ipdb: accept header= argument (#14289)

This improves symmetry between Ipdb and vanilla old Pdb.

The `header` argument to `pdb.set_trace()` [has been added in Python
3.7](https://docs.python.org/3.9/whatsnew/3.7.html#pdb).

_(This still requires changes in
[gotcha/ipdb](https://github.com/gotcha/ipdb) to be fully useful - I'll
get to that later :wink:)_

IPython/core/debugger.py

@@ -1,1120 +1,1123 b''
 # -*- coding: utf-8 -*-
 """
 Pdb debugger class.
 
 
 This is an extension to PDB which adds a number of new features.
 Note that there is also the `IPython.terminal.debugger` class which provides UI
 improvements.
 
 We also strongly recommend to use this via the `ipdb` package, which provides
 extra configuration options.
 
 Among other things, this subclass of PDB:
  - supports many IPython magics like pdef/psource
  - hide frames in tracebacks based on `__tracebackhide__`
  - allows to skip frames based on `__debuggerskip__`
 
 The skipping and hiding frames are configurable via the `skip_predicates`
 command.
 
 By default, frames from readonly files will be hidden, frames containing
 ``__tracebackhide__=True`` will be hidden.
 
 Frames containing ``__debuggerskip__`` will be stepped over, frames who's parent
 frames value of ``__debuggerskip__`` is ``True`` will be skipped.
 
     >>> def helpers_helper():
     ...     pass
     ...
     ... def helper_1():
     ...     print("don't step in me")
     ...     helpers_helpers() # will be stepped over unless breakpoint set.
     ...
     ...
     ... def helper_2():
     ...     print("in me neither")
     ...
 
 One can define a decorator that wraps a function between the two helpers:
 
     >>> def pdb_skipped_decorator(function):
     ...
     ...
     ...     def wrapped_fn(*args, **kwargs):
     ...         __debuggerskip__ = True
     ...         helper_1()
     ...         __debuggerskip__ = False
     ...         result = function(*args, **kwargs)
     ...         __debuggerskip__ = True
     ...         helper_2()
     ...         # setting __debuggerskip__ to False again is not necessary
     ...         return result
     ...
     ...     return wrapped_fn
 
 When decorating a function, ipdb will directly step into ``bar()`` by
 default:
 
     >>> @foo_decorator
     ... def bar(x, y):
     ...     return x * y
 
 
 You can toggle the behavior with
 
     ipdb> skip_predicates debuggerskip false
 
 or configure it in your ``.pdbrc``
 
 
 
 License
 -------
 
 Modified from the standard pdb.Pdb class to avoid including readline, so that
 the command line completion of other programs which include this isn't
 damaged.
 
 In the future, this class will be expanded with improvements over the standard
 pdb.
 
 The original code in this file is mainly lifted out of cmd.py in Python 2.2,
 with minor changes. Licensing should therefore be under the standard Python
 terms.  For details on the PSF (Python Software Foundation) standard license,
 see:
 
 https://docs.python.org/2/license.html
 
 
 All the changes since then are under the same license as IPython.
 
 """
 
 #*****************************************************************************
 #
 #       This file is licensed under the PSF license.
 #
 #       Copyright (C) 2001 Python Software Foundation, www.python.org
 #       Copyright (C) 2005-2006 Fernando Perez. <[e-mail]>
 #
 #
 #*****************************************************************************
 
 import inspect
 import linecache
 import sys
 import re
 import os
 
 from IPython import get_ipython
 from contextlib import contextmanager
 from IPython.utils import PyColorize
 from IPython.utils import coloransi, py3compat
 from IPython.core.excolors import exception_colors
 
 # skip module docstests
 __skip_doctest__ = True
 
 prompt = 'ipdb> '
 
 # We have to check this directly from sys.argv, config struct not yet available
 from pdb import Pdb as OldPdb
 
 # Allow the set_trace code to operate outside of an ipython instance, even if
 # it does so with some limitations.  The rest of this support is implemented in
 # the Tracer constructor.
 
 DEBUGGERSKIP = "__debuggerskip__"
 
 
 # this has been implemented in Pdb in Python 3.13 (https://github.com/python/cpython/pull/106676
 # on lower python versions, we backported the feature.
 CHAIN_EXCEPTIONS = sys.version_info < (3, 13)
 
 
 def make_arrow(pad):
     """generate the leading arrow in front of traceback or debugger"""
     if pad >= 2:
         return '-'*(pad-2) + '> '
     elif pad == 1:
         return '>'
     return ''
 
 
 def BdbQuit_excepthook(et, ev, tb, excepthook=None):
     """Exception hook which handles `BdbQuit` exceptions.
 
