Override console Ctrl+C event handler with handler in module signal (#1951)

* Override console Ctrl+C event handler with handler in module `signal`

* Use nullable annotation

Author: BCSharp

src/core/IronPython.Modules/signal.SimpleSignalState.cs

@@ -14,9 +14,15 @@
 namespace IronPython.Modules {
     public static partial class PythonSignal {
         private class SimpleSignalState : PythonSignalState {
+            private readonly ConsoleCancelEventHandler? _consoleHandler;
 
             public SimpleSignalState(PythonContext pc) : base(pc) {
                 Console.CancelKeyPress += new ConsoleCancelEventHandler(Console_CancelKeyPress);
+                if (pc.Console is Microsoft.Scripting.Hosting.Shell.BasicConsole console) {
+                    // in console hosting scenarios, we need to override the console handler of Ctrl+C
+                    _consoleHandler = console.ConsoleCancelEventHandler;
+                    console.ConsoleCancelEventHandler = null;
+                }
             }
 
 
@@ -42,8 +48,8 @@ private void Console_CancelKeyPress(object? sender, ConsoleCancelEventArgs e) {
                         throw new InvalidOperationException("unreachable");
                     }
                 } else if (ReferenceEquals(handler, default_int_handler) && pySignal == SIGINT) {
-                    // Let the real interrupt handler throw a KeyboardInterrupt for SIGINT.
-                    // It handles this far more gracefully than we can
+                    // Forward the signal to the console handler, if any
+                    _consoleHandler?.Invoke(sender, e);
                     return;
                 } else {
                     CallPythonHandler(pySignal, handler);

src/core/IronPython/Hosting/PythonCommandLine.cs

@@ -145,6 +145,7 @@ protected override void Initialize() {
 
             Console.Output = new OutputWriter(PythonContext, false);
             Console.ErrorOutput = new OutputWriter(PythonContext, true);
+            Language.Console = Console;
 
             // TODO: must precede path initialization! (??? - test test_importpkg.py)
             int pathIndex = PythonContext.PythonOptions.SearchPaths.Count;

src/core/IronPython/Runtime/PythonContext.cs

@@ -22,6 +22,7 @@
 using Microsoft.Scripting.Actions;
 using Microsoft.Scripting.Debugging.CompilerServices;
 using Microsoft.Scripting.Generation;
+using Microsoft.Scripting.Hosting.Shell;
 using Microsoft.Scripting.Runtime;
 using Microsoft.Scripting.Utils;
 
@@ -684,6 +685,15 @@ internal static Version GetPythonVersion()
 
         internal FloatFormat DoubleFormat { get; set; }
 
+#nullable enable
+
+        /// <summary>
+        /// Not null if the Python context is running in a console host.
+        /// </summary>
+        internal IConsole? Console { get; set; }
+
+#nullable restore
+
         /// <summary>
         /// Initializes the sys module on startup.  Called both to load and reload sys
         /// </summary>