Wrap each request in a service scope (#276)

* Wrap each request in a service scope

* Change request/notification delegates to return ValueTask

* Address feedback

src/ModelContextProtocol/Protocol/Transport/StreamServerTransport.cs

@@ -82,7 +82,7 @@ public class StreamServerTransport : TransportBase
 
             await JsonSerializer.SerializeAsync(_outputStream, message, McpJsonUtilities.DefaultOptions.GetTypeInfo(typeof(IJsonRpcMessage)), cancellationToken).ConfigureAwait(false);
             await _outputStream.WriteAsync(s_newlineBytes, cancellationToken).ConfigureAwait(false);
-            await _outputStream.FlushAsync(cancellationToken).ConfigureAwait(false);;
+            await _outputStream.FlushAsync(cancellationToken).ConfigureAwait(false);
 
             _logger.TransportSentMessage(_endpointName, id);
         }

src/ModelContextProtocol/Protocol/Types/ClientCapabilities.cs

@@ -77,5 +77,5 @@ public class ClientCapabilities
     /// </para>
     /// </remarks>
     [JsonIgnore]
-    public IEnumerable<KeyValuePair<string, Func<JsonRpcNotification, CancellationToken, Task>>>? NotificationHandlers { get; set; }
+    public IEnumerable<KeyValuePair<string, Func<JsonRpcNotification, CancellationToken, ValueTask>>>? NotificationHandlers { get; set; }
 }

src/ModelContextProtocol/Protocol/Types/CompletionsCapability.cs

@@ -33,5 +33,5 @@ public class CompletionsCapability
     /// and should return appropriate completion suggestions.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<CompleteRequestParams>, CancellationToken, Task<CompleteResult>>? CompleteHandler { get; set; }
+    public Func<RequestContext<CompleteRequestParams>, CancellationToken, ValueTask<CompleteResult>>? CompleteHandler { get; set; }
 }

src/ModelContextProtocol/Protocol/Types/EmptyResult.cs

@@ -9,5 +9,5 @@ namespace ModelContextProtocol.Protocol.Types;
 public class EmptyResult
 {
     [JsonIgnore]
-    internal static Task<EmptyResult> CompletedTask { get; } = Task.FromResult(new EmptyResult());
+    internal static EmptyResult Instance { get; } = new();
 }

src/ModelContextProtocol/Protocol/Types/LoggingCapability.cs

@@ -19,5 +19,5 @@ public class LoggingCapability
     /// Gets or sets the handler for set logging level requests from clients.
     /// </summary>
     [JsonIgnore]
-    public Func<RequestContext<SetLevelRequestParams>, CancellationToken, Task<EmptyResult>>? SetLoggingLevelHandler { get; set; }
+    public Func<RequestContext<SetLevelRequestParams>, CancellationToken, ValueTask<EmptyResult>>? SetLoggingLevelHandler { get; set; }
 }

src/ModelContextProtocol/Protocol/Types/PromptsCapability.cs

@@ -41,7 +41,7 @@ public class PromptsCapability
     /// along with any prompts defined in <see cref="PromptCollection"/>.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<ListPromptsRequestParams>, CancellationToken, Task<ListPromptsResult>>? ListPromptsHandler { get; set; }
+    public Func<RequestContext<ListPromptsRequestParams>, CancellationToken, ValueTask<ListPromptsResult>>? ListPromptsHandler { get; set; }
 
     /// <summary>
     /// Gets or sets the handler for <see cref="RequestMethods.PromptsGet"/> requests.
@@ -58,7 +58,7 @@ public class PromptsCapability
     /// </para>
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<GetPromptRequestParams>, CancellationToken, Task<GetPromptResult>>? GetPromptHandler { get; set; }
+    public Func<RequestContext<GetPromptRequestParams>, CancellationToken, ValueTask<GetPromptResult>>? GetPromptHandler { get; set; }
 
     /// <summary>
     /// Gets or sets a collection of prompts that will be served by the server.

src/ModelContextProtocol/Protocol/Types/ResourcesCapability.cs

@@ -40,7 +40,7 @@ public class ResourcesCapability
     /// allowing clients to discover available resource types and their access patterns.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<ListResourceTemplatesRequestParams>, CancellationToken, Task<ListResourceTemplatesResult>>? ListResourceTemplatesHandler { get; set; }
+    public Func<RequestContext<ListResourceTemplatesRequestParams>, CancellationToken, ValueTask<ListResourceTemplatesResult>>? ListResourceTemplatesHandler { get; set; }
 