     All other exceptions are processed using the `excepthook`
     parameter.
     """
     raise ValueError(
         "`BdbQuit_excepthook` is deprecated since version 5.1",
     )
 
 
 def BdbQuit_IPython_excepthook(self, et, ev, tb, tb_offset=None):
     raise ValueError(
         "`BdbQuit_IPython_excepthook` is deprecated since version 5.1",
         DeprecationWarning, stacklevel=2)
 
 
 RGX_EXTRA_INDENT = re.compile(r'(?<=\n)\s+')
 
 
 def strip_indentation(multiline_string):
     return RGX_EXTRA_INDENT.sub('', multiline_string)
 
 
 def decorate_fn_with_doc(new_fn, old_fn, additional_text=""):
     """Make new_fn have old_fn's doc string. This is particularly useful
     for the ``do_...`` commands that hook into the help system.
     Adapted from from a comp.lang.python posting
     by Duncan Booth."""
     def wrapper(*args, **kw):
         return new_fn(*args, **kw)
     if old_fn.__doc__:
         wrapper.__doc__ = strip_indentation(old_fn.__doc__) + additional_text
     return wrapper
 
 
 class Pdb(OldPdb):
     """Modified Pdb class, does not load readline.
 
     for a standalone version that uses prompt_toolkit, see
     `IPython.terminal.debugger.TerminalPdb` and
     `IPython.terminal.debugger.set_trace()`
 
 
     This debugger can hide and skip frames that are tagged according to some predicates.
     See the `skip_predicates` commands.
 
     """
 
     if CHAIN_EXCEPTIONS:
         MAX_CHAINED_EXCEPTION_DEPTH = 999
 
     default_predicates = {
         "tbhide": True,
         "readonly": False,
         "ipython_internal": True,
         "debuggerskip": True,
     }
 
     def __init__(self, completekey=None, stdin=None, stdout=None, context=5, **kwargs):
         """Create a new IPython debugger.
 
         Parameters
         ----------
         completekey : default None
             Passed to pdb.Pdb.
         stdin : default None
             Passed to pdb.Pdb.
         stdout : default None
             Passed to pdb.Pdb.
         context : int
             Number of lines of source code context to show when
             displaying stacktrace information.
         **kwargs
             Passed to pdb.Pdb.
 
         Notes
         -----
         The possibilities are python version dependent, see the python
         docs for more info.
         """
 
         # Parent constructor:
         try:
             self.context = int(context)
             if self.context <= 0:
                 raise ValueError("Context must be a positive integer")
         except (TypeError, ValueError) as e:
                 raise ValueError("Context must be a positive integer") from e
 
         # `kwargs` ensures full compatibility with stdlib's `pdb.Pdb`.
         OldPdb.__init__(self, completekey, stdin, stdout, **kwargs)
 
         # IPython changes...
         self.shell = get_ipython()
 
         if self.shell is None:
             save_main = sys.modules['__main__']
             # No IPython instance running, we must create one
             from IPython.terminal.interactiveshell import \
                 TerminalInteractiveShell
             self.shell = TerminalInteractiveShell.instance()
             # needed by any code which calls __import__("__main__") after
             # the debugger was entered. See also #9941.
             sys.modules["__main__"] = save_main
 
 
         color_scheme = self.shell.colors
 
         self.aliases = {}
 
         # Create color table: we copy the default one from the traceback
         # module and add a few attributes needed for debugging
         self.color_scheme_table = exception_colors()
 
         # shorthands
         C = coloransi.TermColors
         cst = self.color_scheme_table
 
         cst['NoColor'].colors.prompt = C.NoColor
         cst['NoColor'].colors.breakpoint_enabled = C.NoColor
         cst['NoColor'].colors.breakpoint_disabled = C.NoColor
 
         cst['Linux'].colors.prompt = C.Green
         cst['Linux'].colors.breakpoint_enabled = C.LightRed
         cst['Linux'].colors.breakpoint_disabled = C.Red
 
         cst['LightBG'].colors.prompt = C.Blue
         cst['LightBG'].colors.breakpoint_enabled = C.LightRed
         cst['LightBG'].colors.breakpoint_disabled = C.Red
 
         cst['Neutral'].colors.prompt = C.Blue
         cst['Neutral'].colors.breakpoint_enabled = C.LightRed
         cst['Neutral'].colors.breakpoint_disabled = C.Red
 
