713 lines
22 KiB
Python
713 lines
22 KiB
Python
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# -*- 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 annotations
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# System Imports
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import builtins
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import copy
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import inspect
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import linecache
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import sys
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from functools import partial
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from inspect import getmro
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from io import StringIO
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from typing import Callable, NoReturn, TypeVar
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from incremental import Version
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from twisted.python import reflect
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from twisted.python.deprecate import deprecatedProperty
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_T_Callable = TypeVar("_T_Callable", bound=Callable[..., object])
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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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"""
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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", "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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)
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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(f"{filename}:{lineno}:{method}\n")
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elif detail == "default":
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for method, filename, lineno, localVars, globalVars in frames:
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w(f' File "{filename}", line {lineno}, in {method}\n')
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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(f" {name} : {repr(val)}\n")
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w(" ( Globals )\n")
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for name, val in globalVars:
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w(f" {name} : {repr(val)}\n")
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# Unused, here for backwards compatibility.
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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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def _Traceback(tbFrames):
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"""
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Construct a fake traceback object using a list of frames.
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It should have the same API as stdlib to allow interaction with
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other tools.
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@param tbFrames: [(methodname, filename, lineno, locals, globals), ...]
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"""
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assert len(tbFrames) > 0, "Must pass some frames"
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# We deliberately avoid using recursion here, as the frames list may be
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# long.
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stack = None
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# 'tbFrames' is a list of frames from the point the exception was caught,
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# down to where it was thrown, with the oldest at the start. Add these to
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# the linked list of _Frames, but also wrap each one with a _Traceback
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# frame which is linked in the opposite direction (towards the newest
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# frame).
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stack = _Frame(tbFrames[0], stack)
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firstTb = tb = _TracebackFrame(stack)
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for sf in tbFrames[1:]:
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stack = _Frame(sf, stack)
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tb.tb_next = _TracebackFrame(stack)
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tb = tb.tb_next
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# Return the first _TracebackFrame.
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return firstTb
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# The set of attributes for _TracebackFrame, _Frame and _Code were taken from
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# https://docs.python.org/3.11/library/inspect.html Other Pythons may have a
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# few more attributes that should be added if needed.
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class _TracebackFrame:
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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, frame):
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"""
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@param frame: _Frame object
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"""
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self.tb_frame = frame
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self.tb_lineno = frame.f_lineno
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self.tb_lasti = frame.f_lasti
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self.tb_next = None
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class _Frame:
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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_lineno: line number
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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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@ivar f_back: previous stack frame (towards the caller)
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"""
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def __init__(self, frameinfo, back):
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"""
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@param frameinfo: (methodname, filename, lineno, locals, globals)
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@param back: previous (older) stack frame
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@type back: C{frame}
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"""
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name, filename, lineno, localz, globalz = frameinfo
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self.f_code = _Code(name, filename)
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self.f_lineno = lineno
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self.f_globals = dict(globalz or {})
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self.f_locals = dict(localz or {})
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self.f_back = back
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self.f_lasti = 0
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self.f_builtins = vars(builtins).copy()
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self.f_trace = None
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class _Code:
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"""
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A fake code object, used by L{_Traceback} via L{_Frame}.
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It is intended to have the same API as the stdlib code type to allow
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interoperation with other tools based on that interface.
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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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self.co_lnotab = b""
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self.co_firstlineno = 0
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self.co_argcount = 0
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self.co_varnames = []
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self.co_code = b""
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self.co_cellvars = ()
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self.co_consts = ()
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self.co_flags = 0
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self.co_freevars = ()
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self.co_posonlyargcount = 0
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self.co_kwonlyargcount = 0
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self.co_names = ()
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self.co_nlocals = 0
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self.co_stacksize = 0
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def co_positions(self):
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return ((None, None, None, None),)
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_inlineCallbacksExtraneous = []
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def _extraneous(f: _T_Callable) -> _T_Callable:
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"""
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Mark the given callable as extraneous to inlineCallbacks exception
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reporting; don't show these functions.
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@param f: a function that you NEVER WANT TO SEE AGAIN in ANY TRACEBACK
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reported by Failure.
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@type f: function
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@return: f
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"""
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_inlineCallbacksExtraneous.append(f.__code__)
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return f
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class Failure(BaseException):
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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{frame} attribute contain the traceback 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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Local/global variables in C{frame} will only be captured if
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C{captureVars=True} when constructing the L{Failure}.
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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: Deprecated, always an empty list. Equivalent information can
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be extracted from C{import traceback;
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traceback.extract_stack(your_failure.tb)}
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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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_parents = None
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def __init__(self, exc_value=None, exc_type=None, exc_tb=None, 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 L{None} are allowed.
