Proxy stdio traffic (#1485)

* Basics

* Logging

* MCP fix

* Plugins

* LogRequest

* DevToolPlugin support

* Logging to Dev Tools Plugin

* Proper name

* Fix display name

* Misc fixes

* Mock stdio

* Fixes

* Update MockStdioResponsePlugin schema to version 2.1.0 and add configuration schema

* Adds support for specifying config for stdio

* Update DevProxy.Abstractions/Models/MockStdioResponse.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Review fixes

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: waldekmastykarz

DevProxy.Abstractions/Extensions/ILoggerExtensions.cs

@@ -17,10 +17,34 @@ public static void LogRequest(this ILogger logger, string message, MessageType m
         logger.Log(new RequestLog(message, messageType, method, url));
     }
 
+    public static void LogRequest(this ILogger logger, string message, MessageType messageType, StdioLoggingContext context)
+    {
+        logger.Log(new StdioLogEntry(message, messageType, context));
+    }
+
     public static void Log(this ILogger logger, RequestLog message)
     {
         ArgumentNullException.ThrowIfNull(logger);
 
         logger.Log(LogLevel.Information, 0, message, exception: null, (m, _) => JsonSerializer.Serialize(m));
     }
+
+    public static void Log(this ILogger logger, StdioLogEntry message)
+    {
+        ArgumentNullException.ThrowIfNull(logger);
+
+        logger.Log(LogLevel.Information, 0, message, exception: null, (m, _) => JsonSerializer.Serialize(m));
+    }
+}
+
+/// <summary>
+/// Represents a log entry for stdio operations.
+/// </summary>
+public class StdioLogEntry(string message, MessageType messageType, StdioLoggingContext? context)
+{
+    public string Message { get; set; } = message ?? throw new ArgumentNullException(nameof(message));
+    public MessageType MessageType { get; set; } = messageType;
+    public string? Command { get; init; } = context?.Session.Command;
+    public string? Direction { get; init; } = context?.Direction.ToString();
+    public string? PluginName { get; set; }
 }

DevProxy.Abstractions/Models/MockStdioResponse.cs

@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json;
+
+namespace DevProxy.Abstractions.Models;
+
+/// <summary>
+/// Represents a mock response for stdio operations.
+/// </summary>
+public class MockStdioResponse : ICloneable
+{
+    /// <summary>
+    /// The request pattern to match against stdin.
+    /// </summary>
+    public MockStdioRequest? Request { get; set; }
+
+    /// <summary>
+    /// The mock response to return.
+    /// </summary>
+    public MockStdioResponseBody? Response { get; set; }
+
+    public object Clone()
+    {
+        var json = JsonSerializer.Serialize(this);
+        return JsonSerializer.Deserialize<MockStdioResponse>(json) ?? new MockStdioResponse();
+    }
+}
+
+/// <summary>
+/// Represents the request pattern for matching stdin.
+/// </summary>
+public class MockStdioRequest
+{
+    /// <summary>
+    /// A fragment of the stdin body to match.
+    /// If null or empty, the mock matches any stdin (or is applied immediately on startup).
+    /// </summary>
+    public string? BodyFragment { get; set; }
+
+    /// <summary>
+    /// The Nth occurrence to match. If null, matches every occurrence.
+    /// </summary>
+    public int? Nth { get; set; }
+}
+
+/// <summary>
+/// Represents the mock response body for stdio.
+/// </summary>
+public class MockStdioResponseBody
+{
+    /// <summary>
+    /// The stdout content to return. Can be a string or a JSON object.
+    /// If the value starts with @, it's treated as a file path.
+    /// </summary>
+    public object? Stdout { get; set; }
+
+    /// <summary>
+    /// The stderr content to return. Can be a string or a JSON object.
+    /// If the value starts with @, it's treated as a file path.
+    /// </summary>
+    public object? Stderr { get; set; }
+}