         # Add a python parser so we can syntax highlight source while
         # debugging.
         self.parser = PyColorize.Parser(style=color_scheme)
         self.set_colors(color_scheme)
 
         # Set the prompt - the default prompt is '(Pdb)'
         self.prompt = prompt
         self.skip_hidden = True
         self.report_skipped = True
 
         # list of predicates we use to skip frames
         self._predicates = self.default_predicates
 
         if CHAIN_EXCEPTIONS:
             self._chained_exceptions = tuple()
             self._chained_exception_index = 0
 
     #
     def set_colors(self, scheme):
         """Shorthand access to the color table scheme selector method."""
         self.color_scheme_table.set_active_scheme(scheme)
         self.parser.style = scheme
 
     def set_trace(self, frame=None):
         if frame is None:
             frame = sys._getframe().f_back
         self.initial_frame = frame
         return super().set_trace(frame)
 
     def _hidden_predicate(self, frame):
         """
         Given a frame return whether it it should be hidden or not by IPython.
         """
 
         if self._predicates["readonly"]:
             fname = frame.f_code.co_filename
             # we need to check for file existence and interactively define
             # function would otherwise appear as RO.
             if os.path.isfile(fname) and not os.access(fname, os.W_OK):
                 return True
 
         if self._predicates["tbhide"]:
             if frame in (self.curframe, getattr(self, "initial_frame", None)):
                 return False
             frame_locals = self._get_frame_locals(frame)
             if "__tracebackhide__" not in frame_locals:
                 return False
             return frame_locals["__tracebackhide__"]
         return False
 
     def hidden_frames(self, stack):
         """
         Given an index in the stack return whether it should be skipped.
 
         This is used in up/down and where to skip frames.
         """
         # The f_locals dictionary is updated from the actual frame
         # locals whenever the .f_locals accessor is called, so we
         # avoid calling it here to preserve self.curframe_locals.
         # Furthermore, there is no good reason to hide the current frame.
         ip_hide = [self._hidden_predicate(s[0]) for s in stack]
         ip_start = [i for i, s in enumerate(ip_hide) if s == "__ipython_bottom__"]
         if ip_start and self._predicates["ipython_internal"]:
             ip_hide = [h if i > ip_start[0] else True for (i, h) in enumerate(ip_hide)]
         return ip_hide
 
     if CHAIN_EXCEPTIONS:
 
         def _get_tb_and_exceptions(self, tb_or_exc):
             """
             Given a tracecack or an exception, return a tuple of chained exceptions
             and current traceback to inspect.
             This will deal with selecting the right ``__cause__`` or ``__context__``
             as well as handling cycles, and return a flattened list of exceptions we
             can jump to with do_exceptions.
             """
             _exceptions = []
             if isinstance(tb_or_exc, BaseException):
                 traceback, current = tb_or_exc.__traceback__, tb_or_exc
 
                 while current is not None:
                     if current in _exceptions:
                         break
                     _exceptions.append(current)
                     if current.__cause__ is not None:
                         current = current.__cause__
                     elif (
                         current.__context__ is not None
                         and not current.__suppress_context__
                     ):
                         current = current.__context__
 
                     if len(_exceptions) >= self.MAX_CHAINED_EXCEPTION_DEPTH:
                         self.message(
                             f"More than {self.MAX_CHAINED_EXCEPTION_DEPTH}"
                             " chained exceptions found, not all exceptions"
                             "will be browsable with `exceptions`."
                         )
                         break
             else:
                 traceback = tb_or_exc
             return tuple(reversed(_exceptions)), traceback
 
         @contextmanager
         def _hold_exceptions(self, exceptions):
             """
             Context manager to ensure proper cleaning of exceptions references
             When given a chained exception instead of a traceback,
             pdb may hold references to many objects which may leak memory.
             We use this context manager to make sure everything is properly cleaned
             """
             try:
                 self._chained_exceptions = exceptions
                 self._chained_exception_index = len(exceptions) - 1
                 yield
             finally:
                 # we can't put those in forget as otherwise they would
                 # be cleared on exception change
                 self._chained_exceptions = tuple()
                 self._chained_exception_index = 0
 
