Make McpJsonUtilities public and remove IVT to sample (#5)

Also adds in the same encoder used by AIJsonUtilities.

src/ModelContextProtocol/Utils/Json/McpJsonUtilities.cs

@@ -0,0 +1,102 @@
+using ModelContextProtocol.Protocol.Messages;
+using ModelContextProtocol.Protocol.Types;
+using System.Diagnostics.CodeAnalysis;
+using System.Text.Encodings.Web;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using System.Text.Json.Serialization;
+using System.Text.Json.Serialization.Metadata;
+
+namespace ModelContextProtocol.Utils.Json;
+
+/// <summary>Provides a collection of utility methods for working with JSON data in the context of MCP.</summary>
+public static partial class McpJsonUtilities
+{
+    /// <summary>
+    /// Gets the <see cref="JsonSerializerOptions"/> singleton used as the default in JSON serialization operations.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// For Native AOT or applications disabling <see cref="JsonSerializer.IsReflectionEnabledByDefault"/>, this instance 
+    /// includes source generated contracts for all common exchange types contained in the ModelContextProtocol library.
+    /// </para>
+    /// <para>
+    /// It additionally turns on the following settings:
+    /// <list type="number">
+    /// <item>Enables string-based enum serialization as implemented by <see cref="JsonStringEnumConverter"/>.</item>
+    /// <item>Enables <see cref="JsonIgnoreCondition.WhenWritingNull"/> as the default ignore condition for properties.</item>
+    /// <item>Enables <see cref="JsonNumberHandling.AllowReadingFromString"/> as the default number handling for number types.</item>
+    /// <item>
+    /// Enables <see cref="JavaScriptEncoder.UnsafeRelaxedJsonEscaping"/> when escaping JSON strings.
+    /// Consuming applications must ensure that JSON outputs are adequately escaped before embedding in other document formats,
+    /// such as HTML and XML.
+    /// </item>
+    /// </list>
+    /// </para>
+    /// </remarks>
+    public static JsonSerializerOptions DefaultOptions { get; } = CreateDefaultOptions();
+
+    /// <summary>
+    /// Creates default options to use for MCP-related serialization.
+    /// </summary>
+    /// <returns>The configured options.</returns>
+    [UnconditionalSuppressMessage("AotAnalysis", "IL3050", Justification = "DefaultJsonTypeInfoResolver is only used when reflection-based serialization is enabled")]
+    [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026", Justification = "DefaultJsonTypeInfoResolver is only used when reflection-based serialization is enabled")]
+    private static JsonSerializerOptions CreateDefaultOptions()
+    {
+        // If reflection-based serialization is enabled by default, use it, as it's the most permissive in terms of what it can serialize,
+        // and we want to be flexible in terms of what can be put into the various collections in the object model.
+        // Otherwise, use the source-generated options to enable trimming and Native AOT.
+        JsonSerializerOptions options;
+
+        if (JsonSerializer.IsReflectionEnabledByDefault)
+        {
+            // Keep in sync with the JsonSourceGenerationOptions attribute on JsonContext below.
+            options = new(JsonSerializerDefaults.Web)
+            {
+                TypeInfoResolver = new DefaultJsonTypeInfoResolver(),
+                Converters = { new JsonStringEnumConverter() },
+                DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+                NumberHandling = JsonNumberHandling.AllowReadingFromString,
+                Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
+            };
+        }
+        else
+        {
+            options = new(JsonContext.Default.Options)
+            {
+                // Compile-time encoder setting not yet available
+                Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
+            };
+        }
+
+        options.MakeReadOnly();
+        return options;
+    }
+
+    internal static JsonTypeInfo<T> GetTypeInfo<T>(this JsonSerializerOptions options) =>
+        (JsonTypeInfo<T>)options.GetTypeInfo(typeof(T));
+
+    // Keep in sync with CreateDefaultOptions above.
+    [JsonSourceGenerationOptions(JsonSerializerDefaults.Web,
+        UseStringEnumConverter = true,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+        NumberHandling = JsonNumberHandling.AllowReadingFromString)]
+    [JsonSerializable(typeof(JsonDocument))]
+    [JsonSerializable(typeof(JsonElement))]
+    [JsonSerializable(typeof(JsonNode))]
+    [JsonSerializable(typeof(IJsonRpcMessage))]
+    [JsonSerializable(typeof(JsonRpcRequest))]
+    [JsonSerializable(typeof(JsonRpcNotification))]
+    [JsonSerializable(typeof(JsonRpcResponse))]
+    [JsonSerializable(typeof(JsonRpcError))]
+    [JsonSerializable(typeof(ServerCapabilities))]
+    [JsonSerializable(typeof(ClientCapabilities))]
+    [JsonSerializable(typeof(Implementation))]
+    [JsonSerializable(typeof(CreateMessageResult))]
+    [JsonSerializable(typeof(ListRootsResult))]
+    [JsonSerializable(typeof(InitializeResult))]
+    [JsonSerializable(typeof(JsonSchema))]
+    [JsonSerializable(typeof(CallToolResponse))]
+    internal sealed partial class JsonContext : JsonSerializerContext;
+}