third_party/jinja2/debug.py

   1 # -*- coding: utf-8 -*-
   2 """
   3     jinja2.debug
   4     ~~~~~~~~~~~~
   5
   6     Implements the debug interface for Jinja.  This module does some pretty
   7     ugly stuff with the Python traceback system in order to achieve tracebacks
   8     with correct line numbers, locals and contents.
   9
  10     :copyright: (c) 2010 by the Jinja Team.
  11     :license: BSD, see LICENSE for more details.
  12 """
  13 import sys
  14 import traceback
  15 from types import TracebackType
  16 from jinja2.utils import missing, internal_code
  17 from jinja2.exceptions import TemplateSyntaxError
  18 from jinja2._compat import iteritems, reraise, code_type
  19
  20 # on pypy we can take advantage of transparent proxies
  21 try:
  22     from __pypy__ import tproxy
  23 except ImportError:
  24     tproxy = None
  25
  26
  27 # how does the raise helper look like?
  28 try:
  29     exec("raise TypeError, 'foo'")
  30 except SyntaxError:
  31     raise_helper = 'raise __jinja_exception__[1]'
  32 except TypeError:
  33     raise_helper = 'raise __jinja_exception__[0], __jinja_exception__[1]'
  34
  35
  36 class TracebackFrameProxy(object):
  37     """Proxies a traceback frame."""
  38
  39     def __init__(self, tb):
  40         self.tb = tb
  41         self._tb_next = None
  42
  43     @property
  44     def tb_next(self):
  45         return self._tb_next
  46
  47     def set_next(self, next):
  48         if tb_set_next is not None:
  49             try:
  50                 tb_set_next(self.tb, next and next.tb or None)
  51             except Exception:
  52                 # this function can fail due to all the hackery it does
  53                 # on various python implementations.  We just catch errors
  54                 # down and ignore them if necessary.
  55                 pass
  56         self._tb_next = next
  57
  58     @property
  59     def is_jinja_frame(self):
  60         return '__jinja_template__' in self.tb.tb_frame.f_globals
  61
  62     def __getattr__(self, name):
  63         return getattr(self.tb, name)
  64
  65
  66 def make_frame_proxy(frame):
  67     proxy = TracebackFrameProxy(frame)
  68     if tproxy is None:
  69         return proxy
  70     def operation_handler(operation, *args, **kwargs):
  71         if operation in ('__getattribute__', '__getattr__'):
  72             return getattr(proxy, args[0])
  73         elif operation == '__setattr__':
  74             proxy.__setattr__(*args, **kwargs)
  75         else:
  76             return getattr(proxy, operation)(*args, **kwargs)
  77     return tproxy(TracebackType, operation_handler)
  78
  79
  80 class ProcessedTraceback(object):
  81     """Holds a Jinja preprocessed traceback for printing or reraising."""
  82
  83     def __init__(self, exc_type, exc_value, frames):
  84         assert frames, 'no frames for this traceback?'
  85         self.exc_type = exc_type
  86         self.exc_value = exc_value
  87         self.frames = frames
  88
  89         # newly concatenate the frames (which are proxies)
  90         prev_tb = None
  91         for tb in self.frames:
  92             if prev_tb is not None:
  93                 prev_tb.set_next(tb)
  94             prev_tb = tb
  95         prev_tb.set_next(None)
  96
  97     def render_as_text(self, limit=None):
  98         """Return a string with the traceback."""
  99         lines = traceback.format_exception(self.exc_type, self.exc_value,
 100                                            self.frames[0], limit=limit)
 101         return ''.join(lines).rstrip()
 102
 103     def render_as_html(self, full=False):
 104         """Return a unicode string with the traceback as rendered HTML."""
 105         from jinja2.debugrenderer import render_traceback
 106         return u'%s\n\n<!--\n%s\n-->' % (
 107             render_traceback(self, full=full),
 108             self.render_as_text().decode('utf-8', 'replace')
 109         )
 110
 111     @property
 112     def is_template_syntax_error(self):
 113         """`True` if this is a template syntax error."""
