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/thirdparty/breakpad/third_party/protobuf/protobuf/python/stubout.py

http://github.com/tomahawk-player/tomahawk
Python | 140 lines | 117 code | 2 blank | 21 comment | 1 complexity | 91fa2b8d8f8b79c06acf825139c709cf MD5 | raw file
  1#!/usr/bin/python2.4
  2#
  3# Copyright 2008 Google Inc.
  4#
  5# Licensed under the Apache License, Version 2.0 (the "License");
  6# you may not use this file except in compliance with the License.
  7# You may obtain a copy of the License at
  8#
  9#      http://www.apache.org/licenses/LICENSE-2.0
 10#
 11# Unless required by applicable law or agreed to in writing, software
 12# distributed under the License is distributed on an "AS IS" BASIS,
 13# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14# See the License for the specific language governing permissions and
 15# limitations under the License.
 16
 17# This file is used for testing.  The original is at:
 18#   http://code.google.com/p/pymox/
 19
 20class StubOutForTesting:
 21  """Sample Usage:
 22     You want os.path.exists() to always return true during testing.
 23
 24     stubs = StubOutForTesting()
 25     stubs.Set(os.path, 'exists', lambda x: 1)
 26       ...
 27     stubs.UnsetAll()
 28
 29     The above changes os.path.exists into a lambda that returns 1.  Once
 30     the ... part of the code finishes, the UnsetAll() looks up the old value
 31     of os.path.exists and restores it.
 32
 33  """
 34  def __init__(self):
 35    self.cache = []
 36    self.stubs = []
 37
 38  def __del__(self):
 39    self.SmartUnsetAll()
 40    self.UnsetAll()
 41
 42  def SmartSet(self, obj, attr_name, new_attr):
 43    """Replace obj.attr_name with new_attr. This method is smart and works
 44       at the module, class, and instance level while preserving proper
 45       inheritance. It will not stub out C types however unless that has been
 46       explicitly allowed by the type.
 47
 48       This method supports the case where attr_name is a staticmethod or a
 49       classmethod of obj.
 50
 51       Notes:
 52      - If obj is an instance, then it is its class that will actually be
 53        stubbed. Note that the method Set() does not do that: if obj is
 54        an instance, it (and not its class) will be stubbed.
 55      - The stubbing is using the builtin getattr and setattr. So, the __get__
 56        and __set__ will be called when stubbing (TODO: A better idea would
 57        probably be to manipulate obj.__dict__ instead of getattr() and
 58        setattr()).
 59
 60       Raises AttributeError if the attribute cannot be found.
 61    """
 62    if (inspect.ismodule(obj) or
 63        (not inspect.isclass(obj) and obj.__dict__.has_key(attr_name))):
 64      orig_obj = obj
 65      orig_attr = getattr(obj, attr_name)
 66
 67    else:
 68      if not inspect.isclass(obj):
 69        mro = list(inspect.getmro(obj.__class__))
 70      else:
 71        mro = list(inspect.getmro(obj))
 72
 73      mro.reverse()
 74
 75      orig_attr = None
 76
 77      for cls in mro:
 78        try:
 79          orig_obj = cls
 80          orig_attr = getattr(obj, attr_name)
 81        except AttributeError:
 82          continue
 83
 84    if orig_attr is None:
 85      raise AttributeError("Attribute not found.")
 86
 87    # Calling getattr() on a staticmethod transforms it to a 'normal' function.
 88    # We need to ensure that we put it back as a staticmethod.
 89    old_attribute = obj.__dict__.get(attr_name)
 90    if old_attribute is not None and isinstance(old_attribute, staticmethod):
 91      orig_attr = staticmethod(orig_attr)
 92
 93    self.stubs.append((orig_obj, attr_name, orig_attr))
 94    setattr(orig_obj, attr_name, new_attr)
 95
 96  def SmartUnsetAll(self):
 97    """Reverses all the SmartSet() calls, restoring things to their original
 98    definition.  Its okay to call SmartUnsetAll() repeatedly, as later calls
 99    have no effect if no SmartSet() calls have been made.
100
101    """
102    self.stubs.reverse()
103
104    for args in self.stubs:
105      setattr(*args)
106
107    self.stubs = []
108
109  def Set(self, parent, child_name, new_child):
110    """Replace child_name's old definition with new_child, in the context
111    of the given parent.  The parent could be a module when the child is a
112    function at module scope.  Or the parent could be a class when a class'
113    method is being replaced.  The named child is set to new_child, while
114    the prior definition is saved away for later, when UnsetAll() is called.
115
116    This method supports the case where child_name is a staticmethod or a
117    classmethod of parent.
118    """
119    old_child = getattr(parent, child_name)
120
121    old_attribute = parent.__dict__.get(child_name)
122    if old_attribute is not None and isinstance(old_attribute, staticmethod):
123      old_child = staticmethod(old_child)
124
125    self.cache.append((parent, old_child, child_name))
126    setattr(parent, child_name, new_child)
127
128  def UnsetAll(self):
129    """Reverses all the Set() calls, restoring things to their original
130    definition.  Its okay to call UnsetAll() repeatedly, as later calls have
131    no effect if no Set() calls have been made.
132
133    """
134    # Undo calls to Set() in reverse order, in case Set() was called on the
135    # same arguments repeatedly (want the original call to be last one undone)
136    self.cache.reverse()
137
138    for (parent, old_child, child_name) in self.cache:
139      setattr(parent, child_name, old_child)
140    self.cache = []