DevProxy.Abstractions/Plugins/BasePlugin.cs

@@ -16,7 +16,7 @@ namespace DevProxy.Abstractions.Plugins;
 
 public abstract class BasePlugin(
     ILogger logger,
-    ISet<UrlToWatch> urlsToWatch) : IPlugin, IDisposable
+    ISet<UrlToWatch> urlsToWatch) : IPlugin, IDisposable, IStdioPlugin
 {
     public bool Enabled { get; protected set; } = true;
     protected ILogger Logger { get; } = logger;
@@ -36,6 +36,7 @@ public virtual void OptionsLoaded(OptionsLoadedArgs e)
     {
     }
 
+    // HTTP plugin methods
     public virtual Task BeforeRequestAsync(ProxyRequestArgs e, CancellationToken cancellationToken)
     {
         return Task.CompletedTask;
@@ -66,6 +67,32 @@ public virtual Task MockRequestAsync(EventArgs e, CancellationToken cancellation
         return Task.CompletedTask;
     }
 
+    // Stdio plugin methods
+    public virtual Task BeforeStdinAsync(StdioRequestArgs e, CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+
+    public virtual Task AfterStdoutAsync(StdioResponseArgs e, CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+
+    public virtual Task AfterStderrAsync(StdioResponseArgs e, CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+
+    public virtual Task AfterStdioRequestLogAsync(StdioRequestLogArgs e, CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+
+    public virtual Task AfterStdioRecordingStopAsync(StdioRecordingArgs e, CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+    
     protected virtual void Dispose(bool disposing)
     {
         // Override in derived classes to dispose managed resources

DevProxy.Abstractions/Plugins/IStdioPlugin.cs

@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using DevProxy.Abstractions.Proxy;
+
+namespace DevProxy.Abstractions.Plugins;
+
+/// <summary>
+/// Interface for plugins that can intercept stdio messages.
+/// Plugins that implement both IPlugin and IStdioPlugin can participate
+/// in both HTTP proxy and stdio proxy scenarios.
+/// </summary>
+public interface IStdioPlugin
+{
+    /// <summary>
+    /// Gets the name of the plugin.
+    /// </summary>
+    string Name { get; }
+
+    /// <summary>
+    /// Gets whether the plugin is enabled.
+    /// </summary>
+    bool Enabled { get; }
+
+    /// <summary>
+    /// Called before stdin message is forwarded to the child process.
+    /// Plugins can inspect, modify, or consume the message.
+    /// Set ResponseState.HasBeenSet to true to prevent the message from being forwarded.
+    /// </summary>
+    /// <param name="e">The event arguments containing the stdin message.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    Task BeforeStdinAsync(StdioRequestArgs e, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// Called after stdout message is received from the child process.
+    /// Plugins can inspect, modify, or consume the message.
+    /// Set ResponseState.HasBeenSet to true to prevent the message from being forwarded.
+    /// </summary>
+    /// <param name="e">The event arguments containing the stdout message.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    Task AfterStdoutAsync(StdioResponseArgs e, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// Called after stderr message is received from the child process.
+    /// Plugins can inspect, modify, or consume the message.
+    /// Set ResponseState.HasBeenSet to true to prevent the message from being forwarded.
+    /// </summary>
+    /// <param name="e">The event arguments containing the stderr message.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    Task AfterStderrAsync(StdioResponseArgs e, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// Called after a stdin/stdout pair has been logged.
+    /// Useful for recording and reporting plugins.
+    /// </summary>
+    /// <param name="e">The event arguments containing the request log.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    Task AfterStdioRequestLogAsync(StdioRequestLogArgs e, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// Called after recording has stopped.
+    /// Useful for reporting plugins that need to process all recorded messages.
+    /// </summary>
+    /// <param name="e">The event arguments containing all recorded logs.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    Task AfterStdioRecordingStopAsync(StdioRecordingArgs e, CancellationToken cancellationToken);
+}

DevProxy.Abstractions/Proxy/IProxyLogger.cs

@@ -26,4 +26,10 @@ public enum MessageType
 public class LoggingContext(SessionEventArgs session)
 {
     public SessionEventArgs Session { get; } = session;
+}
+
+public class StdioLoggingContext(StdioSession session, StdioMessageDirection direction)
+{
+    public StdioSession Session { get; } = session;
+    public StdioMessageDirection Direction { get; } = direction;
 }