 114         return isinstance(self.exc_value, TemplateSyntaxError)
 115
 116     @property
 117     def exc_info(self):
 118         """Exception info tuple with a proxy around the frame objects."""
 119         return self.exc_type, self.exc_value, self.frames[0]
 120
 121     @property
 122     def standard_exc_info(self):
 123         """Standard python exc_info for re-raising"""
 124         tb = self.frames[0]
 125         # the frame will be an actual traceback (or transparent proxy) if
 126         # we are on pypy or a python implementation with support for tproxy
 127         if type(tb) is not TracebackType:
 128             tb = tb.tb
 129         return self.exc_type, self.exc_value, tb
 130
 131
 132 def make_traceback(exc_info, source_hint=None):
 133     """Creates a processed traceback object from the exc_info."""
 134     exc_type, exc_value, tb = exc_info
 135     if isinstance(exc_value, TemplateSyntaxError):
 136         exc_info = translate_syntax_error(exc_value, source_hint)
 137         initial_skip = 0
 138     else:
 139         initial_skip = 1
 140     return translate_exception(exc_info, initial_skip)
 141
 142
 143 def translate_syntax_error(error, source=None):
 144     """Rewrites a syntax error to please traceback systems."""
 145     error.source = source
 146     error.translated = True
 147     exc_info = (error.__class__, error, None)
 148     filename = error.filename
 149     if filename is None:
 150         filename = '<unknown>'
 151     return fake_exc_info(exc_info, filename, error.lineno)
 152
 153
 154 def translate_exception(exc_info, initial_skip=0):
 155     """If passed an exc_info it will automatically rewrite the exceptions
 156     all the way down to the correct line numbers and frames.
 157     """
 158     tb = exc_info[2]
 159     frames = []
 160
 161     # skip some internal frames if wanted
 162     for x in range(initial_skip):
 163         if tb is not None:
 164             tb = tb.tb_next
 165     initial_tb = tb
 166
 167     while tb is not None:
 168         # skip frames decorated with @internalcode.  These are internal
 169         # calls we can't avoid and that are useless in template debugging
 170         # output.
 171         if tb.tb_frame.f_code in internal_code:
 172             tb = tb.tb_next
 173             continue
 174
 175         # save a reference to the next frame if we override the current
 176         # one with a faked one.
 177         next = tb.tb_next
 178
 179         # fake template exceptions
 180         template = tb.tb_frame.f_globals.get('__jinja_template__')
 181         if template is not None:
 182             lineno = template.get_corresponding_lineno(tb.tb_lineno)
 183             tb = fake_exc_info(exc_info[:2] + (tb,), template.filename,
 184                                lineno)[2]
 185
 186         frames.append(make_frame_proxy(tb))
 187         tb = next
 188
 189     # if we don't have any exceptions in the frames left, we have to
 190     # reraise it unchanged.
 191     # XXX: can we backup here?  when could this happen?
 192     if not frames:
 193         reraise(exc_info[0], exc_info[1], exc_info[2])
 194
 195     return ProcessedTraceback(exc_info[0], exc_info[1], frames)
 196
 197
 198 def fake_exc_info(exc_info, filename, lineno):
 199     """Helper for `translate_exception`."""
 200     exc_type, exc_value, tb = exc_info
 201
 202     # figure the real context out
 203     if tb is not None:
 204         real_locals = tb.tb_frame.f_locals.copy()
 205         ctx = real_locals.get('context')
 206         if ctx:
 207             locals = ctx.get_all()
 208         else:
 209             locals = {}
 210         for name, value in iteritems(real_locals):
 211             if name.startswith('l_') and value is not missing:
 212                 locals[name[2:]] = value
 213
 214         # if there is a local called __jinja_exception__, we get
 215         # rid of it to not break the debug functionality.
