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# -*- coding: utf-8 -*-
Implements the debug interface for Jinja. This module does some pretty
ugly stuff with the Python traceback system in order to achieve tracebacks
with correct line numbers, locals and contents.
:copyright: (c) 2009 by the Jinja Team.
:license: BSD.
import sys
from jinja2.utils import CodeType, missing
def translate_exception(exc_info):
"""If passed an exc_info it will automatically rewrite the exceptions
all the way down to the correct line numbers and frames.
result_tb = prev_tb = None
initial_tb = tb = exc_info[2].tb_next
while tb is not None:
template = tb.tb_frame.f_globals.get('__jinja_template__')
if template is not None:
lineno = template.get_corresponding_lineno(tb.tb_lineno)
tb = fake_exc_info(exc_info[:2] + (tb,), template.filename,
lineno, prev_tb)[2]
if result_tb is None:
result_tb = tb
prev_tb = tb
tb = tb.tb_next
return exc_info[:2] + (result_tb or initial_tb,)
def fake_exc_info(exc_info, filename, lineno, tb_back=None):
"""Helper for `translate_exception`."""
exc_type, exc_value, tb = exc_info
# figure the real context out
real_locals = tb.tb_frame.f_locals.copy()
ctx = real_locals.get('context')
if ctx:
locals = ctx.get_all()
locals = {}
for name, value in real_locals.iteritems():
if name.startswith('l_') and value is not missing:
locals[name[2:]] = value
# if there is a local called __jinja_exception__, we get
# rid of it to not break the debug functionality.
locals.pop('__jinja_exception__', None)
# assamble fake globals we need
globals = {
'__name__': filename,
'__file__': filename,
'__jinja_exception__': exc_info[:2]
# and fake the exception
code = compile('\n' * (lineno - 1) + 'raise __jinja_exception__[0], ' +
'__jinja_exception__[1]', filename, 'exec')
# if it's possible, change the name of the code. This won't work
# on some python environments such as google appengine
function = tb.tb_frame.f_code.co_name
if function == 'root':
location = 'top-level template code'
elif function.startswith('block_'):
location = 'block "%s"' % function[6:]
location = 'template'
code = CodeType(0, code.co_nlocals, code.co_stacksize,
code.co_flags, code.co_code, code.co_consts,
code.co_names, code.co_varnames, filename,
location, code.co_firstlineno,
code.co_lnotab, (), ())
# execute the code and catch the new traceback
exec code in globals, locals
exc_info = sys.exc_info()
new_tb = exc_info[2].tb_next
# now we can patch the exc info accordingly
if tb_set_next is not None:
if tb_back is not None:
tb_set_next(tb_back, new_tb)
if tb is not None:
tb_set_next(new_tb, tb.tb_next)
# return without this frame
return exc_info[:2] + (new_tb,)
def _init_ugly_crap():
"""This function implements a few ugly things so that we can patch the
traceback objects. The function returned allows resetting `tb_next` on
any python traceback object.
import ctypes
from types import TracebackType
# figure out side of _Py_ssize_t
if hasattr(ctypes.pythonapi, 'Py_InitModule4_64'):
_Py_ssize_t = ctypes.c_int64
_Py_ssize_t = ctypes.c_int
# regular python
class _PyObject(ctypes.Structure):
_PyObject._fields_ = [
('ob_refcnt', _Py_ssize_t),
('ob_type', ctypes.POINTER(_PyObject))
# python with trace
if object.__basicsize__ != ctypes.sizeof(_PyObject):
class _PyObject(ctypes.Structure):
_PyObject._fields_ = [
('_ob_next', ctypes.POINTER(_PyObject)),
('_ob_prev', ctypes.POINTER(_PyObject)),
('ob_refcnt', _Py_ssize_t),
('ob_type', ctypes.POINTER(_PyObject))
class _Traceback(_PyObject):
_Traceback._fields_ = [
('tb_next', ctypes.POINTER(_Traceback)),
('tb_frame', ctypes.POINTER(_PyObject)),
('tb_lasti', ctypes.c_int),
('tb_lineno', ctypes.c_int)
def tb_set_next(tb, next):
"""Set the tb_next attribute of a traceback object."""
if not (isinstance(tb, TracebackType) and
(next is None or isinstance(next, TracebackType))):
raise TypeError('tb_set_next arguments must be traceback objects')
obj = _Traceback.from_address(id(tb))
if tb.tb_next is not None:
old = _Traceback.from_address(id(tb.tb_next))
old.ob_refcnt -= 1
if next is None:
obj.tb_next = ctypes.POINTER(_Traceback)()
next = _Traceback.from_address(id(next))
next.ob_refcnt += 1
obj.tb_next = ctypes.pointer(next)
return tb_set_next
# try to get a tb_set_next implementation
from jinja2._speedups import tb_set_next
except ImportError:
tb_set_next = _init_ugly_crap()
tb_set_next = None
del _init_ugly_crap
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