1 files changed, 103 insertions, 0 deletions
diff --git a/catapult/telemetry/telemetry/internal/util/exception_formatter.py b/catapult/telemetry/telemetry/internal/util/exception_formatter.py
new file mode 100644
index 00000000..fe036c84
--- /dev/null
+++ b/catapult/telemetry/telemetry/internal/util/exception_formatter.py
@@ -0,0 +1,103 @@
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Print prettier and more detailed exceptions."""
+
+import logging
+import math
+import os
+import sys
+import traceback
+
+from telemetry.core import exceptions
+
+
+def PrintFormattedException(exception_class=None, exception=None, tb=None,
+                            msg=None):
+  logging.info('Try printing formatted exception: %s %s %s' %
+               (exception_class, exception, tb))
+  assert bool(exception_class) == bool(exception) == bool(tb), (
+      'Must specify all or none of exception_class, exception, and tb')
+
+  if not exception_class:
+    exception_class, exception, tb = sys.exc_info()
+
+  if exception_class == exceptions.IntentionalException:
+    return
+
+  def _GetFinalFrame(tb_level):
+    while tb_level.tb_next:
+      tb_level = tb_level.tb_next
+    return tb_level.tb_frame
+
+  processed_tb = traceback.extract_tb(tb)
+  frame = _GetFinalFrame(tb)
+  exception_list = traceback.format_exception_only(exception_class, exception)
+  exception_string = '\n'.join(l.strip() for l in exception_list)
+
+  if msg:
+    print >> sys.stderr
+    print >> sys.stderr, msg
+
+  _PrintFormattedTrace(processed_tb, frame, exception_string)
+
+
+def PrintFormattedFrame(frame, exception_string=None):
+  _PrintFormattedTrace(traceback.extract_stack(frame), frame, exception_string)
+
+
+def _PrintFormattedTrace(processed_tb, frame, exception_string=None):
+  """Prints an Exception in a more useful format than the default.
+
+  TODO(tonyg): Consider further enhancements. For instance:
+    - Report stacks to maintainers like depot_tools does.
+    - Add a debug flag to automatically start pdb upon exception.
+  """
+  print >> sys.stderr
+
+  # Format the traceback.
+  print >> sys.stderr, 'Traceback (most recent call last):'
+  for filename, line, function, text in processed_tb:
+    filename = os.path.abspath(filename)
+    print >> sys.stderr, '  %s at %s:%d' % (function, filename, line)
+    print >> sys.stderr, '    %s' % text
+
+  # Format the exception.
+  if exception_string:
+    print >> sys.stderr, exception_string
+
+  # Format the locals.
+  local_variables = [(variable, value) for variable, value in
+                     frame.f_locals.iteritems() if variable != 'self']
+  print >> sys.stderr
+  print >> sys.stderr, 'Locals:'
+  if local_variables:
+    longest_variable = max(len(v) for v, _ in local_variables)
+    for variable, value in sorted(local_variables):
+      value = repr(value)
+      possibly_truncated_value = _AbbreviateMiddleOfString(value, ' ... ', 1024)
+      truncation_indication = ''
+      if len(possibly_truncated_value) != len(value):
+        truncation_indication = ' (truncated)'
+      print >> sys.stderr, '  %s: %s%s' % (variable.ljust(longest_variable + 1),
+                                           possibly_truncated_value,
+                                           truncation_indication)
+  else:
+    print >> sys.stderr, '  No locals!'
+
+  print >> sys.stderr
+  sys.stderr.flush()
+
+
+def _AbbreviateMiddleOfString(target, middle, max_length):
+  if max_length < 0:
+    raise ValueError('Must provide positive max_length')
+  if len(middle) > max_length:
+    raise ValueError('middle must not be greater than max_length')
+
+  if len(target) <= max_length:
+    return target
+  half_length = (max_length - len(middle)) / 2.
+  return (target[:int(math.floor(half_length))] + middle +
+          target[-int(math.ceil(half_length)):])