pdb.py

"""
pdb++, a drop-in replacement for pdb
====================================

This module extends the stdlib pdb in numerous ways: look at the README for
more details on pdb++ features.
"""

from __future__ import print_function

import sys
import os.path
import inspect
import code
import codecs
import contextlib
import types
import traceback
import subprocess
import threading
import pprint
import re
import signal
from collections import OrderedDict

import fancycompleter
import six
from fancycompleter import Color, Completer, ConfigurableClass

__author__ = 'Antonio Cuni <anto.cuni@gmail.com>'
__url__ = 'http://github.com/antocuni/pdb'
__version__ = fancycompleter.LazyVersion('pdbpp')

try:
    from inspect import signature  # Python >= 3.3
except ImportError:
    try:
        from funcsigs import signature
    except ImportError:
        def signature(obj):
            return ' [pip install funcsigs to show the signature]'


# If it contains only _, digits, letters, [] or dots, it's probably side
# effects free.
side_effects_free = re.compile(r'^ *[_0-9a-zA-Z\[\].]* *$')

RE_COLOR_ESCAPES = re.compile("(\x1b.*?m)*")

if sys.version_info < (3, ):
    from io import BytesIO as StringIO
else:
    from io import StringIO


local = threading.local()
local.GLOBAL_PDB = None
local._pdbpp_completing = False


def __getattr__(name):
    """Backward compatibility (Python 3.7+)"""
    if name == "GLOBAL_PDB":
        return local.GLOBAL_PDB
    raise AttributeError


def import_from_stdlib(name):
    import code  # arbitrary module which stays in the same dir as pdb
    result = types.ModuleType(name)

    stdlibdir, _ = os.path.split(code.__file__)
    pyfile = os.path.join(stdlibdir, name + '.py')
    with open(pyfile) as f:
        src = f.read()
    co_module = compile(src, pyfile, 'exec', dont_inherit=True)
    exec(co_module, result.__dict__)

    return result


pdb = import_from_stdlib('pdb')


def rebind_globals(func, newglobals):
    newfunc = types.FunctionType(func.__code__, newglobals, func.__name__,
                                 func.__defaults__, func.__closure__)
    if sys.version_info >= (3, ):
        newfunc.__annotations__ = func.__annotations__
        newfunc.__kwdefaults__ = func.__kwdefaults__
    return newfunc


class DefaultConfig(object):
    prompt = '(Pdb++) '
    highlight = True
    sticky_by_default = False
    bg = 'dark'
    use_pygments = True
    colorscheme = None
    use_terminal256formatter = None  # Defaults to `"256color" in $TERM`.
    editor = None  # Autodetected if unset.
    stdin_paste = None       # for emacs, you can use my bin/epaste script
    truncate_long_lines = True
    exec_if_unfocused = None
    disable_pytest_capturing = False
    encodings = ('utf-8', 'latin-1')

    enable_hidden_frames = True
    show_hidden_frames_count = True

    line_number_color = Color.turquoise
    filename_color = Color.yellow
    current_line_color = "39;49;7"  # default fg, bg, inversed

    show_traceback_on_error = True
    show_traceback_on_error_limit = None

    # Default keyword arguments passed to ``Pdb`` constructor.
    default_pdb_kwargs = {
    }

    def setup(self, pdb):
        pass

    def before_interaction_hook(self, pdb):
        pass


def setbgcolor(line, color):
    # hack hack hack
    # add a bgcolor attribute to all escape sequences found
    import re
    setbg = '\x1b[%sm' % color
    regexbg = '\\1;%sm' % color
    result = setbg + re.sub('(\x1b\\[.*?)m', regexbg, line) + '\x1b[00m'
    if os.environ.get('TERM') == 'eterm-color':
        # it seems that emacs' terminal has problems with some ANSI escape
        # sequences. Eg, 'ESC[44m' sets the background color in all terminals
        # I tried, but not in emacs. To set the background color, it needs to
        # have also an explicit foreground color, e.g. 'ESC[37;44m'. These
        # three lines are a hack, they try to add a foreground color to all
        # escape sequences wich are not recognized by emacs. However, we need
        # to pick one specific fg color: I choose white (==37), but you might
        # want to change it.  These lines seems to work fine with the ANSI
        # codes produced by pygments, but they are surely not a general
        # solution.
        result = result.replace(setbg, '\x1b[37;%dm' % color)
        result = result.replace('\x1b[00;%dm' % color, '\x1b[37;%dm' % color)
        result = result.replace('\x1b[39;49;00;', '\x1b[37;')
    return result


CLEARSCREEN = '\033[2J\033[1;1H'


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


class Undefined:
    def __repr__(self):
        return '<undefined>'


undefined = Undefined()


class PdbMeta(type):
    def __call__(cls, *args, **kwargs):
        """Reuse an existing instance with ``pdb.set_trace()``."""
        global_pdb = getattr(local, "GLOBAL_PDB", None)
        in_interaction = global_pdb and global_pdb._in_interaction
        use_global_pdb = kwargs.pop("use_global_pdb", not in_interaction)

        frame = sys._getframe().f_back
        called_for_set_trace = False
        while frame:
            if (frame.f_code.co_name == "set_trace"
                    and frame.f_back
                    and "set_trace" in frame.f_back.f_code.co_names):
                called_for_set_trace = frame
                break
            frame = frame.f_back

        same_class = global_pdb and cls.consider_as_same_class(global_pdb, cls)
        if use_global_pdb and same_class and called_for_set_trace:
            if hasattr(global_pdb, "botframe"):
                # Do not stop while tracing is active (in _set_stopinfo).
                # But skip it with instances that have not called set_trace
                # before.
                global_pdb.set_continue()
            return global_pdb

        obj = cls.__new__(cls)
        if called_for_set_trace:
            kwargs.setdefault("start_filename", called_for_set_trace.f_code.co_filename)
            kwargs.setdefault("start_lineno", called_for_set_trace.f_lineno)

        set_global_pdb = kwargs.pop("set_global_pdb", use_global_pdb)
        obj.__init__(*args, **kwargs)
        if set_global_pdb:
            local.GLOBAL_PDB = obj
        return obj

