerial{valueType.UnderlyingEnumType.Name}"));
+                }
+                else // fixed enum
+                {
+                    if (valueType.UnderlyingEnumType.Equals(typeof(int)))
+                        // when the fixed enum is implemented as int, we cast to the value
+                        return utf8JsonWriter.WriteNumberValue(value.CastTo(valueType.UnderlyingEnumType));
+
+                    if (valueType.UnderlyingEnumType.Equals(typeof(string)))
+                        return utf8JsonWriter.WriteStringValue(value.Invoke($"ToSerial{valueType.UnderlyingEnumType.Name}"));
+
+                    return utf8JsonWriter.WriteNumberValue(value.Invoke($"ToSerial{valueType.UnderlyingEnumType.Name}"));
+                }
+            }
+
+            // Handle non-enum types
+            if (!valueType.IsFrameworkType)
+                return utf8JsonWriter.WriteObjectValue(value.As(valueType), options: mrwOptionsParameter);
+
+            // Handle framework types
+            var frameworkType = valueType.FrameworkType;
+            MethodBodyStatement? statement = frameworkType switch
             {
                 var t when t == typeof(JsonElement) =>
                     value.As<JsonElement>().WriteTo(utf8JsonWriter),
@@ -1868,21 +1873,21 @@ var t when ValueTypeIsInt(t) && serializationFormat == SerializationFormat.Int_S
                 var t when ValueTypeIsNumber(t) =>
                     utf8JsonWriter.WriteNumberValue(value),
                 var t when t == typeof(object) =>
-                    utf8JsonWriter.WriteObjectValue(value.As(valueType), mrwOptionsParameter),
+                    utf8JsonWriter.WriteObjectValue(value.As(frameworkType), mrwOptionsParameter),
                 var t when t == typeof(string) || t == typeof(char) || t == typeof(Guid) =>
                     utf8JsonWriter.WriteStringValue(value),
                 var t when t == typeof(bool) =>
                     utf8JsonWriter.WriteBooleanValue(value),
                 var t when t == typeof(byte[]) =>
                     utf8JsonWriter.WriteBase64StringValue(value, serializationFormat.ToFormatSpecifier()),
                 var t when t == typeof(DateTimeOffset) || t == typeof(DateTime) || t == typeof(TimeSpan) =>
-                    SerializeDateTimeRelatedTypes(valueType, serializationFormat, value, utf8JsonWriter, mrwOptionsParameter),
+                    SerializeDateTimeRelatedTypes(frameworkType, serializationFormat, value, utf8JsonWriter, mrwOptionsParameter),
                 var t when t == typeof(IPAddress) =>
                     utf8JsonWriter.WriteStringValue(value.InvokeToString()),
                 var t when t == typeof(Uri) =>
                     utf8JsonWriter.WriteStringValue(new MemberExpression(value, nameof(Uri.AbsoluteUri))),
                 var t when t == typeof(BinaryData) =>
-                    SerializeBinaryData(valueType, serializationFormat, value, utf8JsonWriter),
+                    SerializeBinaryData(frameworkType, serializationFormat, value, utf8JsonWriter),
                 var t when t == typeof(Stream) =>
                     utf8JsonWriter.WriteBinaryData(BinaryDataSnippets.FromStream(value, false)),
                 _ => null
@@ -1894,24 +1899,49 @@ var t when ValueTypeIsNumber(t) =>
                     DiagnosticCodes.UnsupportedSerialization,
                     $"Serialization of type {valueType.Name} is not supported.",
                     severity: EmitterDiagnosticSeverity.Warning);
-
                 return utf8JsonWriter.WriteObjectValue(value.As(valueType), mrwOptionsParameter);
             }
 
             return statement;
         }
 
         internal static ValueExpression DeserializeJsonValueCore(
-            Type valueType,
+            CSharpType valueType,
             ScopedApi<JsonElement> element,
             ScopedApi<BinaryData> data,
             ScopedApi<ModelReaderWriterOptions> mrwOptions,
             SerializationFormat format)
         {
-            ValueExpression? exp = valueType switch
+            // Handle enums
+            if (valueType.IsEnum)
+            {
+                var underlyingValue = DeserializeJsonValueCore(
+                    new CSharpType(valueType.UnderlyingEnumType!),
+                    element,
+                    data,
+                    mrwOptions,
+                    format);
+                return valueType.ToEnum(underlyingValue);
+            }
+
+            // Handle nullable types
+            if (valueType.IsFrameworkType && valueType.FrameworkType == typeof(Nullable<>))
+            {
+                return DeserializeJsonValueCore(valueType.Arguments[0], element, data, mrwOptions, format);
+            }
+
+            // Handle non-framework types
+            if (!valueType.IsFrameworkType)
+            {
+                return GetDeserializationMethodInvocationForType(valueType, element, data, mrwOptions);
+            }
+
+            // Handle framework types
+            var frameworkType = valueType.FrameworkType;
+            ValueExpression? exp = frameworkType switch
             {
                 Type t when t == typeof(Uri) =>
-                    New.Instance(valueType, element.GetString()),
+                    New.Instance(frameworkType, element.GetString()),
                 Type t when t == typeof(IPAddress) =>
                     Static<IPAddress>().Invoke(nameof(IPAddress.Parse), element.GetString()),
                 Type t when t == typeof(BinaryData) =>
@@ -1965,7 +1995,7 @@ Type t when ValueTypeIsInt(t) =>
                     DiagnosticCodes.UnsupportedSerialization,
                     $"Deserialization of type {valueType.Name} is not supported.",
                     severity: EmitterDiagnosticSeverity.Warning);
-                return GetDeserializationMethodInvocationForType(new CSharpType(valueType), element, data, mrwOptions);
+                return GetDeserializationMethodInvocationForType(valueType, element, data, mrwOptions);
             }
 
             return exp;

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/ScmTypeFactory.cs

@@ -230,15 +230,15 @@ private ExtensibleEnumSerializationProvider[] CreateExtensibleEnumSerializations
         }
 
         public virtual ValueExpression DeserializeJsonValue(
-            Type valueType,
+            CSharpType valueType,
             ScopedApi<JsonElement> element,
             ScopedApi<BinaryData> data,
             ScopedApi<ModelReaderWriterOptions> mrwOptionsParameter,
             SerializationFormat format)
             => MrwSerializationTypeDefinition.DeserializeJsonValueCore(valueType, element, data, mrwOptionsParameter, format);
 
         public virtual MethodBodyStatement SerializeJsonValue(
-            Type valueType,
+            CSharpType valueType,
             ValueExpression value,
             ScopedApi<Utf8JsonWriter> utf8JsonWriter,
             ScopedApi<ModelReaderWriterOptions> mrwOptionsParameter,