End the `pdb` SIGINT handling madness

Turns out this is a lower level issue in terms of the stdlib's default
`pdb.Pdb` settings and how they conflict with `trio`s cancellation and
KBI handling. The details are hashed out more thoroughly in
python-trio/trio#1155. Maybe we can get a fix in trio so things are
solved under our feet :)

tractor/__init__.py

@@ -117,9 +117,13 @@ async def _main(
     # Note that if the current actor is the arbiter it is desirable
     # for it to stay up indefinitely until a re-election process has
     # taken place - which is not implemented yet FYI).
+
+    try:
         return await _start_actor(
             actor, main, host, port, arbiter_addr=arbiter_addr
         )
+    finally:
+        logger.info("Root actor terminated")
 
 
 def run(

tractor/_actor.py

@@ -767,8 +767,8 @@ class Actor:
         finally:
             log.info("Root nursery complete")
 
-            # tear down all lifetime contexts
-            # api idea: ``tractor.open_context()``
+            # tear down all lifetime contexts if not in guest mode
+            # XXX: should this just be in the entrypoint?
             log.warning("Closing all actor lifetime contexts")
             self._lifetime_stack.close()
 

tractor/_debug.py

@@ -6,12 +6,10 @@ import sys
 from functools import partial
 from contextlib import asynccontextmanager
 from typing import Awaitable, Tuple, Optional, Callable, AsyncIterator
-# import signal
 
 from async_generator import aclosing
 import tractor
 import trio
-from trio.testing import wait_all_tasks_blocked
 
 from .log import get_logger
 from . import _state
@@ -132,19 +130,6 @@ async def _acquire_debug_lock(uid: Tuple[str, str]) -> AsyncIterator[None]:
         log.error(f"TTY lock released by {task_name}:{uid}")
 
 
-def handler(signum, frame):
-    """Block SIGINT while in debug to avoid deadlocks with cancellation.
-    """
-    print(
-        "tractor ignores SIGINT while in debug mode\n"
-        "If you have a special need for it please open an issue.\n"
-    )
-
-
-# don't allow those stdlib mofos to mess with sigint handler
-pdbpp.pdb.Pdb.sigint_handler = handler
-
-
 # @contextmanager
 # def _disable_sigint():
 #     try:
@@ -269,14 +254,29 @@ def _breakpoint(debug_func) -> Awaitable[None]:
         log.debug("Entering the synchronous world of pdb")
         debug_func(actor)
 
-
     # user code **must** await this!
     return _bp()
 
 
+def _mk_pdb():
+    # XXX: setting these flags on the pdb instance are absolutely
+    # critical to having ctrl-c work in the ``trio`` standard way!
+    # The stdlib's pdb supports entering the current sync frame
+    # on a SIGINT, with ``trio`` we pretty much never want this
+    # and we did we can handle it in the ``tractor`` task runtime.
+
+    pdb = PdbwTeardown()
+    pdb.allow_kbdint = True
+    pdb.nosigint = True
+
+    return pdb
+
+
 def _set_trace(actor):
     log.critical(f"\nAttaching pdb to actor: {actor.uid}\n")
-    PdbwTeardown().set_trace(
+
+    pdb = _mk_pdb()
+    pdb.set_trace(
         # start 2 levels up in user code
         frame=sys._getframe().f_back.f_back,
     )
@@ -290,8 +290,10 @@ breakpoint = partial(
 
 def _post_mortem(actor):
     log.critical(f"\nAttaching to pdb in crashed actor: {actor.uid}\n")
+    pdb = _mk_pdb()
+
     # custom Pdb post-mortem entry
-    pdbpp.xpm(Pdb=PdbwTeardown)
+    pdbpp.xpm(Pdb=lambda: pdb)
 
 
 post_mortem = partial(

tractor/_entry.py

@@ -7,7 +7,6 @@ import signal
 
 import trio  # type: ignore
 
-from ._actor import Actor
 from .log import get_console_log, get_logger
 from . import _state
 
@@ -16,7 +15,7 @@ log = get_logger(__name__)
 
 
 def _mp_main(
-    actor: 'Actor',
+    actor: 'Actor',  # noqa
     accept_addr: Tuple[str, int],
     forkserver_info: Tuple[Any, Any, Any, Any, Any],
     start_method: str,
@@ -49,11 +48,13 @@ def _mp_main(
         trio.run(trio_main)
     except KeyboardInterrupt:
         pass  # handle it the same way trio does?
+
+    finally:
         log.info(f"Actor {actor.uid} terminated")
 
 
 def _trio_main(
-    actor: 'Actor',
+    actor: 'Actor',  # noqa
     parent_addr: Tuple[str, int] = None
 ) -> None:
     """Entry point for a `trio_run_in_process` subactor.
@@ -86,4 +87,5 @@ def _trio_main(
     except KeyboardInterrupt:
         log.warning(f"Actor {actor.uid} received KBI")
 
+    finally:
         log.info(f"Actor {actor.uid} terminated")