         def do_exceptions(self, arg):
             """exceptions [number]
             List or change current exception in an exception chain.
             Without arguments, list all the current exception in the exception
             chain. Exceptions will be numbered, with the current exception indicated
             with an arrow.
             If given an integer as argument, switch to the exception at that index.
             """
             if not self._chained_exceptions:
                 self.message(
                     "Did not find chained exceptions. To move between"
                     " exceptions, pdb/post_mortem must be given an exception"
                     " object rather than a traceback."
                 )
                 return
             if not arg:
                 for ix, exc in enumerate(self._chained_exceptions):
                     prompt = ">" if ix == self._chained_exception_index else " "
                     rep = repr(exc)
                     if len(rep) > 80:
                         rep = rep[:77] + "..."
                     indicator = (
                         "  -"
                         if self._chained_exceptions[ix].__traceback__ is None
                         else f"{ix:>3}"
                     )
                     self.message(f"{prompt} {indicator} {rep}")
             else:
                 try:
                     number = int(arg)
                 except ValueError:
                     self.error("Argument must be an integer")
                     return
                 if 0 <= number < len(self._chained_exceptions):
                     if self._chained_exceptions[number].__traceback__ is None:
                         self.error(
                             "This exception does not have a traceback, cannot jump to it"
                         )
                         return
 
                     self._chained_exception_index = number
                     self.setup(None, self._chained_exceptions[number].__traceback__)
                     self.print_stack_entry(self.stack[self.curindex])
                 else:
                     self.error("No exception with that number")
 
     def interaction(self, frame, tb_or_exc):
         try:
             if CHAIN_EXCEPTIONS:
                 # this context manager is part of interaction in 3.13
                 _chained_exceptions, tb = self._get_tb_and_exceptions(tb_or_exc)
                 if isinstance(tb_or_exc, BaseException):
                     assert tb is not None, "main exception must have a traceback"
                 with self._hold_exceptions(_chained_exceptions):
                     OldPdb.interaction(self, frame, tb)
             else:
                 OldPdb.interaction(self, frame, tb_or_exc)
 
         except KeyboardInterrupt:
             self.stdout.write("\n" + self.shell.get_exception_only())
 
     def precmd(self, line):
         """Perform useful escapes on the command before it is executed."""
 
         if line.endswith("??"):
             line = "pinfo2 " + line[:-2]
         elif line.endswith("?"):
             line = "pinfo " + line[:-1]
 
         line = super().precmd(line)
 
         return line
 
     def new_do_frame(self, arg):
         OldPdb.do_frame(self, arg)
 
     def new_do_quit(self, arg):
 
         if hasattr(self, 'old_all_completions'):
             self.shell.Completer.all_completions = self.old_all_completions
 
         return OldPdb.do_quit(self, arg)
 
     do_q = do_quit = decorate_fn_with_doc(new_do_quit, OldPdb.do_quit)
 
     def new_do_restart(self, arg):
         """Restart command. In the context of ipython this is exactly the same
         thing as 'quit'."""
         self.msg("Restart doesn't make sense here. Using 'quit' instead.")
         return self.do_quit(arg)
 
     def print_stack_trace(self, context=None):
         Colors = self.color_scheme_table.active_colors
         ColorsNormal = Colors.Normal
         if context is None:
             context = self.context
         try:
             context = int(context)
             if context <= 0:
                 raise ValueError("Context must be a positive integer")
         except (TypeError, ValueError) as e:
                 raise ValueError("Context must be a positive integer") from e
         try:
             skipped = 0
             for hidden, frame_lineno in zip(self.hidden_frames(self.stack), self.stack):
                 if hidden and self.skip_hidden:
                     skipped += 1
                     continue
                 if skipped:
                     print(
                         f"{Colors.excName}    [... skipping {skipped} hidden frame(s)]{ColorsNormal}\n"
                     )
                     skipped = 0
                 self.print_stack_entry(frame_lineno, context=context)
             if skipped:
                 print(
                     f"{Colors.excName}    [... skipping {skipped} hidden frame(s)]{ColorsNormal}\n"
                 )
         except KeyboardInterrupt:
             pass
 
     def print_stack_entry(self, frame_lineno, prompt_prefix='\n-> ',
                           context=None):
         if context is None:
             context = self.context
         try:
             context = int(context)
             if context <= 0:
                 raise ValueError("Context must be a positive integer")
         except (TypeError, ValueError) as e:
                 raise ValueError("Context must be a positive integer") from e
         print(self.format_stack_entry(frame_lineno, '', context), file=self.stdout)
 
         # vds: >>
         frame, lineno = frame_lineno
         filename = frame.f_code.co_filename
         self.shell.hooks.synchronize_with_editor(filename, lineno, 0)
         # vds: <<
 
     def _get_frame_locals(self, frame):
         """ "
         Accessing f_local of current frame reset the namespace, so we want to avoid
         that or the following can happen
 
         ipdb> foo
         "old"
         ipdb> foo = "new"
         ipdb> foo
         "new"
         ipdb> where
         ipdb> foo
         "old"
 