    @classmethod
    def consider_as_same_class(cls, obj, C):
        if isinstance(obj, C):
            return True
        if sys.version_info < (3, 3):
            return inspect.getsourcelines(obj.__class__) == inspect.getsourcelines(C)
        return C.__qualname__ == obj.__class__.__qualname__


@six.add_metaclass(PdbMeta)
class Pdb(pdb.Pdb, ConfigurableClass, object):

    DefaultConfig = DefaultConfig
    config_filename = '.pdbrc.py'
    disabled = False
    fancycompleter = None

    _in_interaction = False

    def __init__(self, *args, **kwds):
        self.ConfigFactory = kwds.pop('Config', None)
        self.start_lineno = kwds.pop('start_lineno', None)
        self.start_filename = kwds.pop('start_filename', None)
        self.config = self.get_config(self.ConfigFactory)
        self.config.setup(self)
        if self.config.disable_pytest_capturing:
            self._disable_pytest_capture_maybe()
        kwargs = self.config.default_pdb_kwargs.copy()
        kwargs.update(**kwds)
        super(Pdb, self).__init__(*args, **kwargs)
        self.prompt = self.config.prompt
        self.display_list = {}  # frame --> (name --> last seen value)
        self.sticky = self.config.sticky_by_default
        self.first_time_sticky = self.sticky
        self.sticky_ranges = {}  # frame --> (start, end)
        self.tb_lineno = {}  # frame --> lineno where the exception raised
        self.history = []
        self.show_hidden_frames = False
        self.hidden_frames = []
        self.stdout = self.ensure_file_can_write_unicode(self.stdout)

    def ensure_file_can_write_unicode(self, f):
        # Wrap with an encoder, but only if not already wrapped
        if (not hasattr(f, 'stream')
                and getattr(f, 'encoding', False)
                and f.encoding.lower() != 'utf-8'):
            f = codecs.getwriter('utf-8')(getattr(f, 'buffer', f))

        return f

    def _disable_pytest_capture_maybe(self):
        try:
            import py.test
            # Force raising of ImportError if pytest is not installed.
            py.test.config
        except (ImportError, AttributeError):
            return
        try:
            capman = py.test.config.pluginmanager.getplugin('capturemanager')
            capman.suspendcapture()
        except KeyError:
            pass
        except AttributeError:
            # Newer pytest with support ready, or very old py.test for which
            # this hack does not work.
            pass

    def interaction(self, frame, traceback):
        self._in_interaction = True
        try:
            return self._interaction(frame, traceback)
        finally:
            self._in_interaction = False

    def _interaction(self, frame, traceback):
        # Restore the previous signal handler at the Pdb prompt.
        if getattr(pdb.Pdb, '_previous_sigint_handler', None):
            try:
                signal.signal(signal.SIGINT, pdb.Pdb._previous_sigint_handler)
            except ValueError:  # ValueError: signal only works in main thread
                pass
            else:
                pdb.Pdb._previous_sigint_handler = None
        ret = self.setup(frame, traceback)
        if ret:
            # no interaction desired at this time (happens if .pdbrc contains
            # a command like "continue")
            self.forget()
            return
        if self.config.exec_if_unfocused:
            self.exec_if_unfocused()
        self.print_stack_entry(self.stack[self.curindex])
        self.print_hidden_frames_count()

        with self._custom_completer():
            self.config.before_interaction_hook(self)
            # Use _cmdloop on py3 which catches KeyboardInterrupt.
            if hasattr(self, '_cmdloop'):
                self._cmdloop()
            else:
                self.cmdloop()

        self.forget()

    @contextlib.contextmanager
    def _custom_completer(self):
        if not self.fancycompleter:
            self.fancycompleter = fancycompleter.setup()

        readline_ = self.fancycompleter.config.readline
        old_completer = readline_.get_completer()
        readline_.set_completer(self.complete)
        self._lastcompstate = [None, 0]
        try:
            yield
        finally:
            readline_.set_completer(old_completer)

    def print_hidden_frames_count(self):
        n = len(self.hidden_frames)
        if n and self.config.show_hidden_frames_count:
            plural = n > 1 and "s" or ""
            print(
                "   %d frame%s hidden (try 'help hidden_frames')" % (n, plural),
                file=self.stdout,
            )

    def exec_if_unfocused(self):
        import os
        import wmctrl
        term = os.getenv('TERM', '')
        try:
            winid = int(os.getenv('WINDOWID'))
        except (TypeError, ValueError):
            return  # cannot find WINDOWID of the terminal
        active_win = wmctrl.Window.get_active()
        if not active_win or (int(active_win.id, 16) != winid) and \
           not (active_win.wm_class == 'emacs.Emacs' and term.startswith('eterm')):
            os.system(self.config.exec_if_unfocused)

    def setup(self, frame, tb):
        ret = super(Pdb, self).setup(frame, tb)
        if not ret:
            while tb:
                lineno = lasti2lineno(tb.tb_frame.f_code, tb.tb_lasti)
                self.tb_lineno[tb.tb_frame] = lineno
                tb = tb.tb_next
        return ret

    def _is_hidden(self, frame):
        if not self.config.enable_hidden_frames:
            return False

        # Decorated code is always considered to be hidden.
        consts = frame.f_code.co_consts
        if consts and consts[-1] is _HIDE_FRAME:
            return True

        # Do not hide if this frame contains the initial set_trace.
        if frame is getattr(self, "_via_set_trace_frame", None):
            return False

        if frame.f_globals.get('__unittest'):
            return True
        if frame.f_locals.get('__tracebackhide__') \
           or frame.f_globals.get('__tracebackhide__'):
            return True

    def get_stack(self, f, t):
        # show all the frames, except the ones that explicitly ask to be hidden
        fullstack, idx = super(Pdb, self).get_stack(f, t)
        self.fullstack = fullstack
        return self.compute_stack(fullstack, idx)

    def compute_stack(self, fullstack, idx=None):
        if idx is None:
            idx = len(fullstack) - 1
        if self.show_hidden_frames:
            return fullstack, idx

        self.hidden_frames = []
        newstack = []
        for frame, lineno in fullstack:
            if self._is_hidden(frame):
                self.hidden_frames.append((frame, lineno))
            else:
                newstack.append((frame, lineno))
        newidx = idx - len(self.hidden_frames)
        return newstack, newidx

    def refresh_stack(self):
        """
        Recompute the stack after e.g. show_hidden_frames has been modified
        """
        self.stack, _ = self.compute_stack(self.fullstack)
        # find the current frame in the new stack
        for i, (frame, _) in enumerate(self.stack):
            if frame is self.curframe:
                self.curindex = i
                break
        else:
            self.curindex = len(self.stack)-1
            self.curframe = self.stack[-1][0]
            self.print_current_stack_entry()

    def forget(self):
        if not getattr(local, "_pdbpp_completing", False):
            super(Pdb, self).forget()

