Highjacking console when completing

src/Spectre.Console.Cli/Completion/HighjackedAnsiConsole.cs

@@ -0,0 +1,26 @@
+namespace Spectre.Console.Cli.Completion;
+
+internal class HighjackedAnsiConsole : IAnsiConsole
+{
+    public IAnsiConsole OriginalConsole { get; }
+
+    public HighjackedAnsiConsole(IAnsiConsole console)
+    {
+        OriginalConsole = console;
+    }
+
+    public Profile Profile => OriginalConsole.Profile;
+
+    public IAnsiConsoleCursor Cursor => OriginalConsole.Cursor;
+    public IAnsiConsoleInput Input => OriginalConsole.Input;
+    public IExclusivityMode ExclusivityMode => OriginalConsole.ExclusivityMode;
+    public RenderPipeline Pipeline => OriginalConsole.Pipeline;
+
+    public void Clear(bool home)
+    {
+    }
+
+    public void Write(IRenderable renderable)
+    {
+    }
+}

src/Spectre.Console.Cli/Completion/HighjackedTextWriter.cs

@@ -0,0 +1,25 @@
+namespace Spectre.Console.Cli.Completion;
+
+internal class HighjackedTextWriter : TextWriter
+{
+    public override Encoding Encoding => Encoding.UTF8;
+
+    public TextWriter OriginalWriter { get; }
+
+    public HighjackedTextWriter(TextWriter originalWriter)
+    {
+        OriginalWriter = originalWriter;
+    }
+
+    public override void Write(char value)
+    {
+    }
+
+    public override void Write(string? value)
+    {
+    }
+
+    public override void WriteLine(string? value)
+    {
+    }
+}

src/Spectre.Console.Cli/Internal/Commands/CompleteCommand.cs

@@ -34,6 +34,8 @@ public sealed class Settings : CommandSettings
 
     public override async Task<int> ExecuteAsync([NotNull] CommandContext context, [NotNull] Settings settings)
     {
+        HighjackConsoles();
+
         var commandToComplete = settings.CommandToComplete;
         if (string.IsNullOrEmpty(commandToComplete))
         {
@@ -372,4 +374,22 @@ private static string TrimOnce(string input, char character)
 
         return input;
     }
+
+    /// <summary>
+    /// Prevents arbitrary consoles from being used by the completion command. (For example, logging consoles).
+    /// </summary>
+    private static void HighjackConsoles()
+    {
+        try
+        {
+            System.Console.Clear();
+        }
+        catch
+        {
+            // Ignored
+        }
+
+        AnsiConsole.Console = new HighjackedAnsiConsole(AnsiConsole.Console);
+        System.Console.SetOut(new HighjackedTextWriter(System.Console.Out));
+    }
 }