cpython/Lib/pdb.py at 3.14 · python/cpython · GitHub

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"""
The Python Debugger Pdb
=======================

To use the debugger in its simplest form:

        >>> import pdb
        >>> pdb.run('<a statement>')

The debugger's prompt is '(Pdb) '.  This will stop in the first
function call in <a statement>.

Alternatively, if a statement terminated with an unhandled exception,
you can use pdb's post-mortem facility to inspect the contents of the
traceback:

        >>> <a statement>
        <exception traceback>
        >>> import pdb
        >>> pdb.pm()

The commands recognized by the debugger are listed in the next
section.  Most can be abbreviated as indicated; e.g., h(elp) means
that 'help' can be typed as 'h' or 'help' (but not as 'he' or 'hel',
nor as 'H' or 'Help' or 'HELP').  Optional arguments are enclosed in
square brackets.  Alternatives in the command syntax are separated
by a vertical bar (|).

A blank line repeats the previous command literally, except for
'list', where it lists the next 11 lines.

Commands that the debugger doesn't recognize are assumed to be Python
statements and are executed in the context of the program being
debugged.  Python statements can also be prefixed with an exclamation
point ('!').  This is a powerful way to inspect the program being
debugged; it is even possible to change variables or call functions.
When an exception occurs in such a statement, the exception name is
printed but the debugger's state is not changed.

The debugger supports aliases, which can save typing.  And aliases can
have parameters (see the alias help entry) which allows one a certain
level of adaptability to the context under examination.

Multiple commands may be entered on a single line, separated by the
pair ';;'.  No intelligence is applied to separating the commands; the
input is split at the first ';;', even if it is in the middle of a
quoted string.

If a file ".pdbrc" exists in your home directory or in the current
directory, it is read in and executed as if it had been typed at the
debugger prompt.  This is particularly useful for aliases.  If both
files exist, the one in the home directory is read first and aliases
defined there can be overridden by the local file.  This behavior can be
disabled by passing the "readrc=False" argument to the Pdb constructor.

Aside from aliases, the debugger is not directly programmable; but it
is implemented as a class from which you can derive your own debugger
class, which you can make as fancy as you like.


Debugger commands
=================

"""
# NOTE: the actual command documentation is collected from docstrings of the
# commands and is appended to __doc__ after the class has been defined.

import os
import io
import re
import sys
import cmd
import bdb
import dis
import code
import glob
import json
import stat
import token
import types
import atexit
import codeop
import pprint
import signal
import socket
import typing
import asyncio
import inspect
import weakref
import builtins
import tempfile
import textwrap
import tokenize
import itertools
import traceback
import linecache
import selectors
import threading
import _colorize
import _pyrepl.utils

from contextlib import ExitStack, closing, contextmanager
from types import CodeType
from warnings import deprecated


class Restart(Exception):
    """Causes a debugger to be restarted for the debugged python program."""
    pass

__all__ = ["run", "pm", "Pdb", "runeval", "runctx", "runcall", "set_trace",
           "post_mortem", "set_default_backend", "get_default_backend", "help"]


def find_first_executable_line(code):
    """ Try to find the first executable line of the code object.

    Equivalently, find the line number of the instruction that's
    after RESUME

    Return code.co_firstlineno if no executable line is found.
    """
    prev = None
    for instr in dis.get_instructions(code):
        if prev is not None and prev.opname == 'RESUME':
            if instr.positions.lineno is not None:
                return instr.positions.lineno
            return code.co_firstlineno
        prev = instr
    return code.co_firstlineno

def find_function(funcname, filename):
    cre = re.compile(r'def\s+%s(\s*\[.+\])?\s*[(]' % re.escape(funcname))
    try:
        fp = tokenize.open(filename)
    except OSError:
        lines = linecache.getlines(filename)
        if not lines:
            return None
        fp = io.StringIO(''.join(lines))
    funcdef = ""
    funcstart = 0
    # consumer of this info expects the first line to be 1
    with fp:
        for lineno, line in enumerate(fp, start=1):
            if cre.match(line):
                funcstart, funcdef = lineno, line
            elif funcdef:
                funcdef += line