    @classmethod
    def _get_all_completions(cls, complete, text):
        r = []
        i = 0
        while True:
            comp = complete(text, i)
            if comp is None:
                break
            i += 1
            r.append(comp)
        return r

    @contextlib.contextmanager
    def _patch_readline_for_pyrepl(self):
        """Patch readline module used in original Pdb.complete."""
        uses_pyrepl = self.fancycompleter.config.readline != sys.modules["readline"]

        if not uses_pyrepl:
            yield
            return

        # Make pdb.Pdb.complete use pyrepl's readline.
        orig_readline = sys.modules["readline"]
        sys.modules["readline"] = self.fancycompleter.config.readline
        try:
            yield
        finally:
            sys.modules["readline"] = orig_readline

    def complete(self, text, state):
        """Handle completions from fancycompleter and original pdb."""
        if state == 0:
            local._pdbpp_completing = True

            self._completions = []

            # Get completions from original pdb.
            with self._patch_readline_for_pyrepl():
                real_pdb = super(Pdb, self)
                for x in self._get_all_completions(real_pdb.complete, text):
                    if x not in self._completions:
                        self._completions.append(x)

            # Get completions from fancycompleter.
            mydict = self.curframe.f_globals.copy()
            mydict.update(self.curframe_locals)
            completer = Completer(mydict)
            completions = self._get_all_completions(completer.complete, text)

            # Ignore "\t" as only completion from fancycompleter, if there are
            # pdb completions, and remove duplicate completions.
            if completions and (completions != ["\t"] or not len(self._completions)):
                RE_REMOVE_ESCAPE_SEQS = re.compile(r"\x1b\[[\d;]+m")
                clean_fancy_completions = set([
                    RE_REMOVE_ESCAPE_SEQS.sub("", x) for x in completions
                ])
                self._completions = [
                    x for x in self._completions
                    if x not in clean_fancy_completions
                ]
                self._completions.extend(completions)

            self._filter_completions(text)

            local._pdbpp_completing = False

        try:
            return self._completions[state]
        except IndexError:
            return None

    def _filter_completions(self, text):
        # Remove anything prefixed with "_" / "__" by default, but only
        # display it on additional request (3rd tab, after pyrepl's "[not
        # unique]"), or if the prefix is used already.
        if text == self._lastcompstate[0]:
            if self._lastcompstate[1] > 0:
                return
            self._lastcompstate[1] += 1
        else:
            self._lastcompstate[0] = text
            self._lastcompstate[1] = 0

        if text[-1:] != "_":
            self._completions = [
                x
                for x in self._completions
                if RE_COLOR_ESCAPES.sub("", x)[:1] != "_"
            ]
        elif text[-2:] != "__":
            self._completions = [
                x
                for x in self._completions
                if RE_COLOR_ESCAPES.sub("", x)[:2] != "__"
            ]

    def _init_pygments(self):
        if not self.config.use_pygments:
            return False

        if hasattr(self, '_fmt'):
            return True

        try:
            from pygments.lexers import PythonLexer
            from pygments.formatters import TerminalFormatter, Terminal256Formatter
        except ImportError:
            return False

        if hasattr(self.config, 'formatter'):
            self._fmt = self.config.formatter
        else:
            if (self.config.use_terminal256formatter
                    or (self.config.use_terminal256formatter is None
                        and "256color" in os.environ.get("TERM", ""))):
                Formatter = Terminal256Formatter
            else:
                Formatter = TerminalFormatter
            self._fmt = Formatter(bg=self.config.bg,
                                  colorscheme=self.config.colorscheme)
        self._lexer = PythonLexer(stripnl=False)
        return True

    stack_entry_regexp = re.compile(r'(.*?)\(([0-9]+?)\)(.*)', re.DOTALL)

    def format_stack_entry(self, frame_lineno, lprefix=': '):
        entry = super(Pdb, self).format_stack_entry(frame_lineno, lprefix)
        entry = self.try_to_decode(entry)
        if self.config.highlight:
            match = self.stack_entry_regexp.match(entry)
            if match:
                filename, lineno, other = match.groups()
                filename = Color.set(self.config.filename_color, filename)
                lineno = Color.set(self.config.line_number_color, lineno)
                entry = '%s(%s)%s' % (filename, lineno, other)
        if self.config.use_pygments:
            loc, _, source = entry.rpartition(lprefix)
            if _:
                entry = loc + _ + self.format_source(source).rstrip()
        return entry

    def try_to_decode(self, s):
        for encoding in self.config.encodings:
            try:
                return s.decode(encoding)
            except (UnicodeDecodeError, AttributeError):
                pass
        return s

    def format_source(self, src):
        if not self._init_pygments():
            return src
        from pygments import highlight
        src = self.try_to_decode(src)
        return highlight(src, self._lexer, self._fmt)

    def _format_line(self, lineno, marker, line, lineno_width):
        lineno = ('%%%dd' % lineno_width) % lineno
        if self.config.highlight:
            lineno = Color.set(self.config.line_number_color, lineno)
        line = '%s  %2s %s' % (lineno, marker, line)
        if self.config.highlight and marker == '->':
            if self.config.current_line_color:
                line = setbgcolor(line, self.config.current_line_color)
        return line

    def execRcLines(self):
        self._pdbpp_executing_rc_lines = True
        try:
            return super(Pdb, self).execRcLines()
        finally:
            del self._pdbpp_executing_rc_lines

    def parseline(self, line):
        if getattr(self, "_pdbpp_executing_rc_lines", False):
            return super(Pdb, self).parseline(line)

        if line.startswith('!!'):
            # Force the "standard" behaviour, i.e. first check for the
            # command, then for the variable name to display.
            line = line[2:]
            return super(Pdb, self).parseline(line)

        if line.endswith('?') and not line.startswith("!"):
            arg = line.split('?', 1)[0]
            if line.endswith('??'):
                cmd = 'source'
                self.do_inspect(arg)
                self.stdout.write('%-28s\n' % Color.set(Color.red, 'Source:'))
            elif (hasattr(self, 'do_' + arg)
                    and arg not in self.curframe.f_globals
                    and arg not in self.curframe_locals):
                cmd = "help"
            else:
                cmd = "inspect"
            return cmd, arg, line