 216         locals.pop('__jinja_exception__', None)
 217     else:
 218         locals = {}
 219
 220     # assamble fake globals we need
 221     globals = {
 222         '__name__':             filename,
 223         '__file__':             filename,
 224         '__jinja_exception__':  exc_info[:2],
 225
 226         # we don't want to keep the reference to the template around
 227         # to not cause circular dependencies, but we mark it as Jinja
 228         # frame for the ProcessedTraceback
 229         '__jinja_template__':   None
 230     }
 231
 232     # and fake the exception
 233     code = compile('\n' * (lineno - 1) + raise_helper, filename, 'exec')
 234
 235     # if it's possible, change the name of the code.  This won't work
 236     # on some python environments such as google appengine
 237     try:
 238         if tb is None:
 239             location = 'template'
 240         else:
 241             function = tb.tb_frame.f_code.co_name
 242             if function == 'root':
 243                 location = 'top-level template code'
 244             elif function.startswith('block_'):
 245                 location = 'block "%s"' % function[6:]
 246             else:
 247                 location = 'template'
 248         code = code_type(0, code.co_nlocals, code.co_stacksize,
 249                          code.co_flags, code.co_code, code.co_consts,
 250                          code.co_names, code.co_varnames, filename,
 251                          location, code.co_firstlineno,
 252                          code.co_lnotab, (), ())
 253     except:
 254         pass
 255
 256     # execute the code and catch the new traceback
 257     try:
 258         exec(code, globals, locals)
 259     except:
 260         exc_info = sys.exc_info()
 261         new_tb = exc_info[2].tb_next
 262
 263     # return without this frame
 264     return exc_info[:2] + (new_tb,)
 265
 266
 267 def _init_ugly_crap():
 268     """This function implements a few ugly things so that we can patch the
 269     traceback objects.  The function returned allows resetting `tb_next` on
 270     any python traceback object.  Do not attempt to use this on non cpython
 271     interpreters
 272     """
 273     import ctypes
 274     from types import TracebackType
 275
 276     # figure out side of _Py_ssize_t
 277     if hasattr(ctypes.pythonapi, 'Py_InitModule4_64'):
 278         _Py_ssize_t = ctypes.c_int64
 279     else:
 280         _Py_ssize_t = ctypes.c_int
 281
 282     # regular python
 283     class _PyObject(ctypes.Structure):
 284         pass
 285     _PyObject._fields_ = [
 286         ('ob_refcnt', _Py_ssize_t),
 287         ('ob_type', ctypes.POINTER(_PyObject))
 288     ]
 289
 290     # python with trace
 291     if hasattr(sys, 'getobjects'):
 292         class _PyObject(ctypes.Structure):
 293             pass
 294         _PyObject._fields_ = [
 295             ('_ob_next', ctypes.POINTER(_PyObject)),
 296             ('_ob_prev', ctypes.POINTER(_PyObject)),
 297             ('ob_refcnt', _Py_ssize_t),
 298             ('ob_type', ctypes.POINTER(_PyObject))
 299         ]
 300
 301     class _Traceback(_PyObject):
 302         pass
 303     _Traceback._fields_ = [
 304         ('tb_next', ctypes.POINTER(_Traceback)),
 305         ('tb_frame', ctypes.POINTER(_PyObject)),
 306         ('tb_lasti', ctypes.c_int),
 307         ('tb_lineno', ctypes.c_int)
 308     ]
 309
 310     def tb_set_next(tb, next):
 311         """Set the tb_next attribute of a traceback object."""
 312         if not (isinstance(tb, TracebackType) and
 313                 (next is None or isinstance(next, TracebackType))):
 314             raise TypeError('tb_set_next arguments must be traceback objects')
 315         obj = _Traceback.from_address(id(tb))
 316         if tb.tb_next is not None:
 317             old = _Traceback.from_address(id(tb.tb_next))
 318             old.ob_refcnt -= 1
 319         if next is None:
 320             obj.tb_next = ctypes.POINTER(_Traceback)()
 321         else:
 322             next = _Traceback.from_address(id(next))
 323             next.ob_refcnt += 1
 324             obj.tb_next = ctypes.pointer(next)
 325
 326     return tb_set_next
 327
 328
 329 # try to get a tb_set_next implementation if we don't have transparent
 330 # proxies.
 331 tb_set_next = None
 332 if tproxy is None:
 333     try:
 334         tb_set_next = _init_ugly_crap()
 335     except:
 336         pass
 337     del _init_ugly_crap