[3.13] gh-120221: Support KeyboardInterrupt in asyncio REPL (GH-123795) (#123799)

This switches the main pyrepl event loop to always be non-blocking so that it
can listen to incoming interruptions from other threads.

This also resolves invalid display of exceptions from other threads
(gh-123178).

This also fixes freezes with pasting and an active input hook.
(cherry picked from commit 033510e11dff742d9626b9fd895925ac77f566f1)

Co-authored-by: Łukasz Langa <lukasz@langa.pl>

1 files changed, 74 insertions, 0 deletions

diff --git a/Lib/_pyrepl/_threading_handler.py b/Lib/_pyrepl/_threading_handler.py
new file mode 100644
index 0000000..82f5e86
--- /dev/null
+++ b/Lib/_pyrepl/_threading_handler.py
@@ -0,0 +1,74 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+import traceback
+
+
+TYPE_CHECKING = False
+if TYPE_CHECKING:
+    from threading import Thread
+    from types import TracebackType
+    from typing import Protocol
+
+    class ExceptHookArgs(Protocol):
+        @property
+        def exc_type(self) -> type[BaseException]: ...
+        @property
+        def exc_value(self) -> BaseException | None: ...
+        @property
+        def exc_traceback(self) -> TracebackType | None: ...
+        @property
+        def thread(self) -> Thread | None: ...
+
+    class ShowExceptions(Protocol):
+        def __call__(self) -> int: ...
+        def add(self, s: str) -> None: ...
+
+    from .reader import Reader
+
+
+def install_threading_hook(reader: Reader) -> None:
+    import threading
+
+    @dataclass
+    class ExceptHookHandler:
+        lock: threading.Lock = field(default_factory=threading.Lock)
+        messages: list[str] = field(default_factory=list)
+
+        def show(self) -> int:
+            count = 0
+            with self.lock:
+                if not self.messages:
+                    return 0
+                reader.restore()
+                for tb in self.messages:
+                    count += 1
+                    if tb:
+                        print(tb)
+                self.messages.clear()
+                reader.scheduled_commands.append("ctrl-c")
+                reader.prepare()
+            return count
+
+        def add(self, s: str) -> None:
+            with self.lock:
+                self.messages.append(s)
+
+        def exception(self, args: ExceptHookArgs) -> None:
+            lines = traceback.format_exception(
+                args.exc_type,
+                args.exc_value,
+                args.exc_traceback,
+                colorize=reader.can_colorize,
+            )  # type: ignore[call-overload]
+            pre = f"\nException in {args.thread.name}:\n" if args.thread else "\n"
+            tb = pre + "".join(lines)
+            self.add(tb)
+
+        def __call__(self) -> int:
+            return self.show()
+
+
+    handler = ExceptHookHandler()
+    reader.threading_hook = handler
+    threading.excepthook = handler.exception