        # pdb++ "smart command mode": don't execute commands if a variable
        # with the name exists in the current context;
        # This prevents pdb to quit if you type e.g. 'r[0]' by mystake.
        cmd, arg, newline = super(Pdb, self).parseline(line)

        if cmd:
            # prefixed strings.
            if (
                cmd in ("b", "f", "r", "u")
                and len(newline) > 1
                and (newline[1] == "'" or newline[1] == '"')
            ):
                cmd, arg, newline = None, None, line

            elif hasattr(self, "do_" + cmd):
                if (
                    self.curframe
                    and (cmd in self.curframe.f_globals or cmd in self.curframe_locals)
                ) or arg.startswith("="):
                    cmd, arg, newline = None, None, line
                elif cmd == "list" and arg.startswith("("):
                    # heuristic: handle "list(..." as the builtin.
                    cmd, arg, newline = None, None, line

        # Fix cmd to not be None when used in completions.
        # This would trigger a TypeError (instead of AttributeError) in
        # Cmd.complete (https://bugs.python.org/issue35270).
        if cmd is None:
            f = sys._getframe()
            while f.f_back:
                f = f.f_back
                if f.f_code.co_name == "complete":
                    cmd = ""
                    break

        return cmd, arg, newline

    def do_inspect(self, arg):
        obj = self._getval(arg)

        data = OrderedDict()
        data['Type'] = type(obj).__name__
        data['String Form'] = str(obj).strip()
        try:
            data['Length'] = len(obj)
        except TypeError:
            pass
        try:
            data['File'] = inspect.getabsfile(obj)
        except TypeError:
            pass

        if (isinstance(obj, type)
                and hasattr(obj, '__init__')
                and getattr(obj, '__module__') != '__builtin__'):
            # Class - show definition and docstring for constructor
            data['Docstring'] = obj.__doc__
            data['Constructor information'] = ''
            try:
                data[' Definition'] = '%s%s' % (arg, signature(obj))
            except ValueError:
                pass
            data[' Docstring'] = obj.__init__.__doc__
        else:
            try:
                data['Definition'] = '%s%s' % (arg, signature(obj))
            except (TypeError, ValueError):
                pass
            data['Docstring'] = obj.__doc__

        for key, value in data.items():
            formatted_key = Color.set(Color.red, key + ':')
            self.stdout.write('%-28s %s\n' % (formatted_key, value))

    def default(self, line):
        self.history.append(line)
        return super(Pdb, self).default(line)

    def do_help(self, arg):
        try:
            return super(Pdb, self).do_help(arg)
        except AttributeError:
            print("*** No help for '{command}'".format(command=arg),
                  file=self.stdout)
    do_help.__doc__ = pdb.Pdb.do_help.__doc__

    def help_hidden_frames(self):
        print("""\
Some frames might be marked as "hidden": by default, hidden frames are not
shown in the stack trace, and cannot be reached using ``up`` and ``down``.
You can use ``hf_unhide`` to tell pdb++ to ignore the hidden status (i.e., to
treat hidden frames as normal ones), and ``hf_hide`` to hide them again.
``hf_list`` prints a list of hidden frames.

Frames can be marked as hidden in the following ways:

- by using the ``@pdb.hideframe`` function decorator

- by having ``__tracebackhide__=True`` in the locals or the globals of the
  function (this is used by pytest)

- by having ``__unittest=True`` in the globals of the function (this hides
  unittest internal stuff)

- by providing a list of skip patterns to the Pdb class constructor.  This
  list defaults to ``skip=["importlib._bootstrap"]``.

Note that the initial frame where ``set_trace`` was called from is not hidden,
except for when using the function decorator.
""", file=self.stdout)

    def do_hf_unhide(self, arg):
        """
        {hf_show}
        unhide hidden frames, i.e. make it possible to ``up`` or ``down``
        there
        """
        self.show_hidden_frames = True
        self.refresh_stack()

    def do_hf_hide(self, arg):
        """
        {hf_hide}
        (re)hide hidden frames, if they have been unhidden by ``hf_unhide``
        """
        self.show_hidden_frames = False
        self.refresh_stack()

    def do_hf_list(self, arg):
        for frame_lineno in self.hidden_frames:
            print(self.format_stack_entry(frame_lineno, pdb.line_prefix),
                  file=self.stdout)

    def do_longlist(self, arg):
        """
        {longlist|ll}
        List source code for the current function.

        Differently than list, the whole function is displayed; the
        current line is marked with '->'.  In case of post-mortem
        debugging, the line which effectively raised the exception is
        marked with '>>'.

        If the 'highlight' config option is set and pygments is
        installed, the source code is colorized.
        """
        self.lastcmd = 'longlist'
        self._printlonglist()

    do_ll = do_longlist

    def _printlonglist(self, linerange=None):
        try:
            if self.curframe.f_code.co_name == '<module>':
                # inspect.getsourcelines is buggy in this case: if we just
                # pass the frame, it returns the source for the first function
                # defined in the module.  Instead, we want the full source
                # code of the module
                lines, _ = inspect.findsource(self.curframe)
                lineno = 1
            else:
                try:
                    lines, lineno = inspect.getsourcelines(self.curframe)
                except Exception as e:
                    print('** Error in inspect.getsourcelines: %s **' %
                          e, file=self.stdout)
                    return
        except IOError as e:
            print('** Error: %s **' % e, file=self.stdout)
            return
        if linerange:
            start, end = linerange
            start = max(start, lineno)
            end = min(end, lineno+len(lines))
            lines = lines[start-lineno:end-lineno]
            lineno = start
        self._print_lines_pdbpp(lines, lineno)

    def _print_lines_pdbpp(self, lines, lineno, print_markers=True):
        lines = [line[:-1] for line in lines]  # remove the trailing '\n'
        lines = [line.replace('\t', '    ')
                 for line in lines]  # force tabs to 4 spaces
        width, height = self.get_terminal_size()

        if self.config.truncate_long_lines:
            maxlength = max(width - 9, 16)
            lines = [line[:maxlength] for line in lines]
        else:
            maxlength = max(map(len, lines))

        if print_markers:
            exc_lineno = self.tb_lineno.get(self.curframe, None)
            if height >= 6:
                last_marker_line = max(
                    self.curframe.f_lineno,
                    exc_lineno if exc_lineno else 0) - lineno
                if last_marker_line >= 0:
                    maxlines = last_marker_line + height * 2 // 3
                    if len(lines) > maxlines:
                        lines = lines[:maxlines]
                        lines.append('...')

