Improve REPL KI (#3030)

* improve repl KI

* apply suggestion from review, ensure calls in handler are safe

* grab token and install handler in one go

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Don't add extra newlines on KI

* Add some tests

* First pass at CI failures

* The CI runners have `dev.tty.legacy_tiocsti` set to `0`

This means that we cannot test our usage of `TIOCSTI`. This ctrl+c
support was dead on arrival!

* Hacky fixes for Windows

* Try to avoid flakiness

* Address PR review and first pass at codecov

* Start checking sysctls for `test_ki_newline_injection`

* Try enabling the sysctl

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix pre-commit

* Give up on TIOCSTI in CI

* Actually skip newline injection on Windows

* Actually skip newline injection tests on MacOS

* Codecov annoyances

---------

Co-authored-by: CoolCat467 <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: A5rocks <[email protected]>

Author: 4 people

newsfragments/3007.bugfix.rst

@@ -0,0 +1 @@
+Make ctrl+c work in more situations in the Trio REPL (``python -m trio``).

src/trio/_repl.py

@@ -4,9 +4,10 @@
 import contextlib
 import inspect
 import sys
-import types
 import warnings
 from code import InteractiveConsole
+from types import CodeType, FrameType, FunctionType
+from typing import Callable
 
 import outcome
 
@@ -15,14 +16,33 @@
 from trio._util import final
 
 
+class SuppressDecorator(contextlib.ContextDecorator, contextlib.suppress):
+    pass
+
+
+@SuppressDecorator(KeyboardInterrupt)
+@trio.lowlevel.disable_ki_protection
+def terminal_newline() -> None:  # TODO: test this line
+    import fcntl
+    import termios
+
+    # Fake up a newline char as if user had typed it at the terminal
+    try:
+        fcntl.ioctl(sys.stdin, termios.TIOCSTI, b"\n")  # type: ignore[attr-defined, unused-ignore]
+    except OSError as e:
+        print(f"\nPress enter! Newline injection failed: {e}", end="", flush=True)
+
+
 @final
 class TrioInteractiveConsole(InteractiveConsole):
     def __init__(self, repl_locals: dict[str, object] | None = None) -> None:
         super().__init__(locals=repl_locals)
+        self.token: trio.lowlevel.TrioToken | None = None
         self.compile.compiler.flags |= ast.PyCF_ALLOW_TOP_LEVEL_AWAIT
+        self.interrupted = False
 
-    def runcode(self, code: types.CodeType) -> None:
-        func = types.FunctionType(code, self.locals)
+    def runcode(self, code: CodeType) -> None:
+        func = FunctionType(code, self.locals)
         if inspect.iscoroutinefunction(func):
             result = trio.from_thread.run(outcome.acapture, func)
         else:
@@ -48,6 +68,55 @@ def runcode(self, code: types.CodeType) -> None:
                 # We always use sys.excepthook, unlike other implementations.
                 # This means that overriding self.write also does nothing to tbs.
                 sys.excepthook(sys.last_type, sys.last_value, sys.last_traceback)
+        # clear any residual KI
+        trio.from_thread.run(trio.lowlevel.checkpoint_if_cancelled)
+        # trio.from_thread.check_cancelled() has too long of a memory
+
+    if sys.platform == "win32":  # TODO: test this line
+
+        def raw_input(self, prompt: str = "") -> str:
+            try:
+                return input(prompt)
+            except EOFError:
+                # check if trio has a pending KI
+                trio.from_thread.run(trio.lowlevel.checkpoint_if_cancelled)
+                raise
+
+    else:
+
+        def raw_input(self, prompt: str = "") -> str:
+            from signal import SIGINT, signal
+
+            assert not self.interrupted
+
+            def install_handler() -> (
+                Callable[[int, FrameType | None], None] | int | None
+            ):
+                def handler(
+                    sig: int, frame: FrameType | None
+                ) -> None:  # TODO: test this line
+                    self.interrupted = True
+                    token.run_sync_soon(terminal_newline, idempotent=True)
+
+                token = trio.lowlevel.current_trio_token()
+
+                return signal(SIGINT, handler)
+
+            prev_handler = trio.from_thread.run_sync(install_handler)
+            try:
+                return input(prompt)
+            finally:
+                trio.from_thread.run_sync(signal, SIGINT, prev_handler)
+                if self.interrupted:  # TODO: test this line
+                    raise KeyboardInterrupt
+
+        def write(self, output: str) -> None:
+            if self.interrupted:  # TODO: test this line
+                assert output == "\nKeyboardInterrupt\n"
+                sys.stderr.write(output[1:])
+                self.interrupted = False
+            else:
+                sys.stderr.write(output)
 