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If L{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 L{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 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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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:
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# 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._extrapolate(self.value)
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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 getattr(self.value, "__traceback__", None):
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# Python 3
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tb = self.value.__traceback__
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self.tb = tb
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@property
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def frames(self):
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if hasattr(self, "_frames"):
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return self._frames
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frames = self._frames = []
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tb = self.tb
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while tb is not None:
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f = tb.tb_frame
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if self.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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(
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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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)
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tb = tb.tb_next
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return frames
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@frames.setter
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def frames(self, frames):
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self._frames = frames
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@deprecatedProperty(Version("Twisted", 24, 10, 0))
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def stack(self):
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return []
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@stack.setter # type: ignore[no-redef]
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def stack(self, stack):
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del stack
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@property
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def parents(self):
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if self._parents is not None:
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return self._parents
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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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return self._parents
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@parents.setter
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def parents(self, parents):
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self._parents = parents
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def _extrapolate(self, otherFailure):
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"""
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Extrapolate from one failure into another, copying its stack frames.
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@param otherFailure: Another L{Failure}, whose traceback information,
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if any, should be preserved as part of the stack presented by this
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one.
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@type otherFailure: L{Failure}
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"""
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# Copy all infos from that failure (including self._frames).
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self.__dict__ = copy.copy(otherFailure.__dict__)
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@staticmethod
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|
def _withoutTraceback(value: BaseException) -> Failure:
|
||
|
|
"""
|
||
|
|
Create a L{Failure} for an exception without a traceback.
|
||
|
|
|
||
|
|
By restricting the inputs significantly, this constructor runs much
|
||
|
|
faster.
|
||
|
|
"""
|
||
|
|
result = Failure.__new__(Failure)
|
||
|
|
global count
|
||
|
|
count += 1
|
||
|
|
result.captureVars = False
|
||
|
|
result.count = count
|
||
|
|
result.value = value
|
||
|
|
result.type = value.__class__
|
||
|
|
result.tb = None
|
||
|
|
return result
|
||
|
|
|
||
|
|
def trap(self, *errorTypes):
|
||
|
|
"""
|
||
|
|
Trap this failure if its type is in a predetermined list.
|
||
|
|
|
||
|
|
This allows you to trap a Failure in an error callback. It will be
|
||
|
|
automatically re-raised if it is not a type that you expect.
|
||
|
|
|
||
|
|
The reason for having this particular API is because it's very useful
|
||
|
|
in Deferred errback chains::
|
||
|
|
|
||
|
|
def _ebFoo(self, failure):
|
||
|
|
r = failure.trap(Spam, Eggs)
|
||
|
|
print('The Failure is due to either Spam or Eggs!')
|
||
|
|
if r == Spam:
|
||
|
|
print('Spam did it!')
|
||
|
|
elif r == Eggs:
|
||
|
|
print('Eggs did it!')
|
||
|
|
|
||
|
|
If the failure is not a Spam or an Eggs, then the Failure will be
|
||
|
|
'passed on' to the next errback. In Python 2 the Failure will be
|
||
|
|
raised; in Python 3 the underlying exception will be re-raised.
|
||
|
|
|
||
|
|
@type errorTypes: L{Exception}
|
||
|
|
"""
|
||
|
|
error = self.check(*errorTypes)
|
||
|
|
if not error:
|
||
|
|
self.raiseException()
|
||
|
|
return error
|
||
|
|
|
||
|
|
def check(self, *errorTypes):
|
||
|
|
"""
|
||
|
|
Check if this failure's type is in a predetermined list.
|
||
|
|
|
||
|
|
@type errorTypes: list of L{Exception} classes or
|
||
|
|
fully-qualified class names.
|
||
|
|
@returns: the matching L{Exception} type, or None if no match.
|
||
|
|
"""
|
||
|
|
for error in errorTypes:
|
||
|
|
err = error
|
||
|
|
if inspect.isclass(error) and issubclass(error, Exception):
|
||
|
|
err = reflect.qual(error)
|
||
|
|
if err in self.parents:
|
||
|
|
return error
|
||
|
|
return None
|
||
|
|
|
||
|
|
def raiseException(self) -> NoReturn:
|
||
|
|
"""
|
||
|
|
raise the original exception, preserving traceback
|
||
|
|
information if available.
|
||
|
|
"""
|
||
|
|
raise self.value.with_traceback(self.tb)
|
||
|
|
|
||
|
|
@_extraneous
|
||
|
|
def throwExceptionIntoGenerator(self, g):
|
||
|
|
"""
|
||
|
|
Throw the original exception into the given generator,
|
||
|
|
preserving traceback information if available.
|
||
|
|
|
||
|
|
@return: The next value yielded from the generator.
|
||
|
|
@raise StopIteration: If there are no more values in the generator.
|
||
|
|
@raise anything else: Anything that the generator raises.