            if funcdef:
                try:
                    code = compile(funcdef, filename, 'exec')
                except SyntaxError:
                    continue
                # We should always be able to find the code object here
                funccode = next(c for c in code.co_consts if
                                isinstance(c, CodeType) and c.co_name == funcname)
                lineno_offset = find_first_executable_line(funccode)
                return funcname, filename, funcstart + lineno_offset - 1
    return None

def lasti2lineno(code, lasti):
    linestarts = list(dis.findlinestarts(code))
    linestarts.reverse()
    for i, lineno in linestarts:
        if lasti >= i:
            return lineno
    return 0


class _rstr(str):
    """String that doesn't quote its repr."""
    def __repr__(self):
        return self


class _ExecutableTarget:
    filename: str
    code: CodeType | str
    namespace: dict


class _ScriptTarget(_ExecutableTarget):
    def __init__(self, target):
        self._check(target)
        self._target = self._safe_realpath(target)

        # If PYTHONSAFEPATH (-P) is not set, sys.path[0] is the directory
        # of pdb, and we should replace it with the directory of the script
        if not sys.flags.safe_path:
            sys.path[0] = os.path.dirname(self._target)

    @staticmethod
    def _check(target):
        """
        Check that target is plausibly a script.
        """
        if not os.path.exists(target):
            print(f'Error: {target} does not exist')
            sys.exit(1)
        if os.path.isdir(target):
            print(f'Error: {target} is a directory')
            sys.exit(1)

    @staticmethod
    def _safe_realpath(path):
        """
        Return the canonical path (realpath) if it is accessible from the userspace.
        Otherwise (for example, if the path is a symlink to an anonymous pipe),
        return the original path.

        See GH-142315.
        """
        realpath = os.path.realpath(path)
        return realpath if os.path.exists(realpath) else path

    def __repr__(self):
        return self._target

    @property
    def filename(self):
        return self._target

    @property
    def code(self):
        # Open the file each time because the file may be modified
        with io.open_code(self._target) as fp:
            return f"exec(compile({fp.read()!r}, {self._target!r}, 'exec'))"

    @property
    def namespace(self):
        return dict(
            __name__='__main__',
            __file__=self._target,
            __builtins__=__builtins__,
            __spec__=None,
        )


class _ModuleTarget(_ExecutableTarget):
    def __init__(self, target):
        self._target = target

        import runpy
        try:
            _, self._spec, self._code = runpy._get_module_details(self._target)
        except ImportError as e:
            print(f"ImportError: {e}")
            sys.exit(1)
        except Exception:
            traceback.print_exc()
            sys.exit(1)

    def __repr__(self):
        return self._target

    @property
    def filename(self):
        return self._code.co_filename

    @property
    def code(self):
        return self._code

    @property
    def namespace(self):
        return dict(
            __name__='__main__',
            __file__=os.path.normcase(os.path.abspath(self.filename)),
            __package__=self._spec.parent,
            __loader__=self._spec.loader,
            __spec__=self._spec,
            __builtins__=__builtins__,
        )


class _ZipTarget(_ExecutableTarget):
    def __init__(self, target):
        import runpy

        self._target = os.path.realpath(target)
        sys.path.insert(0, self._target)
        try:
            _, self._spec, self._code = runpy._get_main_module_details()
        except ImportError as e:
            print(f"ImportError: {e}")
            sys.exit(1)
        except Exception:
            traceback.print_exc()
            sys.exit(1)

    def __repr__(self):
        return self._target

    @property
    def filename(self):
        return self._code.co_filename

    @property
    def code(self):
        return self._code

    @property
    def namespace(self):
        return dict(
            __name__='__main__',
            __file__=os.path.normcase(os.path.abspath(self.filename)),
            __package__=self._spec.parent,
            __loader__=self._spec.loader,
            __spec__=self._spec,
            __builtins__=__builtins__,
        )


class _PdbInteractiveConsole(code.InteractiveConsole):
    def __init__(self, ns, message):
        self._message = message
        super().__init__(locals=ns, local_exit=True)

    def write(self, data):
        self._message(data, end='')


