sdk/platform-tools/systrace/catapult/telemetry/third_party/web-page-replay/exception_formatter.py

   1 # Copyright 2015 Google Inc. All Rights Reserved.
   2 #
   3 # Licensed under the Apache License, Version 2.0 (the "License");
   4 # you may not use this file except in compliance with the License.
   5 # You may obtain a copy of the License at
   6 #
   7 #      http://www.apache.org/licenses/LICENSE-2.0
   8 #
   9 # Unless required by applicable law or agreed to in writing, software
  10 # distributed under the License is distributed on an "AS IS" BASIS,
  11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 # See the License for the specific language governing permissions and
  13 # limitations under the License.
  14
  15 import math
  16 import os
  17 import sys
  18 import traceback
  19
  20
  21 def PrintFormattedException(msg=None):
  22   exception_class, exception, tb = sys.exc_info()
  23
  24   def _GetFinalFrame(tb_level):
  25     while tb_level.tb_next:
  26       tb_level = tb_level.tb_next
  27     return tb_level.tb_frame
  28
  29   processed_tb = traceback.extract_tb(tb)
  30   frame = _GetFinalFrame(tb)
  31   exception_list = traceback.format_exception_only(exception_class, exception)
  32   exception_string = '\n'.join(l.strip() for l in exception_list)
  33
  34   if msg:
  35     print >> sys.stderr
  36     print >> sys.stderr, msg
  37
  38   _PrintFormattedTrace(processed_tb, frame, exception_string)
  39
  40 def PrintFormattedFrame(frame, exception_string=None):
  41   _PrintFormattedTrace(traceback.extract_stack(frame), frame, exception_string)
  42
  43
  44 def _PrintFormattedTrace(processed_tb, frame, exception_string=None):
  45   """Prints an Exception in a more useful format than the default.
  46   """
  47   print >> sys.stderr
  48
  49   # Format the traceback.
  50   base_dir = os.path.dirname(__file__)
  51   print >> sys.stderr, 'Traceback (most recent call last):'
  52   for filename, line, function, text in processed_tb:
  53     filename = os.path.abspath(filename)
  54     if filename.startswith(base_dir):
  55       filename = filename[len(base_dir)+1:]
  56     print >> sys.stderr, '  %s at %s:%d' % (function, filename, line)
  57     print >> sys.stderr, '    %s' % text
  58
  59   # Format the exception.
  60   if exception_string:
  61     print >> sys.stderr, exception_string
  62
  63   # Format the locals.
  64   local_variables = [(variable, value) for variable, value in
  65                      frame.f_locals.iteritems() if variable != 'self']
  66   print >> sys.stderr
  67   print >> sys.stderr, 'Locals:'
  68   if local_variables:
  69     longest_variable = max(len(v) for v, _ in local_variables)
  70     for variable, value in sorted(local_variables):
  71       value = repr(value)
  72       possibly_truncated_value = _AbbreviateMiddleOfString(value, ' ... ', 1024)
  73       truncation_indication = ''
  74       if len(possibly_truncated_value) != len(value):
  75         truncation_indication = ' (truncated)'
  76       print >> sys.stderr, '  %s: %s%s' % (variable.ljust(longest_variable + 1),
  77                                            possibly_truncated_value,
  78                                            truncation_indication)
  79   else:
  80     print >> sys.stderr, '  No locals!'
  81
  82   print >> sys.stderr
  83   sys.stderr.flush()
  84
  85
  86 def _AbbreviateMiddleOfString(target, middle, max_length):
  87   if max_length < 0:
  88     raise ValueError('Must provide positive max_length')
  89   if len(middle) > max_length:
  90     raise ValueError('middle must not be greater than max_length')
  91
  92   if len(target) <= max_length:
  93     return target
  94   half_length = (max_length - len(middle)) / 2.
  95   return (target[:int(math.floor(half_length))] + middle +
  96           target[-int(math.ceil(half_length)):])