Backport PR #12141: Run ipdb in separate thread (required when using within asyncio applications).

IPython/terminal/debugger.py

@@ -1,147 +1,152 b''
 import asyncio
 import signal
 import sys
+import threading
 
 from IPython.core.debugger import Pdb
 
 from IPython.core.completer import IPCompleter
 from .ptutils import IPythonPTCompleter
 from .shortcuts import suspend_to_bg, cursor_in_leading_ws
 
 from prompt_toolkit.enums import DEFAULT_BUFFER
 from prompt_toolkit.filters import (Condition, has_focus, has_selection,
     vi_insert_mode, emacs_insert_mode)
 from prompt_toolkit.key_binding import KeyBindings
 from prompt_toolkit.key_binding.bindings.completion import display_completions_like_readline
 from pygments.token import Token
 from prompt_toolkit.shortcuts.prompt import PromptSession
 from prompt_toolkit.enums import EditingMode
 from prompt_toolkit.formatted_text import PygmentsTokens
 
 from prompt_toolkit import __version__ as ptk_version
 PTK3 = ptk_version.startswith('3.')
 
 
 class TerminalPdb(Pdb):
     """Standalone IPython debugger."""
 
     def __init__(self, *args, **kwargs):
         Pdb.__init__(self, *args, **kwargs)
         self._ptcomp = None
         self.pt_init()
 
     def pt_init(self):
         def get_prompt_tokens():
             return [(Token.Prompt, self.prompt)]
 
         if self._ptcomp is None:
             compl = IPCompleter(shell=self.shell,
                                         namespace={},
                                         global_namespace={},
                                         parent=self.shell,
                                        )
             self._ptcomp = IPythonPTCompleter(compl)
 
         kb = KeyBindings()
         supports_suspend = Condition(lambda: hasattr(signal, 'SIGTSTP'))
         kb.add('c-z', filter=supports_suspend)(suspend_to_bg)
 
         if self.shell.display_completions == 'readlinelike':
             kb.add('tab', filter=(has_focus(DEFAULT_BUFFER)
                                   & ~has_selection
                                   & vi_insert_mode | emacs_insert_mode
                                   & ~cursor_in_leading_ws
                               ))(display_completions_like_readline)
 
         options = dict(
             message=(lambda: PygmentsTokens(get_prompt_tokens())),
             editing_mode=getattr(EditingMode, self.shell.editing_mode.upper()),
             key_bindings=kb,
             history=self.shell.debugger_history,
             completer=self._ptcomp,
             enable_history_search=True,
             mouse_support=self.shell.mouse_support,
             complete_style=self.shell.pt_complete_style,
             style=self.shell.style,
             color_depth=self.shell.color_depth,
         )
 
         if not PTK3:
             options['inputhook'] = self.shell.inputhook
         self.pt_loop = asyncio.new_event_loop()
         self.pt_app = PromptSession(**options)
 
     def cmdloop(self, intro=None):
         """Repeatedly issue a prompt, accept input, parse an initial prefix
         off the received input, and dispatch to action methods, passing them
         the remainder of the line as argument.
 
         override the same methods from cmd.Cmd to provide prompt toolkit replacement.
         """
         if not self.use_rawinput:
             raise ValueError('Sorry ipdb does not support use_rawinput=False')
 
-        # In order to make sure that asyncio code written in the
-        # interactive shell doesn't interfere with the prompt, we run the
-        # prompt in a different event loop.
-        # If we don't do this, people could spawn coroutine with a
-        # while/true inside which will freeze the prompt.
-
-        try:
-            old_loop = asyncio.get_event_loop()
-        except RuntimeError:
-            # This happens when the user used `asyncio.run()`.
-            old_loop = None
-
+        # In order to make sure that prompt, which uses asyncio doesn't
+        # interfere with applications in which it's used, we always run the
+        # prompt itself in a different thread (we can't start an event loop
+        # within an event loop). This new thread won't have any event loop
+        # running, and here we run our prompt-loop.
 
         self.preloop()
 
         try:
             if intro is not None:
                 self.intro = intro
             if self.intro:
                 self.stdout.write(str(self.intro)+"\n")
             stop = None
             while not stop:
                 if self.cmdqueue:
                     line = self.cmdqueue.pop(0)
                 else:
                     self._ptcomp.ipy_completer.namespace = self.curframe_locals
                     self._ptcomp.ipy_completer.global_namespace = self.curframe.f_globals
 
-                    asyncio.set_event_loop(self.pt_loop)
-                    try:
-                        line = self.pt_app.prompt()
-                    except EOFError:
-                        line = 'EOF'
-                    finally:
-                        # Restore the original event loop.
-                        asyncio.set_event_loop(old_loop)
+                    # Run the prompt in a different thread.
+                    line = ''
+                    keyboard_interrupt = False
+
+                    def in_thread():
+                        nonlocal line, keyboard_interrupt
+                        try:
+                            line = self.pt_app.prompt()
+                        except EOFError:
+                            line = 'EOF'
+                        except KeyboardInterrupt:
+                            keyboard_interrupt = True
+
+                    th = threading.Thread(target=in_thread)
+                    th.start()
+                    th.join()
+
+                    if keyboard_interrupt:
+                        raise KeyboardInterrupt
 
                 line = self.precmd(line)
                 stop = self.onecmd(line)
                 stop = self.postcmd(stop, line)
             self.postloop()
         except Exception:
             raise
 
 
 def set_trace(frame=None):
     """
     Start debugging from `frame`.
 
     If frame is not specified, debugging starts from caller's frame.
     """
     TerminalPdb().set_trace(frame or sys._getframe().f_back)
 
 
 if __name__ == '__main__':
     import pdb
     # IPython.core.debugger.Pdb.trace_dispatch shall not catch
     # bdb.BdbQuit. When started through __main__ and an exception
     # happened after hitting "c", this is needed in order to
     # be able to quit the debugging session (see #9950).
     old_trace_dispatch = pdb.Pdb.trace_dispatch
     pdb.Pdb = TerminalPdb
     pdb.Pdb.trace_dispatch = old_trace_dispatch
     pdb.main()