 
 async def run_repl(console: TrioInteractiveConsole) -> None:

src/trio/_tests/test_repl.py

@@ -1,7 +1,11 @@
 from __future__ import annotations
 
+import os
+import pathlib
+import signal
 import subprocess
 import sys
+from functools import partial
 from typing import Protocol
 
 import pytest
@@ -239,3 +243,193 @@ def test_main_entrypoint() -> None:
     """
     repl = subprocess.run([sys.executable, "-m", "trio"], input=b"exit()")
     assert repl.returncode == 0
+
+
+def should_try_newline_injection() -> bool:
+    if sys.platform != "linux":
+        return False
+
+    sysctl = pathlib.Path("/proc/sys/dev/tty/legacy_tiocsti")
+    if not sysctl.exists():  # pragma: no cover
+        return True
+
+    else:
+        return sysctl.read_text() == "1"
+
+
+@pytest.mark.skipif(
+    not should_try_newline_injection(),
+    reason="the ioctl we use is disabled in CI",
+)
+def test_ki_newline_injection() -> None:  # TODO: test this line
+    # TODO: we want to remove this functionality, eg by using vendored
+    #       pyrepls.
+    assert sys.platform != "win32"
+
+    import pty
+
+    # NOTE: this cannot be subprocess.Popen because pty.fork
+    #       does some magic to set the controlling terminal.
+    # (which I don't know how to replicate... so I copied this
+    # structure from pty.spawn...)
+    pid, pty_fd = pty.fork()  # type: ignore[attr-defined,unused-ignore]
+    if pid == 0:
+        os.execlp(sys.executable, *[sys.executable, "-u", "-m", "trio"])
+
+    # setup:
+    buffer = b""
+    while not buffer.endswith(b"import trio\r\n>>> "):
+        buffer += os.read(pty_fd, 4096)
+
+    # sanity check:
+    print(buffer.decode())
+    buffer = b""
+    os.write(pty_fd, b'print("hello!")\n')
+    while not buffer.endswith(b">>> "):
+        buffer += os.read(pty_fd, 4096)
+
+    assert buffer.count(b"hello!") == 2
+
+    # press ctrl+c
+    print(buffer.decode())
+    buffer = b""
+    os.kill(pid, signal.SIGINT)
+    while not buffer.endswith(b">>> "):
+        buffer += os.read(pty_fd, 4096)
+
+    assert b"KeyboardInterrupt" in buffer
+
+    # press ctrl+c later
+    print(buffer.decode())
+    buffer = b""
+    os.write(pty_fd, b'print("hello!")')
+    os.kill(pid, signal.SIGINT)
+    while not buffer.endswith(b">>> "):
+        buffer += os.read(pty_fd, 4096)
+
+    assert b"KeyboardInterrupt" in buffer
+    print(buffer.decode())
+    os.close(pty_fd)
+    os.waitpid(pid, 0)[1]
+
+
+async def test_ki_in_repl() -> None:
+    async with trio.open_nursery() as nursery:
+        proc = await nursery.start(
+            partial(
+                trio.run_process,
+                [sys.executable, "-u", "-m", "trio"],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.STDOUT,
+                stdin=subprocess.PIPE,
+                creationflags=subprocess.CREATE_NEW_PROCESS_GROUP if sys.platform == "win32" else 0,  # type: ignore[attr-defined,unused-ignore]
+            )
+        )
+
+        async with proc.stdout:
+            # setup
+            buffer = b""
+            async for part in proc.stdout:  # pragma: no branch
+                buffer += part
+                # TODO: consider making run_process stdout have some universal newlines thing
+                if buffer.replace(b"\r\n", b"\n").endswith(b"import trio\n>>> "):
+                    break
+
+            # ensure things work
+            print(buffer.decode())
+            buffer = b""
+            await proc.stdin.send_all(b'print("hello!")\n')
+            async for part in proc.stdout:  # pragma: no branch
+                buffer += part
+                if buffer.endswith(b">>> "):
+                    break