        if self.config.highlight and print_markers:
            # Fill with spaces.  This is important for setbgcolor, although
            # only for the current/marked line really.
            lines = [line.ljust(maxlength) for line in lines]

        if self.config.use_pygments:
            src = self.format_source('\n'.join(lines))
            lines = src.splitlines()

        lineno_width = len(str(lineno + len(lines)))
        if print_markers:
            for i, line in enumerate(lines):
                if lineno == self.curframe.f_lineno:
                    marker = '->'
                elif lineno == exc_lineno:
                    marker = '>>'
                else:
                    marker = ''
                lines[i] = self._format_line(lineno, marker, line, lineno_width)
                lineno += 1
        else:
            for i, line in enumerate(lines):
                lines[i] = self._format_line(lineno, '', line, lineno_width)
                lineno += 1
        print('\n'.join(lines), file=self.stdout)

    def _format_source_lines(self, lines):
        if not lines:
            return lines

        if not self.config.use_pygments and not self.config.highlight:
            return lines

        # Format source without prefixes added by pdb, including line numbers.
        prefixes = []
        src_lines = []

        for x in lines:
            prefix, _, src = x.partition('\t')
            prefixes.append(prefix)
            src_lines.append(src)
        formatted_src_lines = self.format_source(
            "\n".join(src_lines) + "\n"
        ).splitlines()

        RE_LNUM_PREFIX = re.compile(r"^\d+")
        if self.config.highlight:
            prefixes = [
                RE_LNUM_PREFIX.sub(
                    lambda m: Color.set(self.config.line_number_color, m.group(0)),
                    prefix
                )
                for prefix in prefixes
            ]

        return [
            "%s\t%s" % (prefix, src)
            for (prefix, src) in zip(prefixes, formatted_src_lines)
        ]

    if sys.version_info >= (3, 2):
        def _print_lines(self, lines, *args, **kwargs):
            """Enhance original _print_lines with highlighting.

            Used via do_list currently only, do_source and do_longlist are
            overridden.
            """
            if not lines or not (self.config.use_pygments or self.config.highlight):
                return super(Pdb, self)._print_lines(lines, *args, **kwargs)

            oldstdout = self.stdout
            self.stdout = StringIO()
            ret = super(Pdb, self)._print_lines(lines, *args, **kwargs)
            orig_pdb_lines = self.stdout.getvalue().splitlines()
            self.stdout = oldstdout

            for line in self._format_source_lines(orig_pdb_lines):
                print(line, file=self.stdout)
            return ret
    else:
        # Only for Python 2.7, where _print_lines is not used/available.
        def do_list(self, arg):
            if not (self.config.use_pygments or self.config.highlight):
                return super(Pdb, self).do_list(arg)

            oldstdout = self.stdout
            self.stdout = StringIO()
            ret = super(Pdb, self).do_list(arg)
            orig_pdb_lines = self.stdout.getvalue().splitlines()
            self.stdout = oldstdout

            for line in self._format_source_lines(orig_pdb_lines):
                print(line, file=self.stdout)
            return ret

        do_list.__doc__ = pdb.Pdb.do_list.__doc__
        do_l = do_list

    def do_continue(self, arg):
        if arg != '':
            self.do_tbreak(arg)
        return super(Pdb, self).do_continue('')
    do_continue.__doc__ = pdb.Pdb.do_continue.__doc__
    do_c = do_cont = do_continue

    def do_p(self, arg):
        """p expression
        Print the value of the expression.
        """
        try:
            val = self._getval(arg)
        except:
            return
        try:
            self.message(repr(val))
        except:
            exc_info = sys.exc_info()[:2]
            self.error(traceback.format_exception_only(*exc_info)[-1].strip())

    def do_pp(self, arg):
        try:
            val = self._getval(arg)
        except:
            pass
        try:
            width, height = self.get_terminal_size()
            pprint.pprint(val, self.stdout, width=width)
        except:
            exc_info = sys.exc_info()[:2]
            self.error(traceback.format_exception_only(*exc_info)[-1].strip())
    do_pp.__doc__ = pdb.Pdb.do_pp.__doc__

    def do_debug(self, arg):
        # this is a hack (as usual :-))
        #
        # inside the original do_debug, there is a call to the global "Pdb" to
        # instantiate the recursive debugger: we want to intercept this call
        # and instantiate *our* Pdb, passing our custom config. Therefore we
        # dynamically rebind the globals.
        Config = self.ConfigFactory

        class PdbppWithConfig(self.__class__):
            def __init__(self_withcfg, *args, **kwargs):
                kwargs.setdefault("Config", Config)
                super(PdbppWithConfig, self_withcfg).__init__(*args, **kwargs)

                # Backport of fix for bpo-31078 (not yet merged).
                self_withcfg.use_rawinput = self.use_rawinput

                local.GLOBAL_PDB = self_withcfg

        if sys.version_info < (3, ):
            do_debug_func = pdb.Pdb.do_debug.im_func
        else:
            do_debug_func = pdb.Pdb.do_debug

        newglobals = do_debug_func.__globals__.copy()
        newglobals['Pdb'] = PdbppWithConfig
        new_do_debug = rebind_globals(do_debug_func, newglobals)

