654 lines
23 KiB
Python
654 lines
23 KiB
Python
# -*- test-case-name: twisted.test.test_failure -*-
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# See also test suite twisted.test.test_pbfailure
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# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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"""
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Asynchronous-friendly error mechanism.
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See L{Failure}.
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"""
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from __future__ import division, absolute_import
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# System Imports
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import sys
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import linecache
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import inspect
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import opcode
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from inspect import getmro
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from twisted.python.compat import _PY3, NativeStringIO as StringIO
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from twisted.python import reflect
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count = 0
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traceupLength = 4
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class DefaultException(Exception):
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pass
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def format_frames(frames, write, detail="default"):
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"""Format and write frames.
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@param frames: is a list of frames as used by Failure.frames, with
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each frame being a list of
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(funcName, fileName, lineNumber, locals.items(), globals.items())
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@type frames: list
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@param write: this will be called with formatted strings.
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@type write: callable
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@param detail: Four detail levels are available:
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default, brief, verbose, and verbose-vars-not-captured.
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C{Failure.printDetailedTraceback} uses the latter when the caller asks
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for verbose, but no vars were captured, so that an explicit warning
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about the missing data is shown.
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@type detail: string
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"""
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if detail not in ('default', 'brief', 'verbose',
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'verbose-vars-not-captured'):
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raise ValueError(
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"Detail must be default, brief, verbose, or "
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"verbose-vars-not-captured. (not %r)" % (detail,))
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w = write
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if detail == "brief":
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for method, filename, lineno, localVars, globalVars in frames:
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w('%s:%s:%s\n' % (filename, lineno, method))
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elif detail == "default":
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for method, filename, lineno, localVars, globalVars in frames:
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w( ' File "%s", line %s, in %s\n' % (filename, lineno, method))
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w( ' %s\n' % linecache.getline(filename, lineno).strip())
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elif detail == "verbose-vars-not-captured":
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for method, filename, lineno, localVars, globalVars in frames:
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w("%s:%d: %s(...)\n" % (filename, lineno, method))
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w(' [Capture of Locals and Globals disabled (use captureVars=True)]\n')
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elif detail == "verbose":
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for method, filename, lineno, localVars, globalVars in frames:
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w("%s:%d: %s(...)\n" % (filename, lineno, method))
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w(' [ Locals ]\n')
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# Note: the repr(val) was (self.pickled and val) or repr(val)))
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for name, val in localVars:
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w(" %s : %s\n" % (name, repr(val)))
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w(' ( Globals )\n')
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for name, val in globalVars:
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w(" %s : %s\n" % (name, repr(val)))
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# slyphon: i have a need to check for this value in trial
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# so I made it a module-level constant
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EXCEPTION_CAUGHT_HERE = "--- <exception caught here> ---"
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class NoCurrentExceptionError(Exception):
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"""
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Raised when trying to create a Failure from the current interpreter
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exception state and there is no current exception state.
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"""
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class _Traceback(object):
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"""
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Fake traceback object which can be passed to functions in the standard
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library L{traceback} module.
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"""
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def __init__(self, frames):
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"""
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Construct a fake traceback object using a list of frames. Note that
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although frames generally include locals and globals, this information
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is not kept by this object, since locals and globals are not used in
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standard tracebacks.
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@param frames: [(methodname, filename, lineno, locals, globals), ...]
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"""
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assert len(frames) > 0, "Must pass some frames"
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head, frames = frames[0], frames[1:]
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name, filename, lineno, localz, globalz = head
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self.tb_frame = _Frame(name, filename)
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self.tb_lineno = lineno
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if len(frames) == 0:
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self.tb_next = None
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else:
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self.tb_next = _Traceback(frames)
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class _Frame(object):
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"""
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A fake frame object, used by L{_Traceback}.
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@ivar f_code: fake L{code<types.CodeType>} object
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@ivar f_globals: fake f_globals dictionary (usually empty)
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@ivar f_locals: fake f_locals dictionary (usually empty)
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"""
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def __init__(self, name, filename):
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"""
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@param name: method/function name for this frame.
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@type name: C{str}
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@param filename: filename for this frame.
