Add test showing issue with child in tty lock when cancelled

examples/debugging/root_cancelled_but_child_is_in_tty_lock.py

@@ -0,0 +1,48 @@
+import tractor
+
+
+async def name_error():
+    "Raise a ``NameError``"
+    getattr(doggypants)
+
+
+async def spawn_until(depth=0):
+    """"A nested nursery that triggers another ``NameError``.
+    """
+    async with tractor.open_nursery() as n:
+        if depth < 1:
+            # await n.run_in_actor('breakpoint_forever', breakpoint_forever)
+            await n.run_in_actor('name_error', name_error)
+        else:
+            depth -= 1
+            await n.run_in_actor(f'spawn_until_{depth}', spawn_until, depth=depth)
+
+
+async def main():
+    """The main ``tractor`` routine.
+
+    The process tree should look as approximately as follows when the debugger
+    first engages:
+
+    python examples/debugging/multi_nested_subactors_bp_forever.py
+    ├─ python -m tractor._child --uid ('spawner1', '7eab8462 ...)
+    │  └─ python -m tractor._child --uid ('spawn_until_0', '3720602b ...)
+    │     └─ python -m tractor._child --uid ('name_error', '505bf71d ...)
+    │
+    └─ python -m tractor._child --uid ('spawner0', '1d42012b ...)
+       └─ python -m tractor._child --uid ('name_error', '6c2733b8 ...)
+
+    """
+    async with tractor.open_nursery() as n:
+
+        # spawn both actors
+        portal = await n.run_in_actor('spawner0', spawn_until, depth=0)
+        portal1 = await n.run_in_actor('spawner1', spawn_until, depth=1)
+
+        # nursery cancellation should be triggered due to propagated error
+        await portal.result()
+        await portal1.result()
+
+
+if __name__ == '__main__':
+    tractor.run(main, debug_mode=True, loglevel='trace')

tests/test_debugger.py

@@ -331,3 +331,16 @@ def test_multi_nested_subactors_error_through_nurseries(spawn):
 
     before = str(child.before.decode())
     assert "NameError" in before
+
+
+def test_root_nursery_cancels_before_child_releases_tty_lock(spawn):
+    """Exemplifies a bug where the root sends a cancel message before a nested child
+    which has the tty lock (and is in pdb) doesn't cancel after exiting the debugger.
+    """
+    child = spawn('root_cancelled_but_child_is_in_tty_lock')
+
+    for _ in range(5):
+        child.expect(r"\(Pdb\+\+\)")
+        child.sendline('c')
+
+    # child.expect(pexpect.EOF)