Add ability to proxy the reading and writing of models

sdk/core/System.ClientModel/api/System.ClientModel.net6.0.cs

@@ -255,7 +255,13 @@ public partial class ModelReaderWriterOptions
         public ModelReaderWriterOptions(string format) { }
         public string Format { get { throw null; } }
         public static System.ClientModel.Primitives.ModelReaderWriterOptions Json { get { throw null; } }
+        public object? ProxiedModel { get { throw null; } }
         public static System.ClientModel.Primitives.ModelReaderWriterOptions Xml { get { throw null; } }
+        public void AddProxy<T>(System.ClientModel.Primitives.IPersistableModel<T> proxy) { }
+        public System.ClientModel.Primitives.IJsonModel<T> ResolveProxy<T>(System.ClientModel.Primitives.IJsonModel<T> model) { throw null; }
+        public System.ClientModel.Primitives.IPersistableModel<T> ResolveProxy<T>(System.ClientModel.Primitives.IPersistableModel<T> model) { throw null; }
+        public bool TryGetProxy<T>([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] out System.ClientModel.Primitives.IJsonModel<T>? proxy) { throw null; }
+        public bool TryGetProxy<T>([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] out System.ClientModel.Primitives.IPersistableModel<T>? proxy) { throw null; }
     }
     public abstract partial class ModelReaderWriterTypeBuilder
     {

sdk/core/System.ClientModel/api/System.ClientModel.net8.0.cs

@@ -255,7 +255,13 @@ public partial class ModelReaderWriterOptions
         public ModelReaderWriterOptions(string format) { }
         public string Format { get { throw null; } }
         public static System.ClientModel.Primitives.ModelReaderWriterOptions Json { get { throw null; } }
+        public object? ProxiedModel { get { throw null; } }
         public static System.ClientModel.Primitives.ModelReaderWriterOptions Xml { get { throw null; } }
+        public void AddProxy<T>(System.ClientModel.Primitives.IPersistableModel<T> proxy) { }
+        public System.ClientModel.Primitives.IJsonModel<T> ResolveProxy<T>(System.ClientModel.Primitives.IJsonModel<T> model) { throw null; }
+        public System.ClientModel.Primitives.IPersistableModel<T> ResolveProxy<T>(System.ClientModel.Primitives.IPersistableModel<T> model) { throw null; }
+        public bool TryGetProxy<T>([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] out System.ClientModel.Primitives.IJsonModel<T>? proxy) { throw null; }
+        public bool TryGetProxy<T>([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] out System.ClientModel.Primitives.IPersistableModel<T>? proxy) { throw null; }
     }
     public abstract partial class ModelReaderWriterTypeBuilder
     {

sdk/core/System.ClientModel/api/System.ClientModel.netstandard2.0.cs

@@ -255,7 +255,13 @@ public partial class ModelReaderWriterOptions
         public ModelReaderWriterOptions(string format) { }
         public string Format { get { throw null; } }
         public static System.ClientModel.Primitives.ModelReaderWriterOptions Json { get { throw null; } }
+        public object? ProxiedModel { get { throw null; } }
         public static System.ClientModel.Primitives.ModelReaderWriterOptions Xml { get { throw null; } }
+        public void AddProxy<T>(System.ClientModel.Primitives.IPersistableModel<T> proxy) { }
+        public System.ClientModel.Primitives.IJsonModel<T> ResolveProxy<T>(System.ClientModel.Primitives.IJsonModel<T> model) { throw null; }
+        public System.ClientModel.Primitives.IPersistableModel<T> ResolveProxy<T>(System.ClientModel.Primitives.IPersistableModel<T> model) { throw null; }
+        public bool TryGetProxy<T>(out System.ClientModel.Primitives.IJsonModel<T>? proxy) { throw null; }
+        public bool TryGetProxy<T>(out System.ClientModel.Primitives.IPersistableModel<T>? proxy) { throw null; }
     }
     public abstract partial class ModelReaderWriterTypeBuilder
     {

