Use prompt_toolkit.application.create_app_session for debugger prompt

Running the debugger prompt in the default prompt_toolkit session causes issues when more than one prompt_toolkit app is running simultaneously. The errors look exactly like those mentioned in  #12192. This commit solves this by using the dedicated API from prompt_toolkit.

IPython/terminal/debugger.py

@@ -1,178 +1,188 b''
 import asyncio
 import os
 import sys
 
 from IPython.core.debugger import Pdb
 from IPython.core.completer import IPCompleter
 from .ptutils import IPythonPTCompleter
 from .shortcuts import create_ipython_shortcuts
 from . import embed
 
 from pathlib import Path
 from pygments.token import Token
+from prompt_toolkit.application import create_app_session
 from prompt_toolkit.shortcuts.prompt import PromptSession
 from prompt_toolkit.enums import EditingMode
 from prompt_toolkit.formatted_text import PygmentsTokens
 from prompt_toolkit.history import InMemoryHistory, FileHistory
 from concurrent.futures import ThreadPoolExecutor
 
 from prompt_toolkit import __version__ as ptk_version
 PTK3 = ptk_version.startswith('3.')
 
 
 # we want to avoid ptk as much as possible when using subprocesses
 # as it uses cursor positioning requests, deletes color ....
 _use_simple_prompt = "IPY_TEST_SIMPLE_PROMPT" in os.environ
 
 
 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)
 
         # setup history only when we start pdb
         if self.shell.debugger_history is None:
             if self.shell.debugger_history_file is not None:
 
                 p = Path(self.shell.debugger_history_file).expanduser()
                 if not p.exists():
                     p.touch()
                 self.debugger_history = FileHistory(os.path.expanduser(str(p)))
             else:
                 self.debugger_history = InMemoryHistory()
         else:
             self.debugger_history = self.shell.debugger_history
 
         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.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)
         if not _use_simple_prompt:
             self.pt_loop = asyncio.new_event_loop()
             self.pt_app = PromptSession(**options)
 
+    def _prompt(self):
+        """
+        In case another prompt_toolkit apps have to run in parallel to this one (e.g. in madbg),
+        create_app_session must be used to prevent mixing up between them. According to the prompt_toolkit docs:
+
+        If you need multiple applications running at the same time, you have to create a separate
+        `AppSession` using a `with create_app_session():` block.
+        """
+        with create_app_session():
+            return self.pt_app.prompt()
+
     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:
                 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.
                     if not _use_simple_prompt:
                         try:
-                            line = self.thread_executor.submit(
-                                self.pt_app.prompt
-                            ).result()
+                            line = self.thread_executor.submit(self._prompt).result()
                         except EOFError:
                             line = "EOF"
                     else:
                         line = input("ipdb> ")
 
                 line = self.precmd(line)
                 stop = self.onecmd(line)
                 stop = self.postcmd(stop, line)
             self.postloop()
         except Exception:
             raise
 
     def do_interact(self, arg):
         ipshell = embed.InteractiveShellEmbed(
             config=self.shell.config,
             banner1="*interactive*",
             exit_msg="*exiting interactive console...*",
         )
         global_ns = self.curframe.f_globals
         ipshell(
             module=sys.modules.get(global_ns["__name__"], None),
             local_ns=self.curframe_locals,
         )
 
 
 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  # type: ignore
     pdb.Pdb.trace_dispatch = old_trace_dispatch  # type: ignore
     pdb.main()