        # Handle any exception, e.g. SyntaxErrors.
        # This is about to be improved in Python itself (3.8, 3.7.3?).
        prev_pdb = local.GLOBAL_PDB
        try:
            with self._custom_completer():
                return new_do_debug(self, arg)
        except Exception:
            exc_info = sys.exc_info()[:2]
            msg = traceback.format_exception_only(*exc_info)[-1].strip()
            self.error(msg)
        finally:
            local.GLOBAL_PDB = prev_pdb

    do_debug.__doc__ = pdb.Pdb.do_debug.__doc__

    def do_interact(self, arg):
        """
        interact

        Start an interative interpreter whose global namespace
        contains all the names found in the current scope.
        """
        ns = self.curframe.f_globals.copy()
        ns.update(self.curframe_locals)
        code.interact("*interactive*", local=ns)

    def do_track(self, arg):
        """
        track expression

        Display a graph showing which objects are referred by the
        value of the expression.  This command requires pypy to be in
        the current PYTHONPATH.
        """
        try:
            from rpython.translator.tool.reftracker import track
        except ImportError:
            print('** cannot import pypy.translator.tool.reftracker **',
                  file=self.stdout)
            return
        try:
            val = self._getval(arg)
        except:
            pass
        else:
            track(val)

    def _get_display_list(self):
        return self.display_list.setdefault(self.curframe, {})

    def _getval_or_undefined(self, arg):
        try:
            return eval(arg, self.curframe.f_globals,
                        self.curframe_locals)
        except NameError:
            return undefined

    def do_display(self, arg):
        """
        display expression

        Add expression to the display list; expressions in this list
        are evaluated at each step, and printed every time its value
        changes.

        WARNING: since the expressions is evaluated multiple time, pay
        attention not to put expressions with side-effects in the
        display list.
        """
        try:
            value = self._getval_or_undefined(arg)
        except:
            return
        self._get_display_list()[arg] = value

    def do_undisplay(self, arg):
        """
        undisplay expression

        Remove expression from the display list.
        """
        try:
            del self._get_display_list()[arg]
        except KeyError:
            print('** %s not in the display list **' % arg, file=self.stdout)

    def _print_if_sticky(self):
        if self.sticky:
            if self.first_time_sticky:
                self.first_time_sticky = False
            else:
                self.stdout.write(CLEARSCREEN)
            frame, lineno = self.stack[self.curindex]
            filename = self.canonic(frame.f_code.co_filename)
            s = '> %s(%r)' % (filename, lineno)
            print(s, file=self.stdout)
            print(file=self.stdout)
            sticky_range = self.sticky_ranges.get(self.curframe, None)
            self._printlonglist(sticky_range)

            if '__exception__' in frame.f_locals:
                s = self._format_exc_for_sticky(frame.f_locals['__exception__'])
                if s:
                    print(s, file=self.stdout)

            elif '__return__' in frame.f_locals:
                rv = frame.f_locals['__return__']
                try:
                    s = repr(rv)
                except KeyboardInterrupt:
                    raise
                except:
                    s = '(unprintable return value)'

                s = ' return ' + s
                if self.config.highlight:
                    s = Color.set(self.config.line_number_color, s)
                print(s, file=self.stdout)

    def _format_exc_for_sticky(self, exc):
        if len(exc) != 2:
            return "pdbpp: got unexpected __exception__: %r" % (exc,)

        exc_type, exc_value = exc
        s = ''
        try:
            try:
                s = exc_type.__name__
            except AttributeError:
                s = str(exc_type)
            if exc_value is not None:
                s += ': '
                s += str(exc_value)
        except KeyboardInterrupt:
            raise
        except Exception as exc:
            try:
                s += '(unprintable exception: %r)' % (exc,)
            except:
                s += '(unprintable exception)'

        if self.config.highlight:
            s = Color.set(self.config.line_number_color, s)

        return s

    def do_sticky(self, arg):
        """
        sticky [start end]

        Toggle sticky mode. When in sticky mode, it clear the screen
        and longlist the current functions, making the source
        appearing always in the same position. Useful to follow the
        flow control of a function when doing step-by-step execution.

        If ``start`` and ``end`` are given, sticky mode is enabled and
        only lines within that range (extremes included) will be
        displayed.
        """
        if arg:
            try:
                start, end = map(int, arg.split())
            except ValueError:
                print('** Error when parsing argument: %s **' % arg,
                      file=self.stdout)
                return
            self.sticky = True
            self.sticky_ranges[self.curframe] = start, end+1
        else:
            self.sticky = not self.sticky
            self.sticky_range = None
        self._print_if_sticky()

    def print_stack_trace(self):
        try:
            for frame_index, frame_lineno in enumerate(self.stack):
                self.print_stack_entry(frame_lineno, frame_index=frame_index)
        except KeyboardInterrupt:
            pass

    def print_stack_entry(
        self, frame_lineno, prompt_prefix=pdb.line_prefix, frame_index=None
    ):
        frame, lineno = frame_lineno
        if frame is self.curframe:
            marker = "> "
        else:
            marker = "  "

        frame_prefix_width = len(str(len(self.stack)))
        if frame_index is None:
            frame_index = self.curindex
            fmt = "{frame_prefix}{marker}"
            lprefix = prompt_prefix  # "\n ->" by default
        else:
            # via/for stack trace
            fmt = "{marker}{frame_prefix}"
            lprefix = "\n     " + (" " * frame_prefix_width)

