Support complex properties

Author: Havret

src/System.Text.Json.Protobuf/ProtobufConverter.cs

@@ -21,7 +21,7 @@ public ProtobufConverter()
             {
                 Accessor = fieldDescriptor.Accessor,
                 IsRepeated = fieldDescriptor.IsRepeated,
-                FieldType = GetFieldType(fieldDescriptor.FieldType),
+                FieldType = GetFieldType(fieldDescriptor),
                 JsonName = fieldDescriptor.JsonName,
             };
             _fieldsLookup.Add(fieldDescriptor.JsonName, fieldInfo);
@@ -90,9 +90,9 @@ public override void Write(Utf8JsonWriter writer, T? value, JsonSerializerOption
         writer.WriteEndObject();
     }
 
-    private Type GetFieldType(FieldType fieldType)
+    private Type GetFieldType(FieldDescriptor fieldType)
     {
-        switch (fieldType)
+        switch (fieldType.FieldType)
         {
             case FieldType.Double:
                 return typeof(double);
@@ -116,6 +116,8 @@ private Type GetFieldType(FieldType fieldType)
                 return typeof(bool);
             case FieldType.String:
                 return typeof(string);
+            case FieldType.Message:
+                return fieldType.MessageType.ClrType;
             default:
                 throw new ArgumentOutOfRangeException(nameof(fieldType), $"FieldType: '{fieldType}' is not supported.");
         }

test/System.Text.Json.Protobuf.Tests/MessageWithComplexPropertyTests.Should_serialize_message_with_complex_property.approved.json

@@ -0,0 +1,5 @@
+{
+  "nestedMessage": {
+    "property": "hello"
+  }
+}

test/System.Text.Json.Protobuf.Tests/MessageWithComplexPropertyTests.cs

@@ -0,0 +1,53 @@
+using System.Text.Json.Protobuf.Tests.Utils;
+using Shouldly;
+using SmartAnalyzers.ApprovalTestsExtensions;
+using Xunit;
+
+namespace System.Text.Json.Protobuf.Tests;
+
+public class MessageWithComplexPropertyTests
+{
+    [Fact]
+    public void Should_serialize_message_with_complex_property()
+    {
+        // Arrange
+        var msg = new MessageWithComplexProperty
+        {
+            NestedMessage = new NestedMessage
+            {
+                Property = "hello"
+            }
+        };
+
+        var jsonSerializerOptions = TestHelper.CreateJsonSerializerOptions();
+
+        // Act
+        var serialized = JsonSerializer.Serialize(msg, jsonSerializerOptions);
+
+        // Assert
+        var approver = new ExplicitApprover();
+        approver.VerifyJson(serialized);
+    }
+    
+    [Fact]
+    public void Should_deserialize_message_with_complex_property()
+    {
+        // Arrange
+        var msg = new MessageWithComplexProperty
+        {
+            NestedMessage = new NestedMessage
+            {
+                Property = "hello"
+            }
+        };
+
+        var jsonSerializerOptions = TestHelper.CreateJsonSerializerOptions();
+
+        // Act
+        var serialized = JsonSerializer.Serialize(msg, jsonSerializerOptions);
+        var deserialized = JsonSerializer.Deserialize<MessageWithComplexProperty>(serialized, jsonSerializerOptions);
+
+        // Assert
+        deserialized.ShouldBeEquivalentTo(msg);
+    }
+}

test/System.Text.Json.Protobuf.Tests/Protos/message_with_complex_property.proto

@@ -0,0 +1,11 @@
+syntax = "proto3";
+
+option csharp_namespace = "System.Text.Json.Protobuf.Tests";
+
+message MessageWithComplexProperty {
+  NestedMessage nested_message = 1;
+}
+
+message NestedMessage {
+  string property = 1;
+}