         So if frame is self.current_frame we instead return self.curframe_locals
 
         """
         if frame is self.curframe:
             return self.curframe_locals
         else:
             return frame.f_locals
 
     def format_stack_entry(self, frame_lineno, lprefix=': ', context=None):
         if context is None:
             context = self.context
         try:
             context = int(context)
             if context <= 0:
                 print("Context must be a positive integer", file=self.stdout)
         except (TypeError, ValueError):
                 print("Context must be a positive integer", file=self.stdout)
 
         import reprlib
 
         ret = []
 
         Colors = self.color_scheme_table.active_colors
         ColorsNormal = Colors.Normal
         tpl_link = "%s%%s%s" % (Colors.filenameEm, ColorsNormal)
         tpl_call = "%s%%s%s%%s%s" % (Colors.vName, Colors.valEm, ColorsNormal)
         tpl_line = "%%s%s%%s %s%%s" % (Colors.lineno, ColorsNormal)
         tpl_line_em = "%%s%s%%s %s%%s%s" % (Colors.linenoEm, Colors.line, ColorsNormal)
 
         frame, lineno = frame_lineno
 
         return_value = ''
         loc_frame = self._get_frame_locals(frame)
         if "__return__" in loc_frame:
             rv = loc_frame["__return__"]
             # return_value += '->'
             return_value += reprlib.repr(rv) + "\n"
         ret.append(return_value)
 
         #s = filename + '(' + `lineno` + ')'
         filename = self.canonic(frame.f_code.co_filename)
         link = tpl_link % py3compat.cast_unicode(filename)
 
         if frame.f_code.co_name:
             func = frame.f_code.co_name
         else:
             func = "<lambda>"
 
         call = ""
         if func != "?":
             if "__args__" in loc_frame:
                 args = reprlib.repr(loc_frame["__args__"])
             else:
                 args = '()'
             call = tpl_call % (func, args)
 
         # The level info should be generated in the same format pdb uses, to
         # avoid breaking the pdbtrack functionality of python-mode in *emacs.
         if frame is self.curframe:
             ret.append('> ')
         else:
             ret.append("  ")
         ret.append("%s(%s)%s\n" % (link, lineno, call))
 
         start = lineno - 1 - context//2
         lines = linecache.getlines(filename)
         start = min(start, len(lines) - context)
         start = max(start, 0)
         lines = lines[start : start + context]
 
         for i, line in enumerate(lines):
             show_arrow = start + 1 + i == lineno
             linetpl = (frame is self.curframe or show_arrow) and tpl_line_em or tpl_line
             ret.append(
                 self.__format_line(
                     linetpl, filename, start + 1 + i, line, arrow=show_arrow
                 )
             )
         return "".join(ret)
 
     def __format_line(self, tpl_line, filename, lineno, line, arrow=False):
         bp_mark = ""
         bp_mark_color = ""
 
         new_line, err = self.parser.format2(line, 'str')
         if not err:
             line = new_line
 
         bp = None
         if lineno in self.get_file_breaks(filename):
             bps = self.get_breaks(filename, lineno)
             bp = bps[-1]
 
         if bp:
             Colors = self.color_scheme_table.active_colors
             bp_mark = str(bp.number)
             bp_mark_color = Colors.breakpoint_enabled
             if not bp.enabled:
                 bp_mark_color = Colors.breakpoint_disabled
 
         numbers_width = 7
         if arrow:
             # This is the line with the error
             pad = numbers_width - len(str(lineno)) - len(bp_mark)
             num = '%s%s' % (make_arrow(pad), str(lineno))
         else:
             num = '%*s' % (numbers_width - len(bp_mark), str(lineno))
 
         return tpl_line % (bp_mark_color + bp_mark, num, line)
 
     def print_list_lines(self, filename, first, last):
         """The printing (as opposed to the parsing part of a 'list'
         command."""
         try:
             Colors = self.color_scheme_table.active_colors
             ColorsNormal = Colors.Normal
             tpl_line = '%%s%s%%s %s%%s' % (Colors.lineno, ColorsNormal)
             tpl_line_em = '%%s%s%%s %s%%s%s' % (Colors.linenoEm, Colors.line, ColorsNormal)
             src = []
             if filename == "<string>" and hasattr(self, "_exec_filename"):
                 filename = self._exec_filename
 