# Interaction prompt line will separate file and call info from code
# text using value of line_prefix string.  A newline and arrow may
# be to your liking.  You can set it once pdb is imported using the
# command "pdb.line_prefix = '\n% '".
# line_prefix = ': '    # Use this to get the old situation back
line_prefix = '\n-> '   # Probably a better default


# The default backend to use for Pdb instances if not specified
# Should be either 'settrace' or 'monitoring'
_default_backend = 'settrace'


def set_default_backend(backend):
    """Set the default backend to use for Pdb instances."""
    global _default_backend
    if backend not in ('settrace', 'monitoring'):
        raise ValueError("Invalid backend: %s" % backend)
    _default_backend = backend


def get_default_backend():
    """Get the default backend to use for Pdb instances."""
    return _default_backend


class Pdb(bdb.Bdb, cmd.Cmd):
    _previous_sigint_handler = None

    # Limit the maximum depth of chained exceptions, we should be handling cycles,
    # but in case there are recursions, we stop at 999.
    MAX_CHAINED_EXCEPTION_DEPTH = 999

    _file_mtime_table = {}

    _last_pdb_instance = None

    def __init__(self, completekey='tab', stdin=None, stdout=None, skip=None,
                 nosigint=False, readrc=True, mode=None, backend=None, colorize=False):
        bdb.Bdb.__init__(self, skip=skip, backend=backend if backend else get_default_backend())
        cmd.Cmd.__init__(self, completekey, stdin, stdout)
        sys.audit("pdb.Pdb")
        if stdout:
            self.use_rawinput = 0
        self.prompt = '(Pdb) '
        self.aliases = {}
        self.displaying = {}
        self.mainpyfile = ''
        self._wait_for_mainpyfile = False
        self.tb_lineno = {}
        self.mode = mode
        self.colorize = colorize and _colorize.can_colorize(file=stdout or sys.stdout)
        # Try to load readline if it exists
        try:
            import readline
            # remove some common file name delimiters
            readline.set_completer_delims(' \t\n`@#%^&*()=+[{]}\\|;:\'",<>?')
        except ImportError:
            pass

        self.allow_kbdint = False
        self.nosigint = nosigint
        # Consider these characters as part of the command so when the users type
        # c.a or c['a'], it won't be recognized as a c(ontinue) command
        self.identchars = cmd.Cmd.identchars + '=.[](),"\'+-*/%@&|<>~^'

        # Read ~/.pdbrc and ./.pdbrc
        self.rcLines = []
        if readrc:
            try:
                with open(os.path.expanduser('~/.pdbrc'), encoding='utf-8') as rcFile:
                    self.rcLines.extend(rcFile)
            except OSError:
                pass
            try:
                with open(".pdbrc", encoding='utf-8') as rcFile:
                    self.rcLines.extend(rcFile)
            except OSError:
                pass

        self.commands = {} # associates a command list to breakpoint numbers
        self.commands_defining = False # True while in the process of defining
                                       # a command list
        self.commands_bnum = None # The breakpoint number for which we are
                                  # defining a list

        self.async_shim_frame = None
        self.async_awaitable = None

        self._chained_exceptions = tuple()
        self._chained_exception_index = 0

        self._current_task = None

    def set_trace(self, frame=None, *, commands=None):
        Pdb._last_pdb_instance = self
        if frame is None:
            frame = sys._getframe().f_back

        if commands is not None:
            self.rcLines.extend(commands)

        super().set_trace(frame)

    async def set_trace_async(self, frame=None, *, commands=None):
        if self.async_awaitable is not None:
            # We are already in a set_trace_async call, do not mess with it
            return