        # Format stack index (keeping same width across stack).
        frame_prefix = ("[%%%dd] " % frame_prefix_width) % frame_index

        marker_frameno = fmt.format(marker=marker, frame_prefix=frame_prefix)
        print(marker_frameno, file=self.stdout, end="")

        print(self.format_stack_entry(frame_lineno, lprefix), file=self.stdout)

    def print_current_stack_entry(self):
        if self.sticky:
            self._print_if_sticky()
        else:
            self.print_stack_entry(self.stack[self.curindex])

    def user_exception(self, frame, exc_info):
        self._skip_sticky = True
        return super(Pdb, self).user_exception(frame, exc_info)

    def preloop(self):
        if getattr(self, "_skip_sticky", False):
            del self._skip_sticky
        else:
            self._print_if_sticky()

        display_list = self._get_display_list()
        for expr, oldvalue in display_list.items():
            newvalue = self._getval_or_undefined(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 or newvalue != oldvalue:
                display_list[expr] = newvalue
                print('%s: %r --> %r' % (expr, oldvalue, newvalue),
                      file=self.stdout)

    def _get_position_of_arg(self, arg):
        try:
            obj = self._getval(arg)
        except:
            return None, None, None
        if isinstance(obj, str):
            return obj, 1, None
        try:
            filename = inspect.getabsfile(obj)
            lines, lineno = inspect.getsourcelines(obj)
        except (IOError, TypeError) as e:
            print('** Error: %s **' % e, file=self.stdout)
            return None, None, None
        return filename, lineno, lines

    def do_source(self, arg):
        _, lineno, lines = self._get_position_of_arg(arg)
        if lineno is None:
            return
        self._print_lines_pdbpp(lines, lineno, print_markers=False)

    def do_frame(self, arg):
        """f(rame) [index]
        Go to frame.
        Without argument, display current frame.
        """
        if not arg:
            # Just display the frame, without handling sticky.
            self.print_stack_entry(self.stack[self.curindex])
            return

        try:
            arg = int(arg)
        except (ValueError, TypeError):
            print(
                '*** Expected a number, got "{0}"'.format(arg), file=self.stdout)
            return
        if arg < 0 or arg >= len(self.stack):
            print('*** Out of range', file=self.stdout)
        else:
            self.curindex = arg
            self.curframe = self.stack[self.curindex][0]
            self.curframe_locals = self.curframe.f_locals
            self.print_current_stack_entry()
            self.lineno = None
    do_f = do_frame

    def do_up(self, arg='1'):
        arg = '1' if arg == '' else arg
        try:
            arg = int(arg)
        except (ValueError, TypeError):
            print(
                '*** Expected a number, got "{0}"'.format(arg), file=self.stdout)
            return
        if self.curindex - arg < 0:
            print('*** Oldest frame', file=self.stdout)
        else:
            self.curindex = self.curindex - arg
            self.curframe = self.stack[self.curindex][0]
            self.curframe_locals = self.curframe.f_locals
            self.print_current_stack_entry()
            self.lineno = None
    do_up.__doc__ = pdb.Pdb.do_up.__doc__
    do_u = do_up

    def do_down(self, arg='1'):
        arg = '1' if arg == '' else arg
        try:
            arg = int(arg)
        except (ValueError, TypeError):
            print(
                '*** Expected a number, got "{0}"'.format(arg), file=self.stdout)
            return
        if self.curindex + arg >= len(self.stack):
            print('*** Newest frame', file=self.stdout)
        else:
            self.curindex = self.curindex + arg
            self.curframe = self.stack[self.curindex][0]
            self.curframe_locals = self.curframe.f_locals
            self.print_current_stack_entry()
            self.lineno = None
    do_down.__doc__ = pdb.Pdb.do_down.__doc__
    do_d = do_down

    @staticmethod
    def get_terminal_size():
        fallback = (80, 24)
        try:
            from shutil import get_terminal_size
        except ImportError:
            try:
                import termios
                import fcntl
                import struct
                call = fcntl.ioctl(0, termios.TIOCGWINSZ, "\x00"*8)
                height, width = struct.unpack("hhhh", call)[:2]
            except (SystemExit, KeyboardInterrupt):
                raise
            except:
                width = int(os.environ.get('COLUMNS', fallback[0]))
                height = int(os.environ.get('COLUMNS', fallback[1]))
            # Work around above returning width, height = 0, 0 in Emacs
            width = width if width != 0 else fallback[0]
            height = height if height != 0 else fallback[1]
            return width, height
        else:
            return get_terminal_size(fallback)

    def _open_editor(self, editcmd):
        """Extra method to allow for easy override in tests."""
        subprocess.Popen(editcmd, shell=True).communicate()

    def _get_current_position(self):
        frame = self.curframe
        lineno = frame.f_lineno
        filename = os.path.abspath(frame.f_code.co_filename)
        return filename, lineno

    def _format_editcmd(self, editor, filename, lineno):
        try:
            from shutil import quote
        except ImportError:
            from pipes import quote

        filename = quote(filename)

        if "{filename}" in editor:
            return editor.format(filename=filename, lineno=lineno)

        if "%s" not in editor:
            # backward compatibility.
            return "%s +%d %s" % (editor, lineno, filename)

        # Replace %s with filename, %d with lineno; %% becomes %.
        return editor.replace("%%", "%").replace("%s", filename).replace(
            "%d", str(lineno))

    def _get_editor_cmd(self, filename, lineno):
        editor = self.config.editor
        if editor is None:
            try:
                editor = os.environ["EDITOR"]
            except KeyError:
                try:
                    from shutil import which
                except ImportError:
                    from distutils.spawn import find_executable as which
                editor = which("vim")
                if editor is None:
                    editor = which("vi")
            if not editor:
                raise RuntimeError("Could not detect editor. Configure it or set $EDITOR.")  # noqa: E501
        return self._format_editcmd(editor, filename, lineno)

    def do_edit(self, arg):
        "Open an editor visiting the current file at the current line"
        if arg == '':
            filename, lineno = self._get_current_position()
        else:
            filename, lineno, _ = self._get_position_of_arg(arg)
            if filename is None:
                return
        # this case handles code generated with py.code.Source()
        # filename is something like '<0-codegen foo.py:18>'
        match = re.match(r'.*<\d+-codegen (.*):(\d+)>', filename)
        if match:
            filename = match.group(1)
            lineno = int(match.group(2))

        try:
            self._open_editor(self._get_editor_cmd(filename, lineno))
        except Exception as exc:
            self.error(exc)

    do_ed = do_edit

    def _get_history(self):
        return [s for s in self.history if not side_effects_free.match(s)]

    def _get_history_text(self):
        import linecache
        line = linecache.getline(self.start_filename, self.start_lineno)
        nspaces = len(line) - len(line.lstrip())
        indent = ' ' * nspaces
        history = [indent + s for s in self._get_history()]
        return '\n'.join(history) + '\n'

    def _open_stdin_paste(self, stdin_paste, lineno, filename, text):
        proc = subprocess.Popen([stdin_paste, '+%d' % lineno, filename],
                                stdin=subprocess.PIPE)
        proc.stdin.write(text)
        proc.stdin.close()

    def _put(self, text):
        stdin_paste = self.config.stdin_paste
        if stdin_paste is None:
            print('** Error: the "stdin_paste" option is not configured **',
                  file=self.stdout)
        filename = self.start_filename
        lineno = self.start_lineno
        self._open_stdin_paste(stdin_paste, lineno, filename, text)

    def do_put(self, arg):
        text = self._get_history_text()
        self._put(text)

    def do_paste(self, arg):
        arg = arg.strip()
        old_stdout = self.stdout
        self.stdout = StringIO()
        self.onecmd(arg)
        text = self.stdout.getvalue()
        self.stdout = old_stdout
        sys.stdout.write(text)
        self._put(text)

    def set_trace(self, frame=None):
        """Remember starting frame.

