bdb.py

"""Debugger basics"""

import fnmatch
import sys
import os

__all__ = ["BdbQuit", "Bdb", "Breakpoint"]

class BdbQuit(Exception):
    """Exception to give up completely."""


class Bdb:
    """Generic Python debugger base class.

    This class takes care of details of the trace facility;
    a derived class should implement user interaction.
    The standard debugger class (pdb.Pdb) is an example.
    """

    def __init__(self, skip=None):
        self.skip = set(skip) if skip else None
        self.breaks = {}
        self.fncache = {}
        self.frame_returning = None

    def canonic(self, filename):
        if filename == "<" + filename[1:-1] + ">":
            return filename
        canonic = self.fncache.get(filename)
        if not canonic:
            canonic = os.path.abspath(filename)
            canonic = os.path.normcase(canonic)
            self.fncache[filename] = canonic
        return canonic

    def reset(self):
        import linecache
        linecache.checkcache()
        self.botframe = None
        self._set_stopinfo(None, None)

    def trace_dispatch(self, frame, event, arg):
        if self.quitting:
            return # None
        if event == 'line':
            return self.dispatch_line(frame)
        if event == 'call':
            return self.dispatch_call(frame, arg)
        if event == 'return':
            return self.dispatch_return(frame, arg)
        if event == 'exception':
            return self.dispatch_exception(frame, arg)
        if event == 'c_call':
            return self.trace_dispatch
        if event == 'c_exception':
            return self.trace_dispatch
        if event == 'c_return':
            return self.trace_dispatch
        print('bdb.Bdb.dispatch: unknown debugging event:', repr(event))
        return self.trace_dispatch

    def dispatch_line(self, frame):
        if self.stop_here(frame) or self.break_here(frame):
            self.user_line(frame)
            if self.quitting: raise BdbQuit
        return self.trace_dispatch

    def dispatch_call(self, frame, arg):
        # XXX 'arg' is no longer used
        if self.botframe is None:
            # First call of dispatch since reset()
            self.botframe = frame.f_back # (CT) Note that this may also be None!
            return self.trace_dispatch
        if not (self.stop_here(frame) or self.break_anywhere(frame)):
            # No need to trace this function
            return # None
        self.user_call(frame, arg)
        if self.quitting: raise BdbQuit
        return self.trace_dispatch

    def dispatch_return(self, frame, arg):
        if self.stop_here(frame) or frame == self.returnframe:
            try:
                self.frame_returning = frame
                self.user_return(frame, arg)
            finally:
                self.frame_returning = None
            if self.quitting: raise BdbQuit
        return self.trace_dispatch

    def dispatch_exception(self, frame, arg):
        if self.stop_here(frame):
            self.user_exception(frame, arg)
            if self.quitting: raise BdbQuit
        return self.trace_dispatch

    # Normally derived classes don't override the following
    # methods, but they may if they want to redefine the
    # definition of stopping and breakpoints.

    def is_skipped_module(self, module_name):
        for pattern in self.skip:
            if fnmatch.fnmatch(module_name, pattern):
                return True
        return False

    def stop_here(self, frame):
        # (CT) stopframe may now also be None, see dispatch_call.
        # (CT) the former test for None is therefore removed from here.
        if self.skip and \
               self.is_skipped_module(frame.f_globals.get('__name__')):
            return False
        if frame is self.stopframe:
            if self.stoplineno == -1:
                return False
            return frame.f_lineno >= self.stoplineno
        while frame is not None and frame is not self.stopframe:
            if frame is self.botframe:
                return True
            frame = frame.f_back
        return False

    def break_here(self, frame):
        filename = self.canonic(frame.f_code.co_filename)
        if filename not in self.breaks:
            return False
        lineno = frame.f_lineno
        if lineno not in self.breaks[filename]:
            # The line itself has no breakpoint, but maybe the line is the
            # first line of a function with breakpoint set by function name.
            lineno = frame.f_code.co_firstlineno
            if lineno not in self.breaks[filename]:
                return False

        # flag says ok to delete temp. bp
        (bp, flag) = effective(filename, lineno, frame)
        if bp:
            self.currentbp = bp.number
            if (flag and bp.temporary):
                self.do_clear(str(bp.number))
            return True
        else:
            return False

    def do_clear(self, arg):
        raise NotImplementedError("subclass of bdb must implement do_clear()")

    def break_anywhere(self, frame):
        return self.canonic(frame.f_code.co_filename) in self.breaks

