indico/util/patches.py

   1 # This file is part of Indico.
   2 # Copyright (C) 2002 - 2015 European Organization for Nuclear Research (CERN).
   3 #
   4 # Indico is free software; you can redistribute it and/or
   5 # modify it under the terms of the GNU General Public License as
   6 # published by the Free Software Foundation; either version 3 of the
   7 # License, or (at your option) any later version.
   8 #
   9 # Indico is distributed in the hope that it will be useful, but
  10 # WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 # General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU General Public License
  15 # along with Indico; if not, see <http://www.gnu.org/licenses/>.
  16
  17 """
  18 Some "monkey patches" for old Python versions
  19 """
  20
  21 from __future__ import absolute_import
  22
  23 import sys
  24 import re
  25 import operator as ops
  26
  27
  28 VERSION_RE = re.compile(r'(>=|>|<|<=)?(\d)(?:\.(\d))?')
  29 PATCHES = []
  30
  31
  32 def _version_data(ver):
  33     m = VERSION_RE.match(ver)
  34     if m:
  35         m = m.groups()
  36         return m[0], int(m[1]), int(m[2])
  37     else:
  38         raise Exception("Wrong version specification: '{0}'".format(ver))
  39
  40
  41 def _version_matches(my_ver, op, rule_ver):
  42
  43     return {
  44         None: ops.eq,
  45         '>': ops.gt,
  46         '<': ops.lt,
  47         '>=': ops.ge,
  48         '<=': ops.le
  49     }[op](my_ver, rule_ver)
  50
  51
  52 def version(ver):
  53     def wrapper(f):
  54         version_data = _version_data(ver)
  55         PATCHES.append((version_data, f))
  56     return wrapper
  57
  58
  59 def always(f):
  60     PATCHES.append((None, f))
  61
  62
  63 @always
  64 def redis_pipeline_nonzero():
  65     """
  66     py-redis added a __len__ method to its BasePipeline class recently.
  67     For our magic to work we need redis objects to be always considered
  68     nonzero - no matter if it's a redis client or a redis pipeline.
  69     """
  70     try:
  71         import redis.client
  72     except ImportError:
  73         pass
  74     else:
  75         redis.client.BasePipeline.__nonzero__ = lambda self: True
  76
  77
  78 def apply_patches():
  79     for version_data, func in PATCHES:
  80         if version_data is not None:
  81             op, maj, minor = version_data
  82             if not _version_matches((maj, minor), op, sys.version_info[:2]):
  83                 continue
  84         func()