content/test/gpu/gpu_tests/exception_formatter.py

   1 # Copyright 2014 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 """Print prettier and more detailed exceptions. Copied from Telemetry."""
   6
   7 import math
   8 import os
   9 import sys
  10 import traceback
  11
  12 from telemetry.core import exceptions
  13 from telemetry.core import util
  14
  15
  16 def PrintFormattedException(exception_class=None, exception=None, tb=None,
  17                             msg=None):
  18   assert bool(exception_class) == bool(exception) == bool(tb), (
  19       'Must specify all or none of exception_class, exception, and tb')
  20
  21   if not exception_class:
  22     exception_class, exception, tb = sys.exc_info()
  23
  24   if exception_class == exceptions.IntentionalException:
  25     return
  26
  27   def _GetFinalFrame(tb_level):
  28     while tb_level.tb_next:
  29       tb_level = tb_level.tb_next
  30     return tb_level.tb_frame
  31
  32   processed_tb = traceback.extract_tb(tb)
  33   frame = _GetFinalFrame(tb)
  34   exception_list = traceback.format_exception_only(exception_class, exception)
  35   exception_string = '\n'.join(l.strip() for l in exception_list)
  36
  37   if msg:
  38     print >> sys.stderr
  39     print >> sys.stderr, msg
  40
  41   _PrintFormattedTrace(processed_tb, frame, exception_string)
  42
  43
  44 def PrintFormattedFrame(frame, exception_string=None):
  45   _PrintFormattedTrace(traceback.extract_stack(frame), frame, exception_string)
  46
  47
  48 def _PrintFormattedTrace(processed_tb, frame, exception_string=None):
  49   """Prints an Exception in a more useful format than the default.
  50
  51   TODO(tonyg): Consider further enhancements. For instance:
  52     - Report stacks to maintainers like depot_tools does.
  53     - Add a debug flag to automatically start pdb upon exception.
  54   """
  55   print >> sys.stderr
  56
  57   # Format the traceback.
  58   base_dir = os.path.abspath(util.GetChromiumSrcDir())
  59   print >> sys.stderr, 'Traceback (most recent call last):'
  60   for filename, line, function, text in processed_tb:
  61     filename = os.path.abspath(filename)
  62     if filename.startswith(base_dir):
  63       filename = filename[len(base_dir)+1:]
  64     print >> sys.stderr, '  %s at %s:%d' % (function, filename, line)
  65     print >> sys.stderr, '    %s' % text
  66
  67   # Format the exception.
  68   if exception_string:
  69     print >> sys.stderr, exception_string
  70
  71   # Format the locals.
  72   local_variables = [(variable, value) for variable, value in
  73                      frame.f_locals.iteritems() if variable != 'self']
  74   print >> sys.stderr
  75   print >> sys.stderr, 'Locals:'
  76   if local_variables:
  77     longest_variable = max(len(v) for v, _ in local_variables)
  78     for variable, value in sorted(local_variables):
  79       value = repr(value)
  80       possibly_truncated_value = _AbbreviateMiddleOfString(value, ' ... ', 1024)
  81       truncation_indication = ''
  82       if len(possibly_truncated_value) != len(value):
  83         truncation_indication = ' (truncated)'
  84       print >> sys.stderr, '  %s: %s%s' % (variable.ljust(longest_variable + 1),
  85                                            possibly_truncated_value,
  86                                            truncation_indication)
  87   else:
  88     print >> sys.stderr, '  No locals!'
  89
  90   print >> sys.stderr
  91   sys.stderr.flush()
  92
  93
  94 def _AbbreviateMiddleOfString(target, middle, max_length):
  95   if max_length < 0:
  96     raise ValueError('Must provide positive max_length')
  97   if len(middle) > max_length:
  98     raise ValueError('middle must not be greater than max_length')
  99
 100   if len(target) <= max_length:
 101     return target
 102   half_length = (max_length - len(middle)) / 2.
 103   return (target[:int(math.floor(half_length))] + middle +
 104           target[-int(math.ceil(half_length)):])