Backport PR #13311: Use ThreadPoolExecutor for debugger cmdloop, solving infinite thread-creation and traceback loop

IPython/terminal/debugger.py

@@ -1,159 +1,146 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 create_ipython_shortcuts, 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 concurrent.futures import ThreadPoolExecutor
 
 from prompt_toolkit import __version__ as ptk_version
 PTK3 = ptk_version.startswith('3.')
 
 
 class TerminalPdb(Pdb):
     """Standalone IPython debugger."""
 
     def __init__(self, *args, pt_session_options=None, **kwargs):
         Pdb.__init__(self, *args, **kwargs)
         self._ptcomp = None
         self.pt_init(pt_session_options)
+        self.thread_executor = ThreadPoolExecutor(1)
 
     def pt_init(self, pt_session_options=None):
         """Initialize the prompt session and the prompt loop
         and store them in self.pt_app and self.pt_loop.
         
         Additional keyword arguments for the PromptSession class
         can be specified in pt_session_options.
         """
         if pt_session_options is None:
             pt_session_options = {}
         
         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,
                                        )
             # add a completer for all the do_ methods
             methods_names = [m[3:] for m in dir(self) if m.startswith("do_")]
 
             def gen_comp(self, text):
                 return [m for m in methods_names if m.startswith(text)]
             import types
             newcomp = types.MethodType(gen_comp, compl)
             compl.custom_matchers.insert(0, newcomp)
             # end add completer.
 
             self._ptcomp = IPythonPTCompleter(compl)
 
         options = dict(
             message=(lambda: PygmentsTokens(get_prompt_tokens())),
             editing_mode=getattr(EditingMode, self.shell.editing_mode.upper()),
             key_bindings=create_ipython_shortcuts(self.shell),
             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=getattr(self.shell, "style", None),
             color_depth=self.shell.color_depth,
         )
 
         if not PTK3:
             options['inputhook'] = self.shell.inputhook
         options.update(pt_session_options)
         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 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")
+                print(self.intro, file=self.stdout)
             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
 
                     # Run the prompt in a different thread.
-                    line = ''
-                    keyboard_interrupt = False
-
-                    def in_thread():
-                        nonlocal line, keyboard_interrupt
                         try:
-                            line = self.pt_app.prompt()
+                        line = self.thread_executor.submit(self.pt_app.prompt).result()
                         except EOFError:
-                            line = 'EOF'
-                        except KeyboardInterrupt:
-                            keyboard_interrupt = True
-
-                    th = threading.Thread(target=in_thread)
-                    th.start()
-                    th.join()
+                        line = "EOF"
 
-                    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()