    # Derived classes should override the user_* methods
    # to gain control.

    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."""
        pass

    def user_line(self, frame):
        """This method is called when we stop or break at this line."""
        pass

    def user_return(self, frame, return_value):
        """This method is called when a return trap is set here."""
        pass

    def user_exception(self, frame, exc_info):
        """This method is called if an exception occurs,
        but only if we are to stop at or just below this level."""
        pass

    def _set_stopinfo(self, stopframe, returnframe, stoplineno=0):
        self.stopframe = stopframe
        self.returnframe = returnframe
        self.quitting = False
        # stoplineno >= 0 means: stop at line >= the stoplineno
        # stoplineno -1 means: don't stop at all
        self.stoplineno = stoplineno

    # Derived classes and clients can call the following methods
    # to affect the stepping state.

    def set_until(self, frame, lineno=None):
        """Stop when the line with the line no greater than the current one is
        reached or when returning from current frame"""
        # the name "until" is borrowed from gdb
        if lineno is None:
            lineno = frame.f_lineno + 1
        self._set_stopinfo(frame, frame, lineno)

    def set_step(self):
        """Stop after one line of code."""
        # Issue #13183: pdb skips frames after hitting a breakpoint and running
        # step commands.
        # Restore the trace function in the caller (that may not have been set
        # for performance reasons) when returning from the current frame.
        if self.frame_returning:
            caller_frame = self.frame_returning.f_back
            if caller_frame and not caller_frame.f_trace:
                caller_frame.f_trace = self.trace_dispatch
        self._set_stopinfo(None, None)

    def set_next(self, frame):
        """Stop on the next line in or below the given frame."""
        self._set_stopinfo(frame, None)

    def set_return(self, frame):
        """Stop when returning from the given frame."""
        self._set_stopinfo(frame.f_back, frame)

    def set_trace(self, frame=None):
        """Start debugging from `frame`.

        If frame is not specified, debugging starts from caller's frame.
        """
        if frame is None:
            frame = sys._getframe().f_back
        self.reset()
        while frame:
            frame.f_trace = self.trace_dispatch
            self.botframe = frame
            frame = frame.f_back
        self.set_step()
        sys.settrace(self.trace_dispatch)

    def set_continue(self):
        # Don't stop except at breakpoints or when finished
        self._set_stopinfo(self.botframe, None, -1)
        if not self.breaks:
            # no breakpoints; run without debugger overhead
            sys.settrace(None)
            frame = sys._getframe().f_back
            while frame and frame is not self.botframe:
                del frame.f_trace
                frame = frame.f_back

    def set_quit(self):
        self.stopframe = self.botframe
        self.returnframe = None
        self.quitting = True
        sys.settrace(None)

    # Derived classes and clients can call the following methods
    # to manipulate breakpoints.  These methods return an
    # error message is something went wrong, None if all is well.
    # Set_break prints out the breakpoint line and file:lineno.
    # Call self.get_*break*() to see the breakpoints or better
    # for bp in Breakpoint.bpbynumber: if bp: bp.bpprint().

    def set_break(self, filename, lineno, temporary=False, cond=None,
                  funcname=None):
        filename = self.canonic(filename)
        import linecache # Import as late as possible
        line = linecache.getline(filename, lineno)
        if not line:
            return 'Line %s:%d does not exist' % (filename, lineno)
        list = self.breaks.setdefault(filename, [])
        if lineno not in list:
            list.append(lineno)
        bp = Breakpoint(filename, lineno, temporary, cond, funcname)

    def _prune_breaks(self, filename, lineno):
        if (filename, lineno) not in Breakpoint.bplist:
            self.breaks[filename].remove(lineno)
        if not self.breaks[filename]:
            del self.breaks[filename]

    def clear_break(self, filename, lineno):
        filename = self.canonic(filename)
        if filename not in self.breaks:
            return 'There are no breakpoints in %s' % filename
        if lineno not in self.breaks[filename]:
            return 'There is no breakpoint at %s:%d' % (filename, lineno)
        # If there's only one bp in the list for that file,line
        # pair, then remove the breaks entry
        for bp in Breakpoint.bplist[filename, lineno][:]:
            bp.deleteMe()
        self._prune_breaks(filename, lineno)

    def clear_bpbynumber(self, arg):
        try:
            bp = self.get_bpbynumber(arg)
        except ValueError as err:
            return str(err)
        bp.deleteMe()
        self._prune_breaks(bp.file, bp.line)

    def clear_all_file_breaks(self, filename):
        filename = self.canonic(filename)
        if filename not in self.breaks:
            return 'There are no breakpoints in %s' % filename
        for line in self.breaks[filename]:
            blist = Breakpoint.bplist[filename, line]
            for bp in blist:
                bp.deleteMe()
        del self.breaks[filename]

    def clear_all_breaks(self):
        if not self.breaks:
            return 'There are no breakpoints'
        for bp in Breakpoint.bpbynumber:
            if bp:
                bp.deleteMe()
        self.breaks = {}