+
+            assert b"hello!" in buffer
+            print(buffer.decode())
+
+            # this seems to be necessary on Windows for reasons
+            # (the parents of process groups ignore ctrl+c by default...)
+            if sys.platform == "win32":
+                buffer = b""
+                await proc.stdin.send_all(
+                    b"import ctypes; ctypes.windll.kernel32.SetConsoleCtrlHandler(None, False)\n"
+                )
+                async for part in proc.stdout:  # pragma: no branch
+                    buffer += part
+                    if buffer.endswith(b">>> "):
+                        break
+
+                print(buffer.decode())
+
+            # try to decrease flakiness...
+            buffer = b""
+            await proc.stdin.send_all(
+                b"import coverage; trio.lowlevel.enable_ki_protection(coverage.pytracer.PyTracer._trace)\n"
+            )
+            async for part in proc.stdout:  # pragma: no branch
+                buffer += part
+                if buffer.endswith(b">>> "):
+                    break
+
+            print(buffer.decode())
+
+            # ensure that ctrl+c on a prompt works
+            # NOTE: for some reason, signal.SIGINT doesn't work for this test.
+            # Using CTRL_C_EVENT is also why we need subprocess.CREATE_NEW_PROCESS_GROUP
+            signal_sent = signal.CTRL_C_EVENT if sys.platform == "win32" else signal.SIGINT  # type: ignore[attr-defined,unused-ignore]
+            os.kill(proc.pid, signal_sent)
+            if sys.platform == "win32":
+                # we rely on EOFError which... doesn't happen with pipes.
+                # I'm not sure how to fix it...
+                await proc.stdin.send_all(b"\n")
+            else:
+                # we test injection separately
+                await proc.stdin.send_all(b"\n")
+
+            buffer = b""
+            async for part in proc.stdout:  # pragma: no branch
+                buffer += part
+                if buffer.endswith(b">>> "):
+                    break
+
+            assert b"KeyboardInterrupt" in buffer
+
+            # ensure ctrl+c while a command runs works
+            print(buffer.decode())
+            await proc.stdin.send_all(b'print("READY"); await trio.sleep_forever()\n')
+            killed = False
+            buffer = b""
+            async for part in proc.stdout:  # pragma: no branch
+                buffer += part
+                if buffer.replace(b"\r\n", b"\n").endswith(b"READY\n") and not killed:
+                    os.kill(proc.pid, signal_sent)
+                    killed = True
+                if buffer.endswith(b">>> "):
+                    break
+
+            assert b"trio" in buffer
+            assert b"KeyboardInterrupt" in buffer
+
+            # make sure it works for sync commands too
+            # (though this would be hard to break)
+            print(buffer.decode())
+            await proc.stdin.send_all(
+                b'import time; print("READY"); time.sleep(99999)\n'
+            )
+            killed = False
+            buffer = b""
+            async for part in proc.stdout:  # pragma: no branch
+                buffer += part
+                if buffer.replace(b"\r\n", b"\n").endswith(b"READY\n") and not killed:
+                    os.kill(proc.pid, signal_sent)
+                    killed = True
+                if buffer.endswith(b">>> "):
+                    break
+
+            assert b"Traceback" in buffer
+            assert b"KeyboardInterrupt" in buffer
+
+            print(buffer.decode())
+
+        # kill the process
+        nursery.cancel_scope.cancel()