             for lineno in range(first, last+1):
                 line = linecache.getline(filename, lineno)
                 if not line:
                     break
 
                 if lineno == self.curframe.f_lineno:
                     line = self.__format_line(
                         tpl_line_em, filename, lineno, line, arrow=True
                     )
                 else:
                     line = self.__format_line(
                         tpl_line, filename, lineno, line, arrow=False
                     )
 
                 src.append(line)
                 self.lineno = lineno
 
             print(''.join(src), file=self.stdout)
 
         except KeyboardInterrupt:
             pass
 
     def do_skip_predicates(self, args):
         """
         Turn on/off individual predicates as to whether a frame should be hidden/skip.
 
         The global option to skip (or not) hidden frames is set with skip_hidden
 
         To change the value of a predicate
 
             skip_predicates key [true|false]
 
         Call without arguments to see the current values.
 
         To permanently change the value of an option add the corresponding
         command to your ``~/.pdbrc`` file. If you are programmatically using the
         Pdb instance you can also change the ``default_predicates`` class
         attribute.
         """
         if not args.strip():
             print("current predicates:")
             for p, v in self._predicates.items():
                 print("   ", p, ":", v)
             return
         type_value = args.strip().split(" ")
         if len(type_value) != 2:
             print(
                 f"Usage: skip_predicates <type> <value>, with <type> one of {set(self._predicates.keys())}"
             )
             return
 
         type_, value = type_value
         if type_ not in self._predicates:
             print(f"{type_!r} not in {set(self._predicates.keys())}")
             return
         if value.lower() not in ("true", "yes", "1", "no", "false", "0"):
             print(
                 f"{value!r} is invalid - use one of ('true', 'yes', '1', 'no', 'false', '0')"
             )
             return
 
         self._predicates[type_] = value.lower() in ("true", "yes", "1")
         if not any(self._predicates.values()):
             print(
                 "Warning, all predicates set to False, skip_hidden may not have any effects."
             )
 
     def do_skip_hidden(self, arg):
         """
         Change whether or not we should skip frames with the
         __tracebackhide__ attribute.
         """
         if not arg.strip():
             print(
                 f"skip_hidden = {self.skip_hidden}, use 'yes','no', 'true', or 'false' to change."
             )
         elif arg.strip().lower() in ("true", "yes"):
             self.skip_hidden = True
         elif arg.strip().lower() in ("false", "no"):
             self.skip_hidden = False
         if not any(self._predicates.values()):
             print(
                 "Warning, all predicates set to False, skip_hidden may not have any effects."
             )
 
     def do_list(self, arg):
         """Print lines of code from the current stack frame
         """
         self.lastcmd = 'list'
         last = None
         if arg and arg != ".":
             try:
                 x = eval(arg, {}, {})
                 if type(x) == type(()):
                     first, last = x
                     first = int(first)
                     last = int(last)
                     if last < first:
                         # Assume it's a count
                         last = first + last
                 else:
                     first = max(1, int(x) - 5)
             except:
                 print('*** Error in argument:', repr(arg), file=self.stdout)
                 return
         elif self.lineno is None or arg == ".":
             first = max(1, self.curframe.f_lineno - 5)
         else:
             first = self.lineno + 1
         if last is None:
             last = first + 10
         self.print_list_lines(self.curframe.f_code.co_filename, first, last)
 
         # vds: >>
         lineno = first
         filename = self.curframe.f_code.co_filename
         self.shell.hooks.synchronize_with_editor(filename, lineno, 0)
         # vds: <<
 
     do_l = do_list
 
     def getsourcelines(self, obj):
         lines, lineno = inspect.findsource(obj)
         if inspect.isframe(obj) and obj.f_globals is self._get_frame_locals(obj):
             # must be a module frame: do not try to cut a block out of it
             return lines, 1
         elif inspect.ismodule(obj):
             return lines, 1
         return inspect.getblock(lines[lineno:]), lineno+1
 
     def do_longlist(self, arg):
         """Print lines of code from the current stack frame.
 