sdk/core/System.ClientModel/samples/ModelReaderWriter.md

@@ -53,4 +53,48 @@ string json = @"{
       ""z"": 3
     }";
 OutputModel? model = JsonSerializer.Deserialize<OutputModel>(json, options);
-```
+```
+
+## Using a Proxy
+
+In more advanced scenarios a library user might want to override the behavior of how a model is read or written.
+In this case you can implement your own class which implements the same interface, either `IPersistableModel<T>` or `IJsonModel<T>`, and register it with the `ModelReaderWriterOptions`.
+Unlike the `PersistableModelProxy` attribute the proxy is only valid for a single instance of `ModelReaderWriterOptions` giving you more flexibility to turn it on or off.
+
+Using a proxy with the following definition
+
+```C# Snippet:Readme_Read_Proxy_ClassStub
+public class OutputModelProxy : IJsonModel<OutputModel>
+```
+
+The example below shows how to read JSON to create a strongly-typed model instance using a proxy.
+
+```C# Snippet:Readme_Read_Proxy
+string json = @"{
+      ""x"": 1,
+      ""y"": 2,
+      ""z"": 3
+    }";
+
+ModelReaderWriterOptions options = new ModelReaderWriterOptions("W");
+options.AddProxy(new OutputModelProxy());
+
+OutputModel? model = ModelReaderWriter.Read<OutputModel>(BinaryData.FromString(json), options);
+```
+
+Using a proxy with the following definition
+
+```C# Snippet:Readme_Write_Proxy_ClassStub
+public class InputModelProxy : IJsonModel<InputModel>
+```
+
+The example below shows how to write a persitable model using a proxy to `BinaryData`
+
+```C# Snippet:Readme_Write_Proxy
+InputModel model = new InputModel();
+
+ModelReaderWriterOptions options = new ModelReaderWriterOptions("W");
+options.AddProxy(new InputModelProxy());
+
+BinaryData data = ModelReaderWriter.Write(model, options);
+```

sdk/core/System.ClientModel/src/ModelReaderWriter/JsonCollectionReader.cs

@@ -57,7 +57,7 @@ private static void ReadJsonCollection(
         }
         else if (itemInstance is IJsonModel<object> iJsonModel)
         {
-            jsonModel = iJsonModel;
+            jsonModel = options.ResolveProxy(iJsonModel);
         }
         else
         {

sdk/core/System.ClientModel/src/ModelReaderWriter/JsonCollectionWriter.cs

@@ -26,7 +26,7 @@ private static void WriteJson(object model, Utf8JsonWriter writer, ModelReaderWr
         }
         else if (model is IJsonModel<object> jsonModel)
         {
-            jsonModel.Write(writer, options);
+            options.ResolveProxy(jsonModel).Write(writer, options);
         }
         else if (model is IEnumerable enumerable)
         {

sdk/core/System.ClientModel/src/ModelReaderWriter/JsonModelConverter.cs

@@ -20,8 +20,8 @@ namespace System.ClientModel.Primitives;
 public class JsonModelConverter : JsonConverter<IJsonModel<object>>
 #pragma warning restore AZC0014 // Avoid using banned types in public API
 {
-    private ModelReaderWriterOptions _options;
-    private ModelReaderWriterContext? _context;
+    private readonly ModelReaderWriterOptions _options;
+    private readonly ModelReaderWriterContext? _context;
 
     /// <summary>
     /// Initializes a new instance of <see cref="JsonModelConverter"/> with a default options of <see cref="ModelReaderWriterOptions.Json"/>.
@@ -87,7 +87,10 @@ public override IJsonModel<object> Read(ref Utf8JsonReader reader, Type typeToCo
             return context.GetTypeBuilder(typeToConvert).CreateObject() as IJsonModel<object>;
         }
 
-        IJsonModel<object>? iJsonModel = _context is null ? NonAotCompatActivate() : AotCompatActivate();
+        if (!_options.TryGetProxy(typeToConvert, out IJsonModel<object>? iJsonModel))
+        {
+            iJsonModel = _context is null ? NonAotCompatActivate() : AotCompatActivate();
+        }
 
         if (iJsonModel is null)
         {
@@ -101,6 +104,6 @@ public override IJsonModel<object> Read(ref Utf8JsonReader reader, Type typeToCo
     public override void Write(Utf8JsonWriter writer, IJsonModel<object> value, JsonSerializerOptions options)
 #pragma warning restore AZC0014 // Avoid using banned types in public API
     {
-        value.Write(writer, _options);
+        _options.ResolveProxy(value).Write(writer, _options);
     }
 }

sdk/core/System.ClientModel/src/ModelReaderWriter/ModelReaderWriter.cs

@@ -5,6 +5,7 @@
 using System.Collections;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
+using System.Text.Json;
 
 namespace System.ClientModel.Primitives;
 
@@ -32,9 +33,7 @@ public static BinaryData Write<T>(T model, ModelReaderWriterOptions? options = d
             throw new ArgumentNullException(nameof(model));
         }
 
-        options ??= ModelReaderWriterOptions.Json;
-
-        return WritePersistable(model, options);
+        return WritePersistable(model, GetOptions(options));
     }
 