     /// <summary>
     /// Gets or sets the handler for <see cref="RequestMethods.ResourcesList"/> requests.
@@ -50,7 +50,7 @@ public class ResourcesCapability
     /// The implementation should return a <see cref="ListResourcesResult"/> with the matching resources.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<ListResourcesRequestParams>, CancellationToken, Task<ListResourcesResult>>? ListResourcesHandler { get; set; }
+    public Func<RequestContext<ListResourcesRequestParams>, CancellationToken, ValueTask<ListResourcesResult>>? ListResourcesHandler { get; set; }
 
     /// <summary>
     /// Gets or sets the handler for <see cref="RequestMethods.ResourcesRead"/> requests.
@@ -62,7 +62,7 @@ public class ResourcesCapability
     /// its contents in a ReadResourceResult object.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<ReadResourceRequestParams>, CancellationToken, Task<ReadResourceResult>>? ReadResourceHandler { get; set; }
+    public Func<RequestContext<ReadResourceRequestParams>, CancellationToken, ValueTask<ReadResourceResult>>? ReadResourceHandler { get; set; }
 
     /// <summary>
     /// Gets or sets the handler for <see cref="RequestMethods.ResourcesSubscribe"/> requests.
@@ -75,7 +75,7 @@ public class ResourcesCapability
     /// requiring polling.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<SubscribeRequestParams>, CancellationToken, Task<EmptyResult>>? SubscribeToResourcesHandler { get; set; }
+    public Func<RequestContext<SubscribeRequestParams>, CancellationToken, ValueTask<EmptyResult>>? SubscribeToResourcesHandler { get; set; }
 
     /// <summary>
     /// Gets or sets the handler for <see cref="RequestMethods.ResourcesUnsubscribe"/> requests.
@@ -86,5 +86,5 @@ public class ResourcesCapability
     /// about the specified resource.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<UnsubscribeRequestParams>, CancellationToken, Task<EmptyResult>>? UnsubscribeFromResourcesHandler { get; set; }
+    public Func<RequestContext<UnsubscribeRequestParams>, CancellationToken, ValueTask<EmptyResult>>? UnsubscribeFromResourcesHandler { get; set; }
 }

src/ModelContextProtocol/Protocol/Types/RootsCapability.cs

@@ -41,5 +41,5 @@ public class RootsCapability
     /// The handler receives request parameters and should return a <see cref="ListRootsResult"/> containing the collection of available roots.
     /// </remarks>
     [JsonIgnore]
-    public Func<ListRootsRequestParams?, CancellationToken, Task<ListRootsResult>>? RootsHandler { get; set; }
+    public Func<ListRootsRequestParams?, CancellationToken, ValueTask<ListRootsResult>>? RootsHandler { get; set; }
 }

src/ModelContextProtocol/Protocol/Types/SamplingCapability.cs

@@ -40,5 +40,5 @@ public class SamplingCapability
     /// </para>
     /// </remarks>
     [JsonIgnore]
-    public Func<CreateMessageRequestParams?, IProgress<ProgressNotificationValue>, CancellationToken, Task<CreateMessageResult>>? SamplingHandler { get; set; }
+    public Func<CreateMessageRequestParams?, IProgress<ProgressNotificationValue>, CancellationToken, ValueTask<CreateMessageResult>>? SamplingHandler { get; set; }
 }

src/ModelContextProtocol/Protocol/Types/ServerCapabilities.cs

@@ -83,5 +83,5 @@ public class ServerCapabilities
     /// </para>
     /// </remarks>
     [JsonIgnore]
-    public IEnumerable<KeyValuePair<string, Func<JsonRpcNotification, CancellationToken, Task>>>? NotificationHandlers { get; set; }
+    public IEnumerable<KeyValuePair<string, Func<JsonRpcNotification, CancellationToken, ValueTask>>>? NotificationHandlers { get; set; }
 }

src/ModelContextProtocol/Protocol/Types/ToolsCapability.cs

@@ -34,7 +34,7 @@ public class ToolsCapability
     /// and the tools from the collection will be combined to form the complete list of available tools.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<ListToolsRequestParams>, CancellationToken, Task<ListToolsResult>>? ListToolsHandler { get; set; }
+    public Func<RequestContext<ListToolsRequestParams>, CancellationToken, ValueTask<ListToolsResult>>? ListToolsHandler { get; set; }
 
     /// <summary>
     /// Gets or sets the handler for <see cref="RequestMethods.ToolsCall"/> requests.
@@ -46,7 +46,7 @@ public class ToolsCapability
     /// being called and its arguments, and should return a <see cref="CallToolResponse"/> with the execution results.
     /// </remarks>
     [JsonIgnore]
-    public Func<RequestContext<CallToolRequestParams>, CancellationToken, Task<CallToolResponse>>? CallToolHandler { get; set; }
+    public Func<RequestContext<CallToolRequestParams>, CancellationToken, ValueTask<CallToolResponse>>? CallToolHandler { get; set; }
 
     /// <summary>
     /// Gets or sets a collection of tools served by the server.