Merge pull request #490 from itamarst/10516-pdb-freezes

Make pdb on Windows interruptible

ipykernel/kernelapp.py

@@ -539,13 +539,28 @@ def _init_asyncio_patch(self):
                     # fallback to the pre-3.8 default of Selector
                     asyncio.set_event_loop_policy(WindowsSelectorEventLoopPolicy())
 
+    def init_pdb(self):
+        """Replace pdb with IPython's version that is interruptible.
+        
+        With the non-interruptible version, stopping pdb() locks up the kernel in a
+        non-recoverable state.
+        """
+        import pdb
+        from IPython.core import debugger
+        if hasattr(debugger, "InterruptiblePdb"):
+            # Only available in newer IPython releases:
+            debugger.Pdb = debugger.InterruptiblePdb
+            pdb.Pdb = debugger.Pdb
+            pdb.set_trace = debugger.set_trace
+
     @catch_config_error
     def initialize(self, argv=None):
         self._init_asyncio_patch()
         super(IPKernelApp, self).initialize(argv)
         if self.subapp is not None:
             return
 
+        self.init_pdb()
         self.init_blackhole()
         self.init_connection_file()
         self.init_poller()

ipykernel/tests/test_kernel.py

@@ -12,8 +12,11 @@
 
 import nose.tools as nt
 from flaky import flaky
+import pytest
+from packaging import version
 
 from IPython.testing import decorators as dec, tools as tt
+import IPython
 from ipython_genutils import py3compat
 from IPython.paths import locate_profile
 from ipython_genutils.tempdir import TemporaryDirectory
@@ -379,3 +382,30 @@ def test_interrupt_during_input():
         reply = kc.get_shell_msg(timeout=TIMEOUT)
         from .test_message_spec import validate_message
         validate_message(reply, 'execute_reply', msg_id)
+
+
+@pytest.mark.skipif(
+    version.parse(IPython.__version__) < version.parse("7.14.0"),
+    reason="Need new IPython"
+)
+def test_interrupt_during_pdb_set_trace():
+    """
+    The kernel exits after being interrupted while waiting in pdb.set_trace().
+
+    Merely testing input() isn't enough, pdb has its own issues that need
+    to be handled in addition.
+
+    This test will fail with versions of IPython < 7.14.0.
+    """
+    with new_kernel() as kc:
+        km = kc.parent
+        msg_id = kc.execute("import pdb; pdb.set_trace()")
+        msg_id2 = kc.execute("3 + 4")
+        time.sleep(1)  # Make sure it's actually waiting for input.
+        km.interrupt_kernel()
+        # If we failed to interrupt interrupt, this will timeout:
+        from .test_message_spec import validate_message
+        reply = kc.get_shell_msg(timeout=TIMEOUT)
+        validate_message(reply, 'execute_reply', msg_id)
+        reply = kc.get_shell_msg(timeout=TIMEOUT)
+        validate_message(reply, 'execute_reply', msg_id2)