     /// <summary>
@@ -53,13 +52,11 @@ public static BinaryData Write(object model, ModelReaderWriterOptions? options =
             throw new ArgumentNullException(nameof(model));
         }
 
-        options ??= ModelReaderWriterOptions.Json;
-
         //temp blocking this for symetry of functionality on read/write with no context.
         //will be allowed after https://github.com/Azure/azure-sdk-for-net/issues/48294
         if (model is IPersistableModel<object> iModel)
         {
-            return WritePersistable(iModel, options);
+            return WritePersistable(iModel, GetOptions(options));
         }
         else
         {
@@ -89,7 +86,7 @@ public static BinaryData Write<T>(T model, ModelReaderWriterOptions options, Mod
             throw new ArgumentNullException(nameof(model));
         }
 
-        return WritePersistableOrEnumerable(model, options, context);
+        return WritePersistableOrEnumerable(model, GetOptions(options), context);
     }
 
     /// <summary>
@@ -114,7 +111,7 @@ public static BinaryData Write(object model, ModelReaderWriterOptions options, M
             throw new ArgumentNullException(nameof(model));
         }
 
-        return WritePersistableOrEnumerable(model, options, context);
+        return WritePersistableOrEnumerable(model, GetOptions(options), context);
     }
 
     private static BinaryData WritePersistableOrEnumerable<T>(T model, ModelReaderWriterOptions options, ModelReaderWriterContext context)
@@ -154,7 +151,7 @@ private static BinaryData WritePersistable<T>(IPersistableModel<T> model, ModelR
         }
         else
         {
-            return model.Write(options);
+            return options.ResolveProxy(model).Write(options);
         }
     }
 
@@ -173,7 +170,7 @@ private static BinaryData WritePersistable<T>(IPersistableModel<T> model, ModelR
         ModelReaderWriterOptions? options = default)
         where T : IPersistableModel<T>
     {
-        return ReadInternal<T>(data, options ??= ModelReaderWriterOptions.Json, s_reflectionContext.Value);
+        return ReadInternal<T>(data, GetOptions(options), s_reflectionContext.Value);
     }
 
     /// <summary>
@@ -199,7 +196,7 @@ private static BinaryData WritePersistable<T>(IPersistableModel<T> model, ModelR
             throw new ArgumentNullException(nameof(context));
         }
 
-        return ReadInternal<T>(data, options, context);
+        return ReadInternal<T>(data, GetOptions(options), context);
     }
 
     /// <summary>
@@ -219,7 +216,7 @@ private static BinaryData WritePersistable<T>(IPersistableModel<T> model, ModelR
         [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)] Type returnType,
         ModelReaderWriterOptions? options = default)
     {
-        return ReadInternal(data, returnType, options ??= ModelReaderWriterOptions.Json, s_reflectionContext.Value);
+        return ReadInternal(data, returnType, GetOptions(options), s_reflectionContext.Value);
     }
 
     /// <summary>
@@ -247,7 +244,7 @@ private static BinaryData WritePersistable<T>(IPersistableModel<T> model, ModelR
             throw new ArgumentNullException(nameof(context));
         }
 
-        return ReadInternal(data, returnType, options, context);
+        return ReadInternal(data, returnType, GetOptions(options), context);
     }
 
     private static T? ReadInternal<T>(BinaryData data, ModelReaderWriterOptions options, ModelReaderWriterContext context)
@@ -277,7 +274,15 @@ private static BinaryData WritePersistable<T>(IPersistableModel<T> model, ModelR
         }
         else if (returnObj is IPersistableModel<object> persistableModel)
         {
-            return persistableModel.Create(data, options);
+            if (ShouldWriteAsJson(persistableModel, options, out IJsonModel<object>? jsonModel))
+            {
+                Utf8JsonReader reader = new(data);
+                return options.ResolveProxy(jsonModel).Create(ref reader, options);
+            }
+            else
+            {
+                return options.ResolveProxy(persistableModel).Create(data, options);
+            }
         }
         else
         {
@@ -305,4 +310,16 @@ internal static bool ShouldWriteAsJson<T>(IPersistableModel<T> model, ModelReade
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static bool IsJsonFormatRequested<T>(IPersistableModel<T> model, ModelReaderWriterOptions options)
         => options.Format == "J" || (options.Format == "W" && model.GetFormatFromOptions(options) == "J");
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static ModelReaderWriterOptions GetOptions(ModelReaderWriterOptions? options)
+    {
+        if (options is null)
+            return ModelReaderWriterOptions.Json;
+
+        if (options.IsCoreOwned)
+            return options;
+
+        return options.HasProxies ? new ModelReaderWriterOptions(options) : options;
+    }
 }