mdw@git.distorted.org.uk Git - chopwood/blob - config.py

   1 ### -*-python-*-
   2 ###
   3 ### Configuration handling
   4 ###
   5 ### (c) 2013 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This file is part of Chopwood: a password-changing service.
  11 ###
  12 ### Chopwood is free software; you can redistribute it and/or modify
  13 ### it under the terms of the GNU Affero General Public License as
  14 ### published by the Free Software Foundation; either version 3 of the
  15 ### License, or (at your option) any later version.
  16 ###
  17 ### Chopwood is distributed in the hope that it will be useful,
  18 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ### GNU Affero General Public License for more details.
  21 ###
  22 ### You should have received a copy of the GNU Affero General Public
  23 ### License along with Chopwood; if not, see
  24 ### <http://www.gnu.org/licenses/>.
  25
  26 from __future__ import with_statement
  27
  28 import os as OS; ENV = OS.environ
  29 import sys as SYS
  30 import types as TY
  31
  32 from auto import PACKAGE, VERSION
  33
  34 ### Configuration is done by interpreting a file of Python code.  We expect
  35 ### the code to define a number of variables in its global scope.  We import
  36 ### a number of identifiers (named in the `EXPORT' list) to this module, and
  37 ### also our entire parent module as `chpwd'.
  38
  39 ## Names which ought to be exported to the configuration module.
  40 _EXPORT = {}
  41
  42 ## The configuration module.
  43 CFG = TY.ModuleType('chpwd_config')
  44
  45 ## A list of hooks to call once configuration is complete.
  46 _HOOKS = []
  47 def hook(func):
  48   """Decorator for post-configuration hooks."""
  49   _HOOKS.append(func)
  50   return func
  51
  52 ## A suitable set of defaults.
  53 DEFAULTS = {}
  54
  55 def export(*names, **kw):
  56   """
  57   Export the names to the configuration module from the caller's environment.
  58   """
  59
  60   ## Find the caller's global environment.  Please don't try this at home.
  61   try: raise Exception
  62   except: tb = SYS.exc_info()[2]
  63   env = tb.tb_frame.f_back.f_globals
  64
  65   ## Export things.
  66   for name in names:
  67     _EXPORT[name] = env[name]
  68   _EXPORT.update(kw)
  69
  70 ## Some things to export for sure.
  71 export('PACKAGE', 'VERSION', 'ENV', CