Source Code for Package SCons.compat

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 23   
 24  __doc__ = """ 
 25  SCons compatibility package for old Python versions 
 26   
 27  This subpackage holds modules that provide backwards-compatible 
 28  implementations of various things that we'd like to use in SCons but which 
 29  only show up in later versions of Python than the early, old version(s) 
 30  we still support. 
 31   
 32  Other code will not generally reference things in this package through 
 33  the SCons.compat namespace.  The modules included here add things to 
 34  the builtins namespace or the global module list so that the rest 
 35  of our code can use the objects and names imported here regardless of 
 36  Python version. 
 37   
 38  The rest of the things here will be in individual compatibility modules 
 39  that are either: 1) suitably modified copies of the future modules that 
 40  we want to use; or 2) backwards compatible re-implementations of the 
 41  specific portions of a future module's API that we want to use. 
 42   
 43  GENERAL WARNINGS:  Implementations of functions in the SCons.compat 
 44  modules are *NOT* guaranteed to be fully compliant with these functions in 
 45  later versions of Python.  We are only concerned with adding functionality 
 46  that we actually use in SCons, so be wary if you lift this code for 
 47  other uses.  (That said, making these more nearly the same as later, 
 48  official versions is still a desirable goal, we just don't need to be 
 49  obsessive about it.) 
 50   
 51  We name the compatibility modules with an initial '_scons_' (for example, 
 52  _scons_subprocess.py is our compatibility module for subprocess) so 
 53  that we can still try to import the real module name and fall back to 
 54  our compatibility module if we get an ImportError.  The import_as() 
 55  function defined below loads the module as the "real" name (without the 
 56  '_scons'), after which all of the "import {module}" statements in the 
 57  rest of our code will find our pre-loaded compatibility module. 
 58  """ 
 59   
 60  __revision__ = "src/engine/SCons/compat/__init__.py 72ae09dc35ac2626f8ff711d8c4b30b6138e08e3 2019-08-08 14:50:06 bdeegan" 
 61   
 62  import os 
 63  import sys 
 64  import importlib 
 65   
 66  PYPY = hasattr(sys, 'pypy_translation_info') 
 67   
 68   
 69 -def rename_module(new, old): 
 70      """ 
 71      Attempt to import the old module and load it under the new name. 
 72      Used for purely cosmetic name changes in Python 3.x. 
 73      """ 
 74      try: 
 75          sys.modules[new] = importlib.import_module(old) 
 76          return True 
 77      except ImportError: 
 78          return False 
 79   
 80   
 81  # TODO: FIXME 
 82  # In 3.x, 'pickle' automatically loads the fast version if available. 
 83  rename_module('pickle', 'cPickle') 
 84   
 85  # Default pickle protocol. Higher protocols are more efficient/featureful 
 86  # but incompatible with older Python versions. On Python 2.7 this is 2. 
 87  # Negative numbers choose the highest available protocol. 
 88  import pickle 
 89   
 90  # Was pickle.HIGHEST_PROTOCOL 
 91  # Changed to 2 so py3.5+'s pickle will be compatible with py2.7. 
 92  PICKLE_PROTOCOL = pickle.HIGHEST_PROTOCOL 
 93   
 94  # TODO: FIXME 
 95  # In 3.x, 'profile' automatically loads the fast version if available. 
 96  rename_module('profile', 'cProfile') 
 97   
 98  # TODO: FIXME 
 99  # Before Python 3.0, the 'queue' module was named 'Queue'. 
100  rename_module('queue', 'Queue') 
101   
102  # TODO: FIXME 
103  # Before Python 3.0, the 'winreg' module was named '_winreg' 
104  rename_module('winreg', '_winreg') 
105   
106  # Python 3 moved builtin intern() to sys package 
107  # To make porting easier, make intern always live 
108  # in sys package (for python 2.7.x) 
109  try: 
110      sys.intern 
111  except AttributeError: 
112      # We must be using python 2.7.x so monkey patch 
113      # intern into the sys package 
114      sys.intern = intern 
115   
116  # UserDict, UserList, UserString are in # collections for 3.x, 
117  # but standalone in 2.7.x. Monkey-patch into collections for 2.7. 
118  import collections 
119   
120  try: 
121      collections.UserDict 
122  except AttributeError: 
123      from UserDict import UserDict as _UserDict 
124      collections.UserDict = _UserDict 
125      del _UserDict 
126   
127  try: 
128      collections.UserList 
129  except AttributeError: 
130      from UserList import UserList as _UserList 
131      collections.UserList = _UserList 
132      del _UserList 
133   
134  try: 
135      collections.UserString 
136  except AttributeError: 
137      from UserString import UserString as _UserString 
138      collections.UserString = _UserString 
139      del _UserString 
140   
141   
142  import shutil 
143  try: 
144      shutil.SameFileError 
145  except AttributeError: 
146 -    class SameFileError(Exception): 
147          pass 
148   
149      shutil.SameFileError = SameFileError 
150   
151 -def with_metaclass(meta, *bases): 
152      """ 
153      Function from jinja2/_compat.py. License: BSD. 
154   
155      Use it like this:: 
156   
157          class BaseForm(object): 
158              pass 
159   
160          class FormType(type): 
161              pass 
162   
163          class Form(with_metaclass(FormType, BaseForm)): 
164              pass 
165   
166      This requires a bit of explanation: the basic idea is to make a 
167      dummy metaclass for one level of class instantiation that replaces 
168      itself with the actual metaclass.  Because of internal type checks 
169      we also need to make sure that we downgrade the custom metaclass 
170      for one level to something closer to type (that's why __call__ and 
171      __init__ comes back from type etc.). 
172   
173      This has the advantage over six.with_metaclass of not introducing 
174      dummy classes into the final MRO. 
175      """ 
176   
177      class metaclass(meta): 
178          __call__ = type.__call__ 
179          __init__ = type.__init__ 
180   
181          def __new__(cls, name, this_bases, d): 
182              if this_bases is None: 
183                  return type.__new__(cls, name, (), d) 
184              return meta(name, bases, d) 
185   
186      return metaclass('temporary_class', None, {}) 
187   
188   
189 -class NoSlotsPyPy(type): 
190      """ 
191      Workaround for PyPy not working well with __slots__ and __class__ assignment. 
192      """ 
193   
194 -    def __new__(meta, name, bases, dct): 
195          if PYPY and '__slots__' in dct: 
196              dct.pop('__slots__') 
197          return super(NoSlotsPyPy, meta).__new__(meta, name, bases, dct) 
198   
199  # Local Variables: 
200  # tab-width:4 
201  # indent-tabs-mode:nil 
202  # End: 
203  # vim: set expandtab tabstop=4 shiftwidth=4: 
204