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@type name: C{str}
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"""
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self.f_code = _Code(name, filename)
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self.f_globals = {}
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self.f_locals = {}
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class _Code(object):
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"""
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A fake code object, used by L{_Traceback} via L{_Frame}.
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"""
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def __init__(self, name, filename):
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self.co_name = name
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self.co_filename = filename
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class Failure:
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"""
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A basic abstraction for an error that has occurred.
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This is necessary because Python's built-in error mechanisms are
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inconvenient for asynchronous communication.
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The C{stack} and C{frame} attributes contain frames. Each frame is a tuple
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of (funcName, fileName, lineNumber, localsItems, globalsItems), where
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localsItems and globalsItems are the contents of
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C{locals().items()}/C{globals().items()} for that frame, or an empty tuple
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if those details were not captured.
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@ivar value: The exception instance responsible for this failure.
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@ivar type: The exception's class.
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@ivar stack: list of frames, innermost last, excluding C{Failure.__init__}.
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@ivar frames: list of frames, innermost first.
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"""
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pickled = 0
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stack = None
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# The opcode of "yield" in Python bytecode. We need this in _findFailure in
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# order to identify whether an exception was thrown by a
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# throwExceptionIntoGenerator.
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_yieldOpcode = chr(opcode.opmap["YIELD_VALUE"])
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def __init__(self, exc_value=None, exc_type=None, exc_tb=None,
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captureVars=False):
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"""
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Initialize me with an explanation of the error.
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By default, this will use the current C{exception}
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(L{sys.exc_info}()). However, if you want to specify a
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particular kind of failure, you can pass an exception as an
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argument.
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If no C{exc_value} is passed, then an "original" C{Failure} will
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be searched for. If the current exception handler that this
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C{Failure} is being constructed in is handling an exception
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raised by L{raiseException}, then this C{Failure} will act like
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the original C{Failure}.
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For C{exc_tb} only L{traceback} instances or C{None} are allowed.
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If C{None} is supplied for C{exc_value}, the value of C{exc_tb} is
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ignored, otherwise if C{exc_tb} is C{None}, it will be found from
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execution context (ie, L{sys.exc_info}).
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@param captureVars: if set, capture locals and globals of stack
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frames. This is pretty slow, and makes no difference unless you
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are going to use L{printDetailedTraceback}.
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"""
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global count
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count = count + 1
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self.count = count
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self.type = self.value = tb = None
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self.captureVars = captureVars
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if isinstance(exc_value, str) and exc_type is None:
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raise TypeError("Strings are not supported by Failure")
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stackOffset = 0
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if exc_value is None:
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exc_value = self._findFailure()
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if exc_value is None:
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self.type, self.value, tb = sys.exc_info()
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if self.type is None:
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raise NoCurrentExceptionError()
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stackOffset = 1
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elif exc_type is None:
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if isinstance(exc_value, Exception):
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self.type = exc_value.__class__
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else: #allow arbitrary objects.
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self.type = type(exc_value)
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self.value = exc_value
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else:
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self.type = exc_type
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self.value = exc_value
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if isinstance(self.value, Failure):
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self.__dict__ = self.value.__dict__
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return
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if tb is None:
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if exc_tb:
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tb = exc_tb
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elif _PY3:
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tb = self.value.__traceback__
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frames = self.frames = []
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stack = self.stack = []
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# added 2003-06-23 by Chris Armstrong. Yes, I actually have a
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# use case where I need this traceback object, and I've made
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# sure that it'll be cleaned up.
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self.tb = tb
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if tb:
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f = tb.tb_frame
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elif not isinstance(self.value, Failure):
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# we don't do frame introspection since it's expensive,
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# and if we were passed a plain exception with no
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# traceback, it's not useful anyway
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f = stackOffset = None
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while stackOffset and f:
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# This excludes this Failure.__init__ frame from the
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# stack, leaving it to start with our caller instead.
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f = f.f_back
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stackOffset -= 1
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# Keeps the *full* stack. Formerly in spread.pb.print_excFullStack:
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#
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# The need for this function arises from the fact that several
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# PB classes have the peculiar habit of discarding exceptions
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# with bareword "except:"s. This premature exception
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# catching means tracebacks generated here don't tend to show
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# what called upon the PB object.
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while f:
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if captureVars:
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localz = f.f_locals.copy()
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if f.f_locals is f.f_globals:
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globalz = {}
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else:
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globalz = f.f_globals.copy()
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for d in globalz, localz:
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if "__builtins__" in d:
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del d["__builtins__"]
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localz = localz.items()
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globalz = globalz.items()
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else:
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localz = globalz = ()
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stack.insert(0, (
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f.f_code.co_name,
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f.f_code.co_filename,
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f.f_lineno,
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localz,
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globalz,
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))
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f = f.f_back
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while tb is not None:
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f = tb.tb_frame
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if captureVars:
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localz = f.f_locals.copy()
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if f.f_locals is f.f_globals:
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globalz = {}
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else:
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globalz = f.f_globals.copy()
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for d in globalz, localz:
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if "__builtins__" in d:
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del d["__builtins__"]
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localz = list(localz.items())
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globalz = list(globalz.items())
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else:
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localz = globalz = ()
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frames.append((
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f.f_code.co_name,
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f.f_code.co_filename,
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tb.tb_lineno,
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localz,
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globalz,
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))
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tb = tb.tb_next
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if inspect.isclass(self.type) and issubclass(self.type, Exception):
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parentCs = getmro(self.type)
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self.parents = list(map(reflect.qual, parentCs))
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else:
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self.parents = [self.type]
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def trap(self, *errorTypes):
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"""Trap this failure if its type is in a predetermined list.
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This allows you to trap a Failure in an error callback. It will be
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automatically re-raised if it is not a type that you expect.
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The reason for having this particular API is because it's very useful
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in Deferred errback chains::
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def _ebFoo(self, failure):
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r = failure.trap(Spam, Eggs)
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print 'The Failure is due to either Spam or Eggs!'
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if r == Spam:
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print 'Spam did it!'
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elif r == Eggs:
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print 'Eggs did it!'
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If the failure is not a Spam or an Eggs, then the Failure will be
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'passed on' to the next errback. In Python 2 the Failure will be
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raised; in Python 3 the underlying exception will be re-raised.
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@type errorTypes: L{Exception}
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"""
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error = self.check(*errorTypes)
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if not error:
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if _PY3:
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self.raiseException()
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else:
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raise self
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return error
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def check(self, *errorTypes):
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"""Check if this failure's type is in a predetermined list.
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@type errorTypes: list of L{Exception} classes or
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fully-qualified class names.
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@returns: the matching L{Exception} type, or None if no match.
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"""
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for error in errorTypes:
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err = error
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if inspect.isclass(error) and issubclass(error, Exception):
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err = reflect.qual(error)
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if err in self.parents:
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return error
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return None
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# It would be nice to use twisted.python.compat.reraise, but that breaks
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# the stack exploration in _findFailure; possibly this can be fixed in
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# #5931.
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if _PY3:
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def raiseException(self):
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raise self.value.with_traceback(self.tb)
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else:
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exec("""def raiseException(self):
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raise self.type, self.value, self.tb""")
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raiseException.__doc__ = (
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"""
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raise the original exception, preserving traceback
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information if available.
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""")
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def throwExceptionIntoGenerator(self, g):
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"""
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Throw the original exception into the given generator,
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preserving traceback information if available.
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@return: The next value yielded from the generator.
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@raise StopIteration: If there are no more values in the generator.
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@raise anything else: Anything that the generator raises.
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"""
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return g.throw(self.type, self.value, self.tb)
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def _findFailure(cls):
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"""
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Find the failure that represents the exception currently in context.
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"""
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tb = sys.exc_info()[-1]
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if not tb:
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return
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secondLastTb = None
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lastTb = tb
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while lastTb.tb_next:
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secondLastTb = lastTb
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lastTb = lastTb.tb_next
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lastFrame = lastTb.tb_frame
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# NOTE: f_locals.get('self') is used rather than
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# f_locals['self'] because psyco frames do not contain
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# anything in their locals() dicts. psyco makes debugging
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# difficult anyhow, so losing the Failure objects (and thus
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# the tracebacks) here when it is used is not that big a deal.
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# handle raiseException-originated exceptions
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if lastFrame.f_code is cls.raiseException.__code__:
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return lastFrame.f_locals.get('self')
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# handle throwExceptionIntoGenerator-originated exceptions
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# this is tricky, and differs if the exception was caught
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# inside the generator, or above it:
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# it is only really originating from
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# throwExceptionIntoGenerator if the bottom of the traceback
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# is a yield.
