Add two-stage Ctrl+C cancellation UX (#5345)

src/Platform/Microsoft.Testing.Platform/OutputDevice/SimplifiedConsoleOutputDeviceBase.cs

@@ -85,6 +85,7 @@ public async Task InitializeAsync()
             () =>
             {
                 ConsoleLog(PlatformResources.CancellingTestSession);
+                ConsoleLog(PlatformResources.PressCtrlCAgainToForceExit);
                 return Task.CompletedTask;
             }).ConfigureAwait(false);
 

src/Platform/Microsoft.Testing.Platform/OutputDevice/Terminal/TerminalTestReporter.cs

@@ -167,6 +167,7 @@ public void StartCancelling()
         {
             terminal.AppendLine();
             terminal.AppendLine(PlatformResources.CancellingTestSession);
+            terminal.AppendLine(PlatformResources.PressCtrlCAgainToForceExit);
             terminal.AppendLine();
         });
     }

src/Platform/Microsoft.Testing.Platform/OutputDevice/TerminalOutputDevice.cs

@@ -127,7 +127,11 @@ public async Task InitializeAsync()
             // stdout, corrupting the JSON document. Route a single-line cancellation notice
             // to stderr instead so the user still gets feedback on Ctrl+C.
             await _policiesService.RegisterOnAbortCallbackAsync(
-                () => WriteToStandardErrorAsync(PlatformResources.CancellingTestSession)).ConfigureAwait(false);
+                async () =>
+                {
+                    await WriteToStandardErrorAsync(PlatformResources.CancellingTestSession).ConfigureAwait(false);
+                    await WriteToStandardErrorAsync(PlatformResources.PressCtrlCAgainToForceExit).ConfigureAwait(false);
+                }).ConfigureAwait(false);
         }
         else
         {

src/Platform/Microsoft.Testing.Platform/Resources/PlatformResources.resx

@@ -522,6 +522,9 @@ Read more about Microsoft Testing Platform telemetry: https://aka.ms/testingplat
   <data name="CancellingTestSession" xml:space="preserve">
     <value>Canceling the test session...</value>
   </data>
+  <data name="PressCtrlCAgainToForceExit" xml:space="preserve">
+    <value>Press Ctrl+C again to force exit.</value>
+  </data>
   <data name="DiagnosticFileLevelWithAsyncFlush" xml:space="preserve">
     <value>Diagnostic file (level '{0}' with async flush): {1}</value>
     <comment>0 level such as verbose,

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.cs.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Může mít jenom jeden argument jako řetězec ve formátu &lt;value&gt;[h|m|s], kde value je hodnota datového typu float.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">Proces měl být ukončen před tím, než jsme mohli určit tuto hodnotu.</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.de.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Nimmt ein Argument als Zeichenfolge im Format &lt;value&gt;[h|m|s], wobei "value" auf "float" festgelegt ist.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">Der Prozess hätte beendet werden müssen, bevor dieser Wert ermittelt werden kann</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.es.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Toma un argumento como cadena con el formato &lt;value&gt;[h|m|s] donde 'value' es float.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">El proceso debería haberse terminado para poder determinar este valor</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.fr.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Prend un argument sous forme de chaîne au format &lt;value&gt;[h|m|s] où « value » est float.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">Le processus aurait dû s’arrêter avant que nous puissions déterminer cette valeur</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.it.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Acquisisce un argomento come stringa nel formato &lt;value&gt;[h|m|s] dove 'value' è float.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">Il processo dovrebbe essere terminato prima di poter determinare questo valore</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.ja.xlf

@@ -686,6 +686,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 1 つの引数を文字列として &lt;value&gt;[h|m|s] の形式で使用します。この場合、'value' は float です。</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">この値を決定する前にプロセスを終了する必要があります</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.ko.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 'value'가 float인 &lt;value&gt;[h|m|s] 형식의 문자열로 인수 하나를 사용합니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">이 값을 결정하려면 프로세스가 종료되어야 합니다.</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.pl.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Pobiera jeden argument jako ciąg w formacie &lt;value&gt;[h|m|s], gdzie element „value” ma wartość zmiennoprzecinkową.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">Proces powinien zakończyć się przed ustaleniem tej wartości</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.pt-BR.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Recebe um argumento como cadeia de caracteres no formato &lt;valor&gt;[h|m|s] em que 'valor' é float.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">O processo deve ter sido encerrado antes que possamos determinar esse valor</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.ru.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Принимает один аргумент в виде строки в формате &lt;value&gt;[h|m|s], где "value" — число с плавающей точкой.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">Процесс должен быть завершен, прежде чем мы сможем определить это значение</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.tr.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 Bir bağımsız değişkeni, 'value' değerinin kayan olduğu &lt;value&gt;[h|m|s] biçiminde dize olarak alır.</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">Bu değeri belirleyebilmemiz için süreçten çıkılmış olması gerekir</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.zh-Hans.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 获取一个字符串形式的参数，格式为 &lt;value&gt;[h|m|s]，其中 "value" 为浮点型。</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">在我们确定此值之前，流程应该已退出</target>

src/Platform/Microsoft.Testing.Platform/Resources/xlf/PlatformResources.zh-Hant.xlf