        if frame is None:
            frame = sys._getframe().f_back

        # We need set_trace to set up the basics, however, this will call
        # set_stepinstr() will we need to compensate for, because we don't
        # want to trigger on calls
        self.set_trace(frame, commands=commands)
        # Changing the stopframe will disable trace dispatch on calls
        self.stopframe = frame
        # We need to stop tracing because we don't have the privilege to avoid
        # triggering tracing functions as normal, as we are not already in
        # tracing functions
        self.stop_trace()

        self.async_shim_frame = sys._getframe()
        self.async_awaitable = None

        while True:
            self.async_awaitable = None
            # Simulate a trace event
            # This should bring up pdb and make pdb believe it's debugging the
            # caller frame
            self.trace_dispatch(frame, "opcode", None)
            if self.async_awaitable is not None:
                try:
                    if self.breaks:
                        with self.set_enterframe(frame):
                            # set_continue requires enterframe to work
                            self.set_continue()
                        self.start_trace()
                    await self.async_awaitable
                except Exception:
                    self._error_exc()
            else:
                break

        self.async_shim_frame = None

        # start the trace (the actual command is already set by set_* calls)
        if self.returnframe is None and self.stoplineno == -1 and not self.breaks:
            # This means we did a continue without any breakpoints, we should not
            # start the trace
            return

        self.start_trace()

    def sigint_handler(self, signum, frame):
        if self.allow_kbdint:
            raise KeyboardInterrupt
        self.message("\nProgram interrupted. (Use 'cont' to resume).")
        self.set_step()
        self.set_trace(frame)

    def reset(self):
        bdb.Bdb.reset(self)
        self.forget()

    def forget(self):
        self.lineno = None
        self.stack = []
        self.curindex = 0
        if hasattr(self, 'curframe') and self.curframe:
            self.curframe.f_globals.pop('__pdb_convenience_variables', None)
        self.curframe = None
        self.tb_lineno.clear()

    def setup(self, f, tb):
        self.forget()
        self.stack, self.curindex = self.get_stack(f, tb)
        while tb:
            # when setting up post-mortem debugging with a traceback, save all
            # the original line numbers to be displayed along the current line
            # numbers (which can be different, e.g. due to finally clauses)
            lineno = lasti2lineno(tb.tb_frame.f_code, tb.tb_lasti)
            self.tb_lineno[tb.tb_frame] = lineno
            tb = tb.tb_next
        self.curframe = self.stack[self.curindex][0]
        self.set_convenience_variable(self.curframe, '_frame', self.curframe)
        if self._current_task:
            self.set_convenience_variable(self.curframe, '_asynctask', self._current_task)
        self._save_initial_file_mtime(self.curframe)

        if self._chained_exceptions:
            self.set_convenience_variable(
                self.curframe,
                '_exception',
                self._chained_exceptions[self._chained_exception_index],
            )

        if self.rcLines:
            self.cmdqueue = [
                line for line in self.rcLines
                if line.strip() and not line.strip().startswith("#")
            ]
            self.rcLines = []

    @property
    @deprecated("The frame locals reference is no longer cached. Use 'curframe.f_locals' instead.")
    def curframe_locals(self):
        return self.curframe.f_locals

    @curframe_locals.setter
    @deprecated("Setting 'curframe_locals' no longer has any effect. Update the contents of 'curframe.f_locals' instead.")
    def curframe_locals(self, value):
        pass

    # Override Bdb methods

    def user_call(self, frame, argument_list):
        """This method is called when there is the remote possibility
        that we ever need to stop in this function."""
        if self._wait_for_mainpyfile:
            return
        if self.stop_here(frame):
            self.message('--Call--')
            self.interaction(frame, None)

    def user_line(self, frame):
        """This function is called when we stop or break at this line."""
        if self._wait_for_mainpyfile:
            if (self.mainpyfile != self.canonic(frame.f_code.co_filename)):
                return
            self._wait_for_mainpyfile = False
        if self.trace_opcodes:
            # GH-127321
            # We want to avoid stopping at an opcode that does not have
            # an associated line number because pdb does not like it
            if frame.f_lineno is None:
                self.set_stepinstr()
                return
        self.bp_commands(frame)
        self.interaction(frame, None)

    user_opcode = user_line

    def bp_commands(self, frame):
        """Call every command that was set for the current active breakpoint
        (if there is one).