         Shows more lines than 'list' does.
         """
         self.lastcmd = 'longlist'
         try:
             lines, lineno = self.getsourcelines(self.curframe)
         except OSError as err:
             self.error(err)
             return
         last = lineno + len(lines)
         self.print_list_lines(self.curframe.f_code.co_filename, lineno, last)
     do_ll = do_longlist
 
     def do_debug(self, arg):
         """debug code
         Enter a recursive debugger that steps through the code
         argument (which is an arbitrary expression or statement to be
         executed in the current environment).
         """
         trace_function = sys.gettrace()
         sys.settrace(None)
         globals = self.curframe.f_globals
         locals = self.curframe_locals
         p = self.__class__(completekey=self.completekey,
                            stdin=self.stdin, stdout=self.stdout)
         p.use_rawinput = self.use_rawinput
         p.prompt = "(%s) " % self.prompt.strip()
         self.message("ENTERING RECURSIVE DEBUGGER")
         sys.call_tracing(p.run, (arg, globals, locals))
         self.message("LEAVING RECURSIVE DEBUGGER")
         sys.settrace(trace_function)
         self.lastcmd = p.lastcmd
 
     def do_pdef(self, arg):
         """Print the call signature for any callable object.
 
         The debugger interface to %pdef"""
         namespaces = [
             ("Locals", self.curframe_locals),
             ("Globals", self.curframe.f_globals),
         ]
         self.shell.find_line_magic("pdef")(arg, namespaces=namespaces)
 
     def do_pdoc(self, arg):
         """Print the docstring for an object.
 
         The debugger interface to %pdoc."""
         namespaces = [
             ("Locals", self.curframe_locals),
             ("Globals", self.curframe.f_globals),
         ]
         self.shell.find_line_magic("pdoc")(arg, namespaces=namespaces)
 
     def do_pfile(self, arg):
         """Print (or run through pager) the file where an object is defined.
 
         The debugger interface to %pfile.
         """
         namespaces = [
             ("Locals", self.curframe_locals),
             ("Globals", self.curframe.f_globals),
         ]
         self.shell.find_line_magic("pfile")(arg, namespaces=namespaces)
 
     def do_pinfo(self, arg):
         """Provide detailed information about an object.
 
         The debugger interface to %pinfo, i.e., obj?."""
         namespaces = [
             ("Locals", self.curframe_locals),
             ("Globals", self.curframe.f_globals),
         ]
         self.shell.find_line_magic("pinfo")(arg, namespaces=namespaces)
 
     def do_pinfo2(self, arg):
         """Provide extra detailed information about an object.
 
         The debugger interface to %pinfo2, i.e., obj??."""
         namespaces = [
             ("Locals", self.curframe_locals),
             ("Globals", self.curframe.f_globals),
         ]
         self.shell.find_line_magic("pinfo2")(arg, namespaces=namespaces)
 
     def do_psource(self, arg):
         """Print (or run through pager) the source code for an object."""
         namespaces = [
             ("Locals", self.curframe_locals),
             ("Globals", self.curframe.f_globals),
         ]
         self.shell.find_line_magic("psource")(arg, namespaces=namespaces)
 
     def do_where(self, arg):
         """w(here)
         Print a stack trace, with the most recent frame at the bottom.
         An arrow indicates the "current frame", which determines the
         context of most commands. 'bt' is an alias for this command.
 
         Take a number as argument as an (optional) number of context line to
         print"""
         if arg:
             try:
                 context = int(arg)
             except ValueError as err:
                 self.error(err)
                 return
             self.print_stack_trace(context)
         else:
             self.print_stack_trace()
 
     do_w = do_where
 
     def break_anywhere(self, frame):
         """
         _stop_in_decorator_internals is overly restrictive, as we may still want
         to trace function calls, so we need to also update break_anywhere so
         that is we don't `stop_here`, because of debugger skip, we may still
         stop at any point inside the function
 
         """
 
         sup = super().break_anywhere(frame)
         if sup:
             return sup
         if self._predicates["debuggerskip"]:
             if DEBUGGERSKIP in frame.f_code.co_varnames:
                 return True
             if frame.f_back and self._get_frame_locals(frame.f_back).get(DEBUGGERSKIP):
                 return True
         return False
 
     def _is_in_decorator_internal_and_should_skip(self, frame):
         """
         Utility to tell us whether we are in a decorator internal and should stop.
 
         """
 
         # if we are disabled don't skip
         if not self._predicates["debuggerskip"]:
             return False
 
         # if frame is tagged, skip by default.
         if DEBUGGERSKIP in frame.f_code.co_varnames:
             return True
 
         # if one of the parent frame value set to True skip as well.
 
         cframe = frame
         while getattr(cframe, "f_back", None):
             cframe = cframe.f_back
             if self._get_frame_locals(cframe).get(DEBUGGERSKIP):
                 return True
 
         return False
 
     def stop_here(self, frame):
         if self._is_in_decorator_internal_and_should_skip(frame) is True:
             return False
 
         hidden = False
         if self.skip_hidden:
             hidden = self._hidden_predicate(frame)
         if hidden:
             if self.report_skipped:
                 Colors = self.color_scheme_table.active_colors
                 ColorsNormal = Colors.Normal
                 print(
                     f"{Colors.excName}    [... skipped 1 hidden frame]{ColorsNormal}\n"
                 )
         return super().stop_here(frame)
 
     def do_up(self, arg):
         """u(p) [count]
         Move the current frame count (default one) levels up in the
         stack trace (to an older frame).
 