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# Pyrex and Cython extensions create traceback frames
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# with no co_code, but they can't yield so we know it's okay to just return here.
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if ((not lastFrame.f_code.co_code) or
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lastFrame.f_code.co_code[lastTb.tb_lasti] != cls._yieldOpcode):
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return
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# if the exception was caught above the generator.throw
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# (outside the generator), it will appear in the tb (as the
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# second last item):
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if secondLastTb:
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frame = secondLastTb.tb_frame
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if frame.f_code is cls.throwExceptionIntoGenerator.__code__:
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return frame.f_locals.get('self')
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# if the exception was caught below the generator.throw
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# (inside the generator), it will appear in the frames' linked
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# list, above the top-level traceback item (which must be the
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# generator frame itself, thus its caller is
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# throwExceptionIntoGenerator).
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frame = tb.tb_frame.f_back
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if frame and frame.f_code is cls.throwExceptionIntoGenerator.__code__:
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return frame.f_locals.get('self')
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_findFailure = classmethod(_findFailure)
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def __repr__(self):
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return "<%s %s>" % (self.__class__, self.type)
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def __str__(self):
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return "[Failure instance: %s]" % self.getBriefTraceback()
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def __getstate__(self):
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"""Avoid pickling objects in the traceback.
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"""
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if self.pickled:
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return self.__dict__
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c = self.__dict__.copy()
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c['frames'] = [
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[
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v[0], v[1], v[2],
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_safeReprVars(v[3]),
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_safeReprVars(v[4]),
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] for v in self.frames
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]
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# added 2003-06-23. See comment above in __init__
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c['tb'] = None
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if self.stack is not None:
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# XXX: This is a band-aid. I can't figure out where these
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# (failure.stack is None) instances are coming from.
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c['stack'] = [
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[
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v[0], v[1], v[2],
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_safeReprVars(v[3]),
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_safeReprVars(v[4]),
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] for v in self.stack
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]
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c['pickled'] = 1
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return c
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def cleanFailure(self):
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"""
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Remove references to other objects, replacing them with strings.
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On Python 3, this will also set the C{__traceback__} attribute of the
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exception instance to C{None}.
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"""
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self.__dict__ = self.__getstate__()
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if _PY3:
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self.value.__traceback__ = None
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def getTracebackObject(self):
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"""
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Get an object that represents this Failure's stack that can be passed
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to traceback.extract_tb.
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If the original traceback object is still present, return that. If this
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traceback object has been lost but we still have the information,
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return a fake traceback object (see L{_Traceback}). If there is no
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traceback information at all, return None.
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"""
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if self.tb is not None:
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return self.tb
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elif len(self.frames) > 0:
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return _Traceback(self.frames)
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else:
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return None
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def getErrorMessage(self):
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"""Get a string of the exception which caused this Failure."""
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if isinstance(self.value, Failure):
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return self.value.getErrorMessage()
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return reflect.safe_str(self.value)
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def getBriefTraceback(self):
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io = StringIO()
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self.printBriefTraceback(file=io)
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return io.getvalue()
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def getTraceback(self, elideFrameworkCode=0, detail='default'):
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io = StringIO()
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self.printTraceback(file=io, elideFrameworkCode=elideFrameworkCode, detail=detail)
|
|
return io.getvalue()
|
|
|
|
|
|
def printTraceback(self, file=None, elideFrameworkCode=False, detail='default'):
|
|
"""
|
|
Emulate Python's standard error reporting mechanism.
|
|
|
|
@param file: If specified, a file-like object to which to write the
|
|
traceback.
|
|
|
|
@param elideFrameworkCode: A flag indicating whether to attempt to
|
|
remove uninteresting frames from within Twisted itself from the
|
|
output.
|
|
|
|
@param detail: A string indicating how much information to include
|
|
in the traceback. Must be one of C{'brief'}, C{'default'}, or
|
|
C{'verbose'}.