    def get_bpbynumber(self, arg):
        if not arg:
            raise ValueError('Breakpoint number expected')
        try:
            number = int(arg)
        except ValueError:
            raise ValueError('Non-numeric breakpoint number %s' % arg)
        try:
            bp = Breakpoint.bpbynumber[number]
        except IndexError:
            raise ValueError('Breakpoint number %d out of range' % number)
        if bp is None:
            raise ValueError('Breakpoint %d already deleted' % number)
        return bp

    def get_break(self, filename, lineno):
        filename = self.canonic(filename)
        return filename in self.breaks and \
            lineno in self.breaks[filename]

    def get_breaks(self, filename, lineno):
        filename = self.canonic(filename)
        return filename in self.breaks and \
            lineno in self.breaks[filename] and \
            Breakpoint.bplist[filename, lineno] or []

    def get_file_breaks(self, filename):
        filename = self.canonic(filename)
        if filename in self.breaks:
            return self.breaks[filename]
        else:
            return []

    def get_all_breaks(self):
        return self.breaks

    # Derived classes and clients can call the following method
    # to get a data structure representing a stack trace.

    def get_stack(self, f, t):
        stack = []
        if t and t.tb_frame is f:
            t = t.tb_next
        while f is not None:
            stack.append((f, f.f_lineno))
            if f is self.botframe:
                break
            f = f.f_back
        stack.reverse()
        i = max(0, len(stack) - 1)
        while t is not None:
            stack.append((t.tb_frame, t.tb_lineno))
            t = t.tb_next
        if f is None:
            i = max(0, len(stack) - 1)
        return stack, i

    def format_stack_entry(self, frame_lineno, lprefix=': '):
        import linecache, reprlib
        frame, lineno = frame_lineno
        filename = self.canonic(frame.f_code.co_filename)
        s = '%s(%r)' % (filename, lineno)
        if frame.f_code.co_name:
            s += frame.f_code.co_name
        else:
            s += "<lambda>"
        if '__args__' in frame.f_locals:
            args = frame.f_locals['__args__']
        else:
            args = None
        if args:
            s += reprlib.repr(args)
        else:
            s += '()'
        if '__return__' in frame.f_locals:
            rv = frame.f_locals['__return__']
            s += '->'
            s += reprlib.repr(rv)
        line = linecache.getline(filename, lineno, frame.f_globals)
        if line:
            s += lprefix + line.strip()
        return s

    # The following methods can be called by clients to use
    # a debugger to debug a statement or an expression.
    # Both can be given as a string, or a code object.

    def run(self, cmd, globals=None, locals=None):
        if globals is None:
            import __main__
            globals = __main__.__dict__
        if locals is None:
            locals = globals
        self.reset()
        if isinstance(cmd, str):
            cmd = compile(cmd, "<string>", "exec")
        sys.settrace(self.trace_dispatch)
        try:
            exec(cmd, globals, locals)
        except BdbQuit:
            pass
        finally:
            self.quitting = True
            sys.settrace(None)

    def runeval(self, expr, globals=None, locals=None):
        if globals is None:
            import __main__
            globals = __main__.__dict__
        if locals is None:
            locals = globals
        self.reset()
        sys.settrace(self.trace_dispatch)
        try:
            return eval(expr, globals, locals)
        except BdbQuit:
            pass
        finally:
            self.quitting = True
            sys.settrace(None)

    def runctx(self, cmd, globals, locals):
        # B/W compatibility
        self.run(cmd, globals, locals)

    # This method is more useful to debug a single function call.

    def runcall(self, func, *args, **kwds):
        self.reset()
        sys.settrace(self.trace_dispatch)
        res = None
        try:
            res = func(*args, **kwds)
        except BdbQuit:
            pass
        finally:
            self.quitting = True
            sys.settrace(None)
        return res


def set_trace():
    Bdb().set_trace()


class Breakpoint:
    """Breakpoint class.

    Implements temporary breakpoints, ignore counts, disabling and
    (re)-enabling, and conditionals.

    Breakpoints are indexed by number through bpbynumber and by
    the file,line tuple using bplist.  The former points to a
    single instance of class Breakpoint.  The latter points to a
    list of such instances since there may be more than one
    breakpoint per line.

    """

    # XXX Keeping state in the class is a mistake -- this means
    # you cannot have more than one active Bdb instance.

    next = 1        # Next bp to be assigned
    bplist = {}     # indexed by (file, lineno) tuple
    bpbynumber = [None] # Each entry is None or an instance of Bpt
                # index 0 is unused, except for marking an
                # effective break .... see effective()

    def __init__(self, file, line, temporary=False, cond=None, funcname=None):
        self.funcname = funcname
        # Needed if funcname is not None.
        self.func_first_executable_line = None
        self.file = file    # This better be in canonical form!
        self.line = line
        self.temporary = temporary
        self.cond = cond
        self.enabled = True
        self.ignore = 0
        self.hits = 0
        self.number = Breakpoint.next
        Breakpoint.next += 1
        # Build the two lists
        self.bpbynumber.append(self)
        if (file, line) in self.bplist:
            self.bplist[file, line].append(self)
        else:
            self.bplist[file, line] = [self]

    def deleteMe(self):
        index = (self.file, self.line)
        self.bpbynumber[self.number] = None   # No longer in list
        self.bplist[index].remove(self)
        if not self.bplist[index]:
            # No more bp for this f:l combo
            del self.bplist[index]

    def enable(self):
        self.enabled = True

    def disable(self):
        self.enabled = False

    def bpprint(self, out=None):
        if out is None:
            out = sys.stdout
        print(self.bpformat(), file=out)

    def bpformat(self):
        if self.temporary:
            disp = 'del  '
        else:
            disp = 'keep '
        if self.enabled:
            disp = disp + 'yes  '
        else:
            disp = disp + 'no   '
        ret = '%-4dbreakpoint   %s at %s:%d' % (self.number, disp,
                                                self.file, self.line)
        if self.cond:
            ret += '\n\tstop only if %s' % (self.cond,)
        if self.ignore:
            ret += '\n\tignore next %d hits' % (self.ignore,)
        if self.hits:
            if self.hits > 1:
                ss = 's'
            else:
                ss = ''
            ret += '\n\tbreakpoint already hit %d time%s' % (self.hits, ss)
        return ret

    def __str__(self):
        return 'breakpoint %s at %s:%s' % (self.number, self.file, self.line)

# -----------end of Breakpoint class----------

def checkfuncname(b, frame):
    """Check whether we should break here because of `b.funcname`."""
    if not b.funcname:
        # Breakpoint was set via line number.
        if b.line != frame.f_lineno:
            # Breakpoint was set at a line with a def statement and the function
            # defined is called: don't break.
            return False
        return True

    # Breakpoint set via function name.

    if frame.f_code.co_name != b.funcname:
        # It's not a function call, but rather execution of def statement.
        return False

    # We are in the right frame.
    if not b.func_first_executable_line:
        # The function is entered for the 1st time.
        b.func_first_executable_line = frame.f_lineno

    if  b.func_first_executable_line != frame.f_lineno:
        # But we are not at the first line number: don't break.
        return False
    return True

# Determines if there is an effective (active) breakpoint at this
# line of code.  Returns breakpoint number or 0 if none
def effective(file, line, frame):
    """Determine which breakpoint for this file:line is to be acted upon.

    Called only if we know there is a bpt at this
    location.  Returns breakpoint that was triggered and a flag
    that indicates if it is ok to delete a temporary bp.

    """
    possibles = Breakpoint.bplist[file, line]
    for b in possibles:
        if not b.enabled:
            continue
        if not checkfuncname(b, frame):
            continue
        # Count every hit when bp is enabled
        b.hits += 1
        if not b.cond:
            # If unconditional, and ignoring go on to next, else break
            if b.ignore > 0:
                b.ignore -= 1
                continue
            else:
                # breakpoint and marker that it's ok to delete if temporary
                return (b, True)
        else:
            # Conditional bp.
            # Ignore count applies only to those bpt hits where the
            # condition evaluates to true.
            try:
                val = eval(b.cond, frame.f_globals, frame.f_locals)
                if val:
                    if b.ignore > 0:
                        b.ignore -= 1
                        # continue
                    else:
                        return (b, True)
                # else:
                #   continue
            except:
                # if eval fails, most conservative thing is to stop on
                # breakpoint regardless of ignore count.  Don't delete
                # temporary, as another hint to user.
                return (b, False)
    return (None, None)


# -------------------- testing --------------------

class Tdb(Bdb):
    def user_call(self, frame, args):
        name = frame.f_code.co_name
        if not name: name = '???'
        print('+++ call', name, args)
    def user_line(self, frame):
        import linecache
        name = frame.f_code.co_name
        if not name: name = '???'
        fn = self.canonic(frame.f_code.co_filename)
        line = linecache.getline(fn, frame.f_lineno, frame.f_globals)
        print('+++', fn, frame.f_lineno, name, ':', line.strip())
    def user_return(self, frame, retval):
        print('+++ return', retval)
    def user_exception(self, frame, exc_stuff):
        print('+++ exception', exc_stuff)
        self.set_continue()

def foo(n):
    print('foo(', n, ')')
    x = bar(n*10)
    print('bar returned', x)

def bar(a):
    print('bar(', a, ')')
    return a/2

def test():
    t = Tdb()
    t.run('import bdb; bdb.foo(10)')