         Will skip hidden frames.
         """
         # modified version of upstream that skips
         # frames with __tracebackhide__
         if self.curindex == 0:
             self.error("Oldest frame")
             return
         try:
             count = int(arg or 1)
         except ValueError:
             self.error("Invalid frame count (%s)" % arg)
             return
         skipped = 0
         if count < 0:
             _newframe = 0
         else:
             counter = 0
             hidden_frames = self.hidden_frames(self.stack)
             for i in range(self.curindex - 1, -1, -1):
                 if hidden_frames[i] and self.skip_hidden:
                     skipped += 1
                     continue
                 counter += 1
                 if counter >= count:
                     break
             else:
                 # if no break occurred.
                 self.error(
                     "all frames above hidden, use `skip_hidden False` to get get into those."
                 )
                 return
 
             Colors = self.color_scheme_table.active_colors
             ColorsNormal = Colors.Normal
             _newframe = i
         self._select_frame(_newframe)
         if skipped:
             print(
                 f"{Colors.excName}    [... skipped {skipped} hidden frame(s)]{ColorsNormal}\n"
             )
 
     def do_down(self, arg):
         """d(own) [count]
         Move the current frame count (default one) levels down in the
         stack trace (to a newer frame).
 
         Will skip hidden frames.
         """
         if self.curindex + 1 == len(self.stack):
             self.error("Newest frame")
             return
         try:
             count = int(arg or 1)
         except ValueError:
             self.error("Invalid frame count (%s)" % arg)
             return
         if count < 0:
             _newframe = len(self.stack) - 1
         else:
             counter = 0
             skipped = 0
             hidden_frames = self.hidden_frames(self.stack)
             for i in range(self.curindex + 1, len(self.stack)):
                 if hidden_frames[i] and self.skip_hidden:
                     skipped += 1
                     continue
                 counter += 1
                 if counter >= count:
                     break
             else:
                 self.error(
                     "all frames below hidden, use `skip_hidden False` to get get into those."
                 )
                 return
 
             Colors = self.color_scheme_table.active_colors
             ColorsNormal = Colors.Normal
             if skipped:
                 print(
                     f"{Colors.excName}    [... skipped {skipped} hidden frame(s)]{ColorsNormal}\n"
                 )
             _newframe = i
 
         self._select_frame(_newframe)
 
     do_d = do_down
     do_u = do_up
 
     def do_context(self, context):
         """context number_of_lines
         Set the number of lines of source code to show when displaying
         stacktrace information.
         """
         try:
             new_context = int(context)
             if new_context <= 0:
                 raise ValueError()
             self.context = new_context
         except ValueError:
             self.error("The 'context' command requires a positive integer argument.")
 
 
 class InterruptiblePdb(Pdb):
     """Version of debugger where KeyboardInterrupt exits the debugger altogether."""
 
     def cmdloop(self, intro=None):
         """Wrap cmdloop() such that KeyboardInterrupt stops the debugger."""
         try:
             return OldPdb.cmdloop(self, intro=intro)
         except KeyboardInterrupt:
             self.stop_here = lambda frame: False
             self.do_quit("")
             sys.settrace(None)
             self.quitting = False
             raise
 
     def _cmdloop(self):
         while True:
             try:
                 # keyboard interrupts allow for an easy way to cancel
                 # the current command, so allow them during interactive input
                 self.allow_kbdint = True
                 self.cmdloop()
                 self.allow_kbdint = False
                 break
             except KeyboardInterrupt:
                 self.message('--KeyboardInterrupt--')
                 raise
 
 
-def set_trace(frame=None):
+def set_trace(frame=None, header=None):
     """
     Start debugging from `frame`.
 
     If frame is not specified, debugging starts from caller's frame.
     """
-    Pdb().set_trace(frame or sys._getframe().f_back)
+    pdb = Pdb()
+    if header is not None:
+        pdb.message(header)
+    pdb.set_trace(frame or sys._getframe().f_back)