        Returns True if the normal interaction function must be called,
        False otherwise."""
        # self.currentbp is set in bdb in Bdb.break_here if a breakpoint was hit
        if getattr(self, "currentbp", False) and \
               self.currentbp in self.commands:
            currentbp = self.currentbp
            self.currentbp = 0
            for line in self.commands[currentbp]:
                self.cmdqueue.append(line)
            self.cmdqueue.append(f'_pdbcmd_restore_lastcmd {self.lastcmd}')

    def user_return(self, frame, return_value):
        """This function is called when a return trap is set here."""
        if self._wait_for_mainpyfile:
            return
        frame.f_locals['__return__'] = return_value
        self.set_convenience_variable(frame, '_retval', return_value)
        self.message('--Return--')
        self.interaction(frame, None)

    def user_exception(self, frame, exc_info):
        """This function is called if an exception occurs,
        but only if we are to stop at or just below this level."""
        if self._wait_for_mainpyfile:
            return
        exc_type, exc_value, exc_traceback = exc_info
        frame.f_locals['__exception__'] = exc_type, exc_value
        self.set_convenience_variable(frame, '_exception', exc_value)

        # An 'Internal StopIteration' exception is an exception debug event
        # issued by the interpreter when handling a subgenerator run with
        # 'yield from' or a generator controlled by a for loop. No exception has
        # actually occurred in this case. The debugger uses this debug event to
        # stop when the debuggee is returning from such generators.
        prefix = 'Internal ' if (not exc_traceback
                                    and exc_type is StopIteration) else ''
        self.message('%s%s' % (prefix, self._format_exc(exc_value)))
        self.interaction(frame, exc_traceback)

    # General interaction function
    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--')

    def _save_initial_file_mtime(self, frame):
        """save the mtime of the all the files in the frame stack in the file mtime table
        if they haven't been saved yet."""
        while frame:
            filename = frame.f_code.co_filename
            if filename not in self._file_mtime_table:
                try:
                    self._file_mtime_table[filename] = os.path.getmtime(filename)
                except Exception:
                    pass
            frame = frame.f_back

    def _validate_file_mtime(self):
        """Check if the source file of the current frame has been modified.
        If so, give a warning and reset the modify time to current."""
        try:
            filename = self.curframe.f_code.co_filename
            mtime = os.path.getmtime(filename)
        except Exception:
            return
        if (filename in self._file_mtime_table and
            mtime != self._file_mtime_table[filename]):
            self.message(f"*** WARNING: file '{filename}' was edited, "
                         "running stale code until the program is rerun")
            self._file_mtime_table[filename] = mtime

    # Called before loop, handles display expressions
    # Set up convenience variable containers
    def _show_display(self):
        displaying = self.displaying.get(self.curframe)
        if displaying:
            for expr, oldvalue in displaying.items():
                newvalue = self._getval_except(expr)
                # check for identity first; this prevents custom __eq__ to
                # be called at every loop, and also prevents instances whose
                # fields are changed to be displayed
                if newvalue is not oldvalue and newvalue != oldvalue:
                    displaying[expr] = newvalue
                    self.message('display %s: %s  [old: %s]' %
                                 (expr, self._safe_repr(newvalue, expr),
                                  self._safe_repr(oldvalue, expr)))

    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 _get_asyncio_task(self):
        try:
            task = asyncio.current_task()
        except RuntimeError:
            task = None
        return task

    def interaction(self, frame, tb_or_exc):
        # Restore the previous signal handler at the Pdb prompt.
        if Pdb._previous_sigint_handler:
            try:
                signal.signal(signal.SIGINT, Pdb._previous_sigint_handler)
            except ValueError:  # ValueError: signal only works in main thread
                pass
            else:
                Pdb._previous_sigint_handler = None

        self._current_task = self._get_asyncio_task()