@@ -685,6 +685,11 @@ Takes one argument as string in the format <value>[h|m|s] where 'value' is
 將一個引數作為字串，格式為 &lt;value&gt;[h|m|s]，其中 'value' 為 float。</target>
         <note />
       </trans-unit>
+      <trans-unit id="PressCtrlCAgainToForceExit">
+        <source>Press Ctrl+C again to force exit.</source>
+        <target state="new">Press Ctrl+C again to force exit.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ProcessHasNotYetExitedErrorMessage">
         <source>Process should have exited before we can determine this value</source>
         <target state="translated">在我們確定此值之前，流程應已結束</target>

src/Platform/Microsoft.Testing.Platform/Services/CTRLPlusCCancellationTokenSource.cs

@@ -8,16 +8,26 @@ namespace Microsoft.Testing.Platform.Services;
 
 internal sealed class CTRLPlusCCancellationTokenSource : ITestApplicationCancellationTokenSource, IDisposable
 {
+    private const int StateIdle = 0;
+    private const int StateCancelling = 1;
+    private const int StateForcing = 2;
+
     private readonly CancellationTokenSource _cancellationTokenSource = new();
+    private readonly IEnvironment _environment;
     private readonly ILogger? _logger;
+    private readonly IConsole? _subscribedConsole;
+    private int _state = StateIdle;
+    private int _disposed;
 
-    public CTRLPlusCCancellationTokenSource(IConsole? console = null, ILogger? logger = null)
+    public CTRLPlusCCancellationTokenSource(IConsole? console = null, ILogger? logger = null, IEnvironment? environment = null)
     {
         if (console is not null && !IsCancelKeyPressNotSupported())
         {
             console.CancelKeyPress += OnConsoleCancelKeyPressed;
+            _subscribedConsole = console;
         }
 
+        _environment = environment ?? new SystemEnvironment();
         _logger = logger;
     }
 
@@ -40,19 +50,60 @@ public CancellationToken CancellationToken
 
     private void OnConsoleCancelKeyPressed(object? sender, ConsoleCancelEventArgs e)
     {
+        // Suppress the runtime's default Ctrl+C handling so we control the exit code on
+        // both the first (cooperative) and the second (force-exit) press.
         e.Cancel = true;
-        try
+
+        // The state machine counts user Ctrl+C presses *independently* of external cancellation
+        // sources (timeout, max-failed-tests, explicit Cancel()). This honors the contract
+        // advertised next to the "Cancelling..." message ("Press Ctrl+C again to force exit.")
+        // regardless of who initiated the cancellation: the user must always press Ctrl+C twice
+        // to force-exit.
+        if (Interlocked.CompareExchange(ref _state, StateCancelling, StateIdle) == StateIdle)
         {
-            _cancellationTokenSource.Cancel();
+            // First user Ctrl+C: cooperative cancellation. If the token was already cancelled
+            // by an external source this is effectively a no-op, but we still transitioned the
+            // state so the next press goes to force-exit.
+            try
+            {
+                _cancellationTokenSource.Cancel();
+            }
+            catch (AggregateException ex)
+            {
+                _logger?.LogWarning($"Exception during CTRLPlusCCancellationTokenSource cancel:\n{ex}");
+            }
+
+            return;
         }
-        catch (AggregateException ex)
+
+        // Second user Ctrl+C: force-exit. We intentionally do not print an extra
+        // "Forcing exit..." message here because the IConsole abstraction has no stderr channel
+        // and writing to stdout would corrupt the JSON document produced by --list-tests json.
+        // The user already saw the "Press Ctrl+C again to force exit." hint, so the exit itself
+        // is the confirmation. Any subsequent presses are suppressed by the StateForcing guard.
+        if (Interlocked.CompareExchange(ref _state, StateForcing, StateCancelling) == StateCancelling)
         {
-            _logger?.LogWarning($"Exception during CTRLPlusCCancellationTokenSource cancel:\n{ex}");
+            _environment.Exit((int)ExitCode.TestSessionAborted);
         }
     }
 
     public void Dispose()
-        => _cancellationTokenSource.Dispose();
+    {
+        if (Interlocked.Exchange(ref _disposed, 1) != 0)
+        {
+            return;
+        }
+
+        // We stored the console reference only when subscription was actually performed
+        // (i.e. when CancelKeyPress is supported on this platform), so we can safely call -=
+        // on the same supported-platform paths.
+        if (_subscribedConsole is not null && !IsCancelKeyPressNotSupported())
+        {
+            _subscribedConsole.CancelKeyPress -= OnConsoleCancelKeyPressed;
+        }
+
+        _cancellationTokenSource.Dispose();
+    }
 
     public void Cancel()
         => _cancellationTokenSource.Cancel();