From 314e0dd003eaa7831f4c060933dd23f3eabf8acd Mon Sep 17 00:00:00 2001
From: filzrev <103790468+filzrev@users.noreply.github.com>
Date: Fri, 26 Dec 2025 14:18:25 +0900
Subject: [PATCH 1/2] chore: fix exception logging on stdout redirected
 environment

---
 .../Extensions/SpectreConsoleExtensions.cs    | 35 +++++++++++++++++
 src/docfx/Program.cs                          | 39 ++++++++++++-------
 2 files changed, 59 insertions(+), 15 deletions(-)
 create mode 100644 src/docfx/Extensions/SpectreConsoleExtensions.cs

diff --git a/src/docfx/Extensions/SpectreConsoleExtensions.cs b/src/docfx/Extensions/SpectreConsoleExtensions.cs
new file mode 100644
index 00000000000..b7bcaa1abcc
--- /dev/null
+++ b/src/docfx/Extensions/SpectreConsoleExtensions.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Spectre.Console;
+using Spectre.Console.Cli;
+
+namespace Docfx;
+
+internal static class SpectreConsoleExtensions
+{
+    public static void WriteException(this IAnsiConsole ansiConsole, Exception e)
+    {
+        if (e is CommandAppException cae)
+        {
+            if (cae.Pretty is { } pretty)
+                AnsiConsole.Write(pretty);
+            else
+                AnsiConsole.MarkupInterpolated($"[red]Error:[/] {e.Message}");
+            return;
+        }
+        else
+        {
+            AnsiConsole.WriteException(e, new ExceptionSettings()
+            {
+                Format = ExceptionFormats.ShortenEverything,
+                Style = new()
+                {
+                    ParameterName = Color.Grey,
+                    ParameterType = Color.Grey78,
+                    LineNumber = Color.Grey78,
+                },
+            });
+        }
+    }
+}
diff --git a/src/docfx/Program.cs b/src/docfx/Program.cs
index 03df088dd6e..b71bb354f17 100644
--- a/src/docfx/Program.cs
+++ b/src/docfx/Program.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using Docfx.Common;
 using Spectre.Console;
 using Spectre.Console.Cli;
 
@@ -39,26 +40,34 @@ internal static int Main(string[] args)
 
         static void OnException(Exception e, ITypeResolver? resolver)
         {
-            if (e is CommandAppException cae)
+            // Try to unwrap AggregateException.
+            if (e is AggregateException ae && ae.InnerExceptions.Count == 1)
+                e = ae.InnerExceptions[0];
+
+            if (!Console.IsOutputRedirected)
             {
-                if (cae.Pretty is { } pretty)
-                    AnsiConsole.Write(pretty);
-                else
-                    AnsiConsole.MarkupInterpolated($"[red]Error:[/] {e.Message}");
+                // Write exception to console.
+                AnsiConsole.Console.WriteException(e);
+
+                // Write exception to ReportLogListener if exists.
+                var reportLogListener = Logger.FindListener(x => x is ReportLogListener);
+                reportLogListener?.WriteLine(Logger.GetLogItem(LogLevel.Error, e.ToString(), code: ErrorCodes.Build.FatalError));
             }
             else
             {
-                AnsiConsole.WriteException(e, new ExceptionSettings()
-                {
-                    Format = ExceptionFormats.ShortenEverything,
-                    Style = new()
-                    {
-                        ParameterName = Color.Grey,
-                        ParameterType = Color.Grey78,
-                        LineNumber = Color.Grey78,
-                    },
-                });
+                // Write exception with Logger API if stdout is redirected.
+                // To avoid line wrap issue https://github.com/spectreconsole/spectre.console/issues/1782
+                var exceptions = e is AggregateException ae2
+                    ? ae2.Flatten().InnerExceptions.ToArray()
+                    : [e];
+
+                foreach (var ex in exceptions)
+                    Logger.LogError(e.ToString(), code: ErrorCodes.Build.FatalError);
             }
+
+            // Cleanup logger.
+            Logger.Flush();
+            Logger.UnregisterAllListeners();
         }
     }
 }

From 8be6b0858d342084315dbf235fcb21e7976fbb49 Mon Sep 17 00:00:00 2001
From: filzrev <103790468+filzrev@users.noreply.github.com>
Date: Fri, 26 Dec 2025 20:10:07 +0900
Subject: [PATCH 2/2] chore: fix failed test on CI by resetting error count

---
 test/docfx.Tests/CommandLineTest.cs | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/test/docfx.Tests/CommandLineTest.cs b/test/docfx.Tests/CommandLineTest.cs
index ad509286aff..66abb6b1288 100644
--- a/test/docfx.Tests/CommandLineTest.cs
+++ b/test/docfx.Tests/CommandLineTest.cs
@@ -1,10 +1,12 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using Docfx.Common;
+
 namespace Docfx.Tests;
 
 [Collection("docfx STA")]
-public static class CommandLineTest
+public class CommandLineTest
 {
     [Fact]
     public static void PrintsVersion()
@@ -31,7 +33,14 @@ public static void PrintsHelp()
     [Fact]
     public static void FailForUnknownArgs()
     {
-        Assert.Equal(-1, Program.Main(["--unknown"]));
+        try
+        {
+            Assert.Equal(-1, Program.Main(["--unknown"]));
+        }
+        finally
+        {
+            Logger.ResetCount();
+        }
     }
 
     [Fact]