        This is used with pytest, which does not use pdb.set_trace().
        """
        if getattr(local, "_pdbpp_completing", False):
            # Handle set_trace being called during completion, e.g. with
            # fancycompleter's attr_matches.
            return
        if self.disabled:
            return

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

        self.start_filename = frame.f_code.co_filename
        self.start_lineno = frame.f_lineno

        return super(Pdb, self).set_trace(frame)

    def is_skipped_module(self, module_name):
        """Backport for https://bugs.python.org/issue36130.

        Fixed in Python 3.8+.
        """
        if module_name is None:
            return False
        return super(Pdb, self).is_skipped_module(module_name)

    if not hasattr(pdb.Pdb, 'message'):  # For py27.

        def message(self, msg):
            print(msg, file=self.stdout)

    def error(self, msg):
        """Override/enhance default error method to display tracebacks."""
        print("***", msg, file=self.stdout)

        if not self.config.show_traceback_on_error:
            return

        etype, evalue, tb = sys.exc_info()
        if tb and tb.tb_frame.f_code.co_name == "default":
            tb = tb.tb_next
            if tb and tb.tb_frame.f_code.co_filename == "<stdin>":
                tb = tb.tb_next
                if tb:  # only display with actual traceback.
                    self._remove_bdb_context(evalue)
                    tb_limit = self.config.show_traceback_on_error_limit
                    fmt_exc = traceback.format_exception(
                        etype, evalue, tb, limit=tb_limit
                    )

                    # Remove last line (exception string again).
                    if len(fmt_exc) > 1 and fmt_exc[-1][0] != " ":
                        fmt_exc.pop()

                    print("".join(fmt_exc).rstrip(), file=self.stdout)

    @staticmethod
    def _remove_bdb_context(evalue):
        """Remove exception context from Pdb from the exception.

        E.g. "AttributeError: 'Pdb' object has no attribute 'do_foo'",
        when trying to look up commands (bpo-36494).
        """
        removed_bdb_context = evalue
        while removed_bdb_context.__context__:
            ctx = removed_bdb_context.__context__
            if (
                isinstance(ctx, AttributeError)
                and ctx.__traceback__.tb_frame.f_code.co_name == "onecmd"
            ):
                removed_bdb_context.__context__ = None
                break
            removed_bdb_context = removed_bdb_context.__context__


# simplified interface

if hasattr(pdb, 'Restart'):
    Restart = pdb.Restart

if hasattr(pdb, '_usage'):
    _usage = pdb._usage

# copy some functions from pdb.py, but rebind the global dictionary
for name in 'run runeval runctx runcall pm main set_trace'.split():
    func = getattr(pdb, name)
    globals()[name] = rebind_globals(func, globals())
del name, func


def post_mortem(t=None, Pdb=Pdb):
    if t is None:
        t = sys.exc_info()[2]
        assert t is not None, "post_mortem outside of exception context"

    p = Pdb()
    p.reset()
    p.interaction(None, t)


def cleanup():
    local.GLOBAL_PDB = None
    local._pdbpp_completing = False

# pdb++ specific interface


def xpm(Pdb=Pdb):
    """
    To be used inside an except clause, enter a post-mortem pdb
    related to the just catched exception.
    """
    info = sys.exc_info()
    print(traceback.format_exc())
    post_mortem(info[2], Pdb)


def enable():
    global set_trace
    set_trace = enable.set_trace
    if local.GLOBAL_PDB:
        local.GLOBAL_PDB.disabled = False


enable.set_trace = set_trace


def disable():
    global set_trace
    set_trace = disable.set_trace
    if local.GLOBAL_PDB:
        local.GLOBAL_PDB.disabled = True


disable.set_trace = lambda frame=None, Pdb=Pdb: None


def set_tracex():
    print('PDB!')


set_tracex._dont_inline_ = True

_HIDE_FRAME = object()


def hideframe(func):
    c = func.__code__
    if sys.version_info < (3, ):
        c = types.CodeType(
            c.co_argcount, c.co_nlocals, c.co_stacksize,
            c.co_flags, c.co_code,
            c.co_consts + (_HIDE_FRAME,),
            c.co_names, c.co_varnames, c.co_filename,
            c.co_name, c.co_firstlineno, c.co_lnotab,
            c.co_freevars, c.co_cellvars)
    else:
        # Python 3 takes an additional arg -- kwonlyargcount
        # typically set to 0
        c = types.CodeType(
            c.co_argcount, 0, c.co_nlocals, c.co_stacksize,
            c.co_flags, c.co_code,
            c.co_consts + (_HIDE_FRAME,),
            c.co_names, c.co_varnames, c.co_filename,
            c.co_name, c.co_firstlineno, c.co_lnotab,
            c.co_freevars, c.co_cellvars)
    func.__code__ = c
    return func


def always(obj, value):
    return True


def break_on_setattr(attrname, condition=always, Pdb=Pdb):
    def decorator(cls):
        old___setattr__ = cls.__setattr__

        @hideframe
        def __setattr__(self, attr, value):
            if attr == attrname and condition(self, value):
                frame = sys._getframe().f_back
                pdb_ = Pdb()
                pdb_.set_trace(frame)
                pdb_.stopframe = frame
                pdb_.interaction(frame, None)
            old___setattr__(self, attr, value)
        cls.__setattr__ = __setattr__
        return cls
    return decorator


if __name__ == '__main__':
    import pdb
    pdb.main()