|
|
"""
|
|
if file is None:
|
|
from twisted.python import log
|
|
file = log.logerr
|
|
w = file.write
|
|
|
|
if detail == 'verbose' and not self.captureVars:
|
|
# We don't have any locals or globals, so rather than show them as
|
|
# empty make the output explicitly say that we don't have them at
|
|
# all.
|
|
formatDetail = 'verbose-vars-not-captured'
|
|
else:
|
|
formatDetail = detail
|
|
|
|
# Preamble
|
|
if detail == 'verbose':
|
|
w( '*--- Failure #%d%s---\n' %
|
|
(self.count,
|
|
(self.pickled and ' (pickled) ') or ' '))
|
|
elif detail == 'brief':
|
|
if self.frames:
|
|
hasFrames = 'Traceback'
|
|
else:
|
|
hasFrames = 'Traceback (failure with no frames)'
|
|
w("%s: %s: %s\n" % (
|
|
hasFrames,
|
|
reflect.safe_str(self.type),
|
|
reflect.safe_str(self.value)))
|
|
else:
|
|
w( 'Traceback (most recent call last):\n')
|
|
|
|
# Frames, formatted in appropriate style
|
|
if self.frames:
|
|
if not elideFrameworkCode:
|
|
format_frames(self.stack[-traceupLength:], w, formatDetail)
|
|
w("%s\n" % (EXCEPTION_CAUGHT_HERE,))
|
|
format_frames(self.frames, w, formatDetail)
|
|
elif not detail == 'brief':
|
|
# Yeah, it's not really a traceback, despite looking like one...
|
|
w("Failure: ")
|
|
|
|
# postamble, if any
|
|
if not detail == 'brief':
|
|
w("%s: %s\n" % (reflect.qual(self.type),
|
|
reflect.safe_str(self.value)))
|
|
|
|
# chaining
|
|
if isinstance(self.value, Failure):
|
|
# TODO: indentation for chained failures?
|
|
file.write(" (chained Failure)\n")
|
|
self.value.printTraceback(file, elideFrameworkCode, detail)
|
|
if detail == 'verbose':
|
|
w('*--- End of Failure #%d ---\n' % self.count)
|
|
|
|
|
|
def printBriefTraceback(self, file=None, elideFrameworkCode=0):
|
|
"""Print a traceback as densely as possible.
|
|
"""
|
|
self.printTraceback(file, elideFrameworkCode, detail='brief')
|
|
|
|
def printDetailedTraceback(self, file=None, elideFrameworkCode=0):
|
|
"""Print a traceback with detailed locals and globals information.
|
|
"""
|
|
self.printTraceback(file, elideFrameworkCode, detail='verbose')
|
|
|
|
|
|
def _safeReprVars(varsDictItems):
|
|
"""
|
|
Convert a list of (name, object) pairs into (name, repr) pairs.
|
|
|
|
L{twisted.python.reflect.safe_repr} is used to generate the repr, so no
|
|
exceptions will be raised by faulty C{__repr__} methods.
|
|
|
|
@param varsDictItems: a sequence of (name, value) pairs as returned by e.g.
|
|
C{locals().items()}.
|
|
@returns: a sequence of (name, repr) pairs.
|
|
"""
|
|
return [(name, reflect.safe_repr(obj)) for (name, obj) in varsDictItems]
|
|
|
|
|
|
# slyphon: make post-morteming exceptions tweakable
|
|
|
|
DO_POST_MORTEM = True
|
|
|
|
def _debuginit(self, exc_value=None, exc_type=None, exc_tb=None,
|
|
captureVars=False,
|
|
Failure__init__=Failure.__init__):
|
|
"""
|
|
Initialize failure object, possibly spawning pdb.
|
|
"""
|
|
if (exc_value, exc_type, exc_tb) == (None, None, None):
|
|
exc = sys.exc_info()
|
|
if not exc[0] == self.__class__ and DO_POST_MORTEM:
|
|
try:
|
|
strrepr = str(exc[1])
|
|
except:
|
|
strrepr = "broken str"
|
|
print("Jumping into debugger for post-mortem of exception '%s':" % (strrepr,))
|
|
import pdb
|
|
pdb.post_mortem(exc[2])
|
|
Failure__init__(self, exc_value, exc_type, exc_tb, captureVars)
|
|
|
|
|
|
def startDebugMode():
|
|
"""Enable debug hooks for Failures."""
|
|
Failure.__init__ = _debuginit
|