Wrap each request in a service scope (#276)

* Wrap each request in a service scope

* Change request/notification delegates to return ValueTask

* Address feedback

tests/ModelContextProtocol.Tests/Configuration/McpServerScopedTests.cs

@@ -0,0 +1,75 @@
+using Microsoft.Extensions.DependencyInjection;
+using ModelContextProtocol.Client;
+using ModelContextProtocol.Server;
+using ModelContextProtocol.Utils.Json;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Tests.Configuration;
+
+public partial class McpServerScopedTests : ClientServerTestBase
+{
+    public McpServerScopedTests(ITestOutputHelper testOutputHelper)
+        : base(testOutputHelper)
+    {
+    }
+
+    protected override void ConfigureServices(ServiceCollection services, IMcpServerBuilder mcpServerBuilder)
+    {
+        mcpServerBuilder.WithTools<EchoTool>(serializerOptions: McpServerScopedTestsJsonContext.Default.Options);
+        services.AddScoped(_ => new ComplexObject() { Name = "Scoped" });
+    }
+
+    [Fact]
+    public async Task InjectScopedServiceAsArgument()
+    {
+        IMcpClient client = await CreateMcpClientForServer();
+
+        var tools = await client.ListToolsAsync(McpServerScopedTestsJsonContext.Default.Options, TestContext.Current.CancellationToken);
+        var tool = tools.First(t => t.Name == nameof(EchoTool.EchoComplex));
+        Assert.DoesNotContain("\"complex\"", JsonSerializer.Serialize(tool.JsonSchema, McpJsonUtilities.DefaultOptions));
+
+        int startingConstructed = ComplexObject.Constructed;
+        int startingDisposed = ComplexObject.Disposed;
+
+        for (int i = 1; i <= 10; i++)
+        {
+            Assert.Contains("\"Scoped\"", JsonSerializer.Serialize(await tool.InvokeAsync(cancellationToken: TestContext.Current.CancellationToken), McpJsonUtilities.DefaultOptions));
+
+            Assert.Equal(startingConstructed + i, ComplexObject.Constructed);
+            Assert.Equal(startingDisposed + i, ComplexObject.Disposed);
+        }
+    }
+
+    [McpServerToolType]
+    public sealed class EchoTool()
+    {
+        [McpServerTool]
+        public static string EchoComplex(ComplexObject complex) => complex.Name!;
+    }
+
+    public class ComplexObject : IAsyncDisposable
+    {
+        public static int Constructed;
+        public static int Disposed;
+
+        public ComplexObject()
+        {
+            Interlocked.Increment(ref Constructed);
+        }
+
+        public ValueTask DisposeAsync()
+        {
+            Interlocked.Increment(ref Disposed);
+            return default;
+        }
+
+        public string? Name { get; set; }
+        public int Age { get; set; }
+    }
+
+    [JsonSerializable(typeof(string))]
+    [JsonSerializable(typeof(ComplexObject))]
+    [JsonSerializable(typeof(JsonElement))]
+    partial class McpServerScopedTestsJsonContext : JsonSerializerContext;
+}