Add NO_COLOR, TERM=dumb, and --no-color support (#1556)

* Initial plan

* Add NO_COLOR, TERM=dumb, and --no-color support

Respect the NO_COLOR environment variable (https://no-color.org/),
TERM=dumb detection, and --no-color CLI flag to disable ANSI color
escape codes in output.

Changes:
- DevProxyCommand: Add NoColor static property and --no-color option
- DevProxyConfigOptions: Register --no-color for early parsing
- TextWriterExtensions: Skip ANSI codes when NoColor is true
- ProxyStateController: Skip Console color APIs when NoColor is true

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>

* Update DevProxy/Logging/TextWriterExtensions.cs

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

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
Co-authored-by: Waldek Mastykarz <waldek@mastykarz.nl>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Garry Trinder <garry@trinder365.co.uk>

Author: 4 people

DevProxy/Commands/DevProxyCommand.cs

@@ -43,6 +43,7 @@ sealed class DevProxyCommand : RootCommand
     internal const string OutputOptionName = "--output";
     internal const string DetachedOptionName = "--detach";
     internal const string InternalDaemonOptionName = "--_internal-daemon";
+    internal const string NoColorOptionName = "--no-color";
 
     private static readonly string[] globalOptions = ["--version"];
     private static readonly string[] helpOptions = ["--help", "-h", "/h", "-?", "/?"];
@@ -56,6 +57,7 @@ sealed class DevProxyCommand : RootCommand
     private static bool _isInternalDaemonResolved;
     private static bool _stdioLogFilePathResolved;
     private static bool _detachedLogFilePathResolved;
+    private static bool _noColorResolved;
 
     public static bool HasGlobalOptions
     {
@@ -214,6 +216,24 @@ public static string DetachedLogFilePath
         }
     }
 
+    public static bool NoColor
+    {
+        get
+        {
+            if (_noColorResolved)
+            {
+                return field;
+            }
+
+            var args = Environment.GetCommandLineArgs();
+            field = args.Contains(NoColorOptionName) ||
+                Environment.GetEnvironmentVariable("NO_COLOR") is not null ||
+                string.Equals(Environment.GetEnvironmentVariable("TERM"), "dumb", StringComparison.OrdinalIgnoreCase);
+            _noColorResolved = true;
+            return field;
+        }
+    }
+
     public DevProxyCommand(
         IEnumerable<IPlugin> plugins,
         ISet<UrlToWatch> urlsToWatch,
@@ -522,6 +542,13 @@ private void ConfigureCommand()
             Hidden = true
         };
 
+        var noColorOption = new Option<bool>(NoColorOptionName)
+        {
+            Description = "Disable colored output",
+            Arity = ArgumentArity.Zero,
+            Recursive = true
+        };
+
         var options = new List<Option>
         {
             apiPortOption,
@@ -534,6 +561,7 @@ private void ConfigureCommand()
             internalDaemonOption,
             ipAddressOption,
             logLevelOption,
+            noColorOption,
             noFirstRunOption,
             noWatchOption,
             outputOption,

DevProxy/Commands/DevProxyConfigOptions.cs

@@ -145,6 +145,11 @@ public DevProxyConfigOptions()
             Arity = ArgumentArity.Zero
         };
 
+        var noColorOption = new Option<bool>(DevProxyCommand.NoColorOptionName)
+        {
+            Arity = ArgumentArity.Zero
+        };
+
         var options = new List<Option>
         {
             apiPortOption,
@@ -154,7 +159,8 @@ public DevProxyConfigOptions()
             urlsToWatchOption,
             logLevelOption,
             outputOption,
-            discoverOption
+            discoverOption,
+            noColorOption
         };
         this.AddOptions(options.OrderByName());
 

DevProxy/Logging/TextWriterExtensions.cs

@@ -2,6 +2,7 @@
 // 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.Commands;
 using DevProxy.Logging;
 
 #pragma warning disable IDE0130
@@ -15,13 +16,18 @@ static class TextWriterExtensions
 
     public static void ResetColor(this TextWriter writer)
     {
+        if (Console.IsOutputRedirected || DevProxyCommand.NoColor)
+        {
+            return;
+        }
+
         writer.Write(_defaultForegroundColor);
         writer.Write(_defaultBackgroundColor);
     }
 
     public static void WriteColoredMessage(this TextWriter textWriter, string message, ConsoleColor? background, ConsoleColor? foreground)
     {
-        if (Console.IsOutputRedirected)
+        if (Console.IsOutputRedirected || DevProxyCommand.NoColor)
         {
             textWriter.Write(message);
             return;

DevProxy/Proxy/ProxyStateController.cs

@@ -4,6 +4,7 @@
 
 using DevProxy.Abstractions.Plugins;
 using DevProxy.Abstractions.Proxy;
+using DevProxy.Commands;
 using Titanium.Web.Proxy;
 
 namespace DevProxy.Proxy;
@@ -95,9 +96,15 @@ private static void PrintRecordingIndicator(bool isRecording)
         {
             if (isRecording)
             {
-                Console.ForegroundColor = ConsoleColor.Red;
+                if (!DevProxyCommand.NoColor)
+                {
+                    Console.ForegroundColor = ConsoleColor.Red;
+                }
                 Console.Error.Write("◉");
-                Console.ResetColor();
+                if (!DevProxyCommand.NoColor)
+                {
+                    Console.ResetColor();
+                }
                 Console.Error.WriteLine(" Recording... ");
             }
             else