|
||
|
|
"""
|
||
|
|
return g.throw(self.value.with_traceback(self.tb))
|
||
|
|
|
||
|
|
def __repr__(self) -> str:
|
||
|
|
return "<{} {}: {}>".format(
|
||
|
|
reflect.qual(self.__class__),
|
||
|
|
reflect.qual(self.type),
|
||
|
|
self.getErrorMessage(),
|
||
|
|
)
|
||
|
|
|
||
|
|
def __str__(self) -> str:
|
||
|
|
return "[Failure instance: %s]" % self.getBriefTraceback()
|
||
|
|
|
||
|
|
def __setstate__(self, state):
|
||
|
|
if "stack" in state:
|
||
|
|
state.pop("stack")
|
||
|
|
state["_parents"] = state.pop("parents")
|
||
|
|
state["_frames"] = state.pop("frames")
|
||
|
|
self.__dict__.update(state)
|
||
|
|
|
||
|
|
def __getstate__(self):
|
||
|
|
"""
|
||
|
|
Avoid pickling objects in the traceback.
|
||
|
|
|
||
|
|
This is not called direclty by pickle, since C{BaseException}
|
||
|
|
implements reduce; instead, pickle calls C{Failure.__reduce__} which
|
||
|
|
then calls this API.
|
||
|
|
"""
|
||
|
|
# Make sure _parents field is populated:
|
||
|
|
_ = self.parents
|
||
|
|
|
||
|
|
c = self.__dict__.copy()
|
||
|
|
|
||
|
|
# Backwards compatibility with old code, e.g. for Perspective Broker:
|
||
|
|
c["parents"] = c.pop("_parents")
|
||
|
|
c["stack"] = []
|
||
|
|
|
||
|
|
if "_frames" in c:
|
||
|
|
c.pop("_frames")
|
||
|
|
|
||
|
|
if self.captureVars:
|
||
|
|
c["frames"] = [
|
||
|
|
[
|
||
|
|
v[0],
|
||
|
|
v[1],
|
||
|
|
v[2],
|
||
|
|
_safeReprVars(v[3]),
|
||
|
|
_safeReprVars(v[4]),
|
||
|
|
]
|
||
|
|
for v in self.frames
|
||
|
|
]
|
||
|
|
else:
|
||
|
|
c["frames"] = self.frames
|
||
|
|
|
||
|
|
# Added 2003-06-23. See comment above in __init__
|
||
|
|
c["tb"] = None
|
||
|
|
|
||
|
|
c["pickled"] = 1
|
||
|
|
return c
|
||
|
|
|
||
|
|
def __reduce__(self):
|
||
|
|
# BaseException implements a __reduce__ (in C, technically), so we need
|
||
|
|
# to override this to get pickling working.
|
||
|
|
return (partial(Failure.__new__, Failure), (), self.__getstate__())
|
||
|
|
|
||
|
|
def cleanFailure(self):
|
||
|
|
"""
|
||
|
|
Remove references to other objects, replacing them with strings.
|
||
|
|
|
||
|
|
On Python 3, this will also set the C{__traceback__} attribute of the
|
||
|
|
exception instance to L{None}.
|
||
|
|
"""
|
||
|
|
state = self.__getstate__()
|
||
|
|
state["_frames"] = state.pop("frames")
|
||
|
|
self.__dict__ = state
|
||
|
|
if getattr(self.value, "__traceback__", None):
|
||
|
|
# Python 3
|
||
|
|
self.value.__traceback__ = None
|
||
|
|
|
||
|
|
def getTracebackObject(self):
|
||
|
|
"""
|
||
|
|
Get an object that represents this Failure's stack that can be passed
|
||
|
|
to traceback.extract_tb.
|
||
|
|
|
||
|
|
If the original traceback object is still present, return that. If this
|
||
|
|
traceback object has been lost but we still have the information,
|
||
|
|
return a fake traceback object (see L{_Traceback}). If there is no
|
||
|
|
traceback information at all, return None.
|
||
|
|
"""
|
||
|
|
if self.tb is not None:
|
||
|
|
return self.tb
|
||
|
|
elif len(self.frames) > 0:
|
||
|
|
return _Traceback(self.frames)
|
||
|
|
else:
|
||
|
|
return None
|
||
|
|
|
||
|
|
def getErrorMessage(self) -> str:
|
||
|
|
"""
|
||
|
|
Get a string of the exception which caused this Failure.
|
||
|
|
"""
|
||
|
|
if isinstance(self.value, Failure):
|
||
|
|
return self.value.getErrorMessage()
|
||
|
|
return reflect.safe_str(self.value)
|
||
|
|
|
||
|
|
def getBriefTraceback(self) -> str:
|
||
|
|
io = StringIO()
|
||
|
|
self.printBriefTraceback(file=io)
|
||
|
|
return io.getvalue()
|
||
|
|
|
||
|
|
def getTraceback(self, elideFrameworkCode: int = 0, detail: str = "default") -> str:
|
||
|
|
io = StringIO()
|
||
|
|
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: Deprecated, ignored.
|
||
|
|
|
||
|
|
@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:
|
||
|
|
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(f"{reflect.qual(self.type)}: {reflect.safe_str(self.value)}\n")
|
||
|
|
|
||
|
|
# 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 BaseException:
|
||
|
|
strrepr = "broken str"
|
||
|
|
print(
|
||
|
|
"Jumping into debugger for post-mortem of exception '{}':".format(
|
||
|
|
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
|