        _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):
            self.setup(frame, tb)
            # We should print the stack entry if and only if the user input
            # is expected, and we should print it right before the user input.
            # We achieve this by appending _pdbcmd_print_frame_status to the
            # command queue. If cmdqueue is not exhausted, the user input is
            # not expected and we will not print the stack entry.
            self.cmdqueue.append('_pdbcmd_print_frame_status')
            self._cmdloop()
            # If _pdbcmd_print_frame_status is not used, pop it out
            if self.cmdqueue and self.cmdqueue[-1] == '_pdbcmd_print_frame_status':
                self.cmdqueue.pop()
            self.forget()

    def displayhook(self, obj):
        """Custom displayhook for the exec in default(), which prevents
        assignment of the _ variable in the builtins.
        """
        # reproduce the behavior of the standard displayhook, not printing None
        if obj is not None:
            self.message(repr(obj))

    @contextmanager
    def _enable_multiline_input(self):
        try:
            import readline
        except ImportError:
            yield
            return

        def input_auto_indent():
            last_index = readline.get_current_history_length()
            last_line = readline.get_history_item(last_index)
            if last_line:
                if last_line.isspace():
                    # If the last line is empty, we don't need to indent
                    return

                last_line = last_line.rstrip('\r\n')
                indent = len(last_line) - len(last_line.lstrip())
                if last_line.endswith(":"):
                    indent += 4
                readline.insert_text(' ' * indent)

        completenames = self.completenames
        try:
            self.completenames = self.complete_multiline_names
            readline.set_startup_hook(input_auto_indent)
            yield
        finally:
            readline.set_startup_hook()
            self.completenames = completenames
        return

    def _exec_in_closure(self, source, globals, locals):
        """ Run source code in closure so code object created within source
            can find variables in locals correctly

            returns True if the source is executed, False otherwise
        """

        # Determine if the source should be executed in closure. Only when the
        # source compiled to multiple code objects, we should use this feature.
        # Otherwise, we can just raise an exception and normal exec will be used.

        code = compile(source, "<string>", "exec")
        if not any(isinstance(const, CodeType) for const in code.co_consts):
            return False

        # locals could be a proxy which does not support pop
        # copy it first to avoid modifying the original locals
        locals_copy = dict(locals)

        locals_copy["__pdb_eval__"] = {
            "result": None,
            "write_back": {}
        }

        # If the source is an expression, we need to print its value
        try:
            compile(source, "<string>", "eval")
        except SyntaxError:
            pass
        else:
            source = "__pdb_eval__['result'] = " + source

        # Add write-back to update the locals
        source = ("try:\n" +
                  textwrap.indent(source, "  ") + "\n" +
                  "finally:\n" +
                  "  __pdb_eval__['write_back'] = locals()")

        # Build a closure source code with freevars from locals like:
        # def __pdb_outer():
        #   var = None
        #   def __pdb_scope():  # This is the code object we want to execute
        #     nonlocal var
        #     <source>
        #   return __pdb_scope.__code__
        source_with_closure = ("def __pdb_outer():\n" +
                               "\n".join(f"  {var} = None" for var in locals_copy) + "\n" +
                               "  def __pdb_scope():\n" +
                               "\n".join(f"    nonlocal {var}" for var in locals_copy) + "\n" +
                               textwrap.indent(source, "    ") + "\n" +
                               "  return __pdb_scope.__code__"
                               )

        # Get the code object of __pdb_scope()
        # The exec fills locals_copy with the __pdb_outer() function and we can call
        # that to get the code object of __pdb_scope()
        ns = {}
        try:
            exec(source_with_closure, {}, ns)
        except Exception:
            return False
        code = ns["__pdb_outer"]()

        cells = tuple(types.CellType(locals_copy.get(var)) for var in code.co_freevars)

        try:
            exec(code, globals, locals_copy, closure=cells)
        except Exception:
            return False

        # get the data we need from the statement
        pdb_eval = locals_copy["__pdb_eval__"]

        # __pdb_eval__ should not be updated back to locals
        pdb_eval["write_back"].pop("__pdb_eval__")

        # Write all local variables back to locals
        locals.update(pdb_eval["write_back"])
        eval_result = pdb_eval["result"]
        if eval_result is not None:
            self.message(repr(eval_result))

        return True

    def _exec_await(self, source, globals, locals):
        """ Run source code that contains await by playing with async shim frame"""
        # Put the source in an async function
        source_async = (
            "async def __pdb_await():\n" +
            textwrap.indent(source, "    ") + '\n' +
            "    __pdb_locals.update(locals())"
        )
        ns = globals | locals
        # We use __pdb_locals to do write back
        ns["__pdb_locals"] = locals
        exec(source_async, ns)
        self.async_awaitable = ns["__pdb_await"]()

    def _read_code(self, line):
        buffer = line
        is_await_code = False
        code = None
        try:
            if (code := codeop.compile_command(line + '\n', '<stdin>', 'single')) is None:
                # Multi-line mode
                with self._enable_multiline_input():
                    buffer = line
                    continue_prompt = "...   "
                    while (code := codeop.compile_command(buffer, '<stdin>', 'single')) is None:
                        if self.use_rawinput:
                            try:
                                line = input(continue_prompt)
                            except (EOFError, KeyboardInterrupt):
                                self.lastcmd = ""
                                print('\n')
                                return None, None, False
                        else:
                            self.stdout.write(continue_prompt)
                            self.stdout.flush()
                            line = self.stdin.readline()
                            if not len(line):
                                self.lastcmd = ""
                                self.stdout.write('\n')
                                self.stdout.flush()
                                return None, None, False
                            else:
                                line = line.rstrip('\r\n')
                        if line.isspace():
                            # empty line, just continue
                            buffer += '\n'
                        else:
                            buffer += '\n' + line
                    self.lastcmd = buffer
        except SyntaxError as e:
            # Maybe it's an await expression/statement
            if (
                self.async_shim_frame is not None
                and e.msg == "'await' outside function"
            ):
                is_await_code = True
            else:
                raise

        return code, buffer, is_await_code

    def default(self, line):
        if line[:1] == '!': line = line[1:].strip()
        locals = self.curframe.f_locals
        globals = self.curframe.f_globals
        try:
            code, buffer, is_await_code = self._read_code(line)
            if buffer is None:
                return
            save_stdout = sys.stdout
            save_stdin = sys.stdin
            save_displayhook = sys.displayhook
            try:
                sys.stdin = self.stdin
                sys.stdout = self.stdout
                sys.displayhook = self.displayhook
                if is_await_code:
                    self._exec_await(buffer, globals, locals)
                    return True
                else:
                    if not self._exec_in_closure(buffer, globals, locals):
                        exec(code, globals, locals)
            finally:
                sys.stdout = save_stdout
                sys.stdin = save_stdin
                sys.displayhook = save_displayhook
        except:
            self._error_exc()

    def _replace_convenience_variables(self, line):
        """Replace the convenience variables in 'line' with their values.
           e.g. $foo is replaced by __pdb_convenience_variables["foo"].
           Note: such pattern in string literals will be skipped"""

        if "$" not in line:
            return line

        dollar_start = dollar_end = (-1, -1)
        replace_variables = []
        try:
            for t in tokenize.generate_tokens(io.StringIO(line).readline):
                token_type, token_string, start, end, _ = t
                if token_type == token.OP and token_string == '$':
                    dollar_start, dollar_end = start, end
                elif start == dollar_end and token_type == token.NAME:
                    # line is a one-line command so we only care about column
                    replace_variables.append((dollar_start[1], end[1], token_string))
        except tokenize.TokenError:
            return line

        if not replace_variables:
            return line

        last_end = 0
        line_pieces = []
        for start, end, name in replace_variables:
            line_pieces.append(line[last_end:start] + f'__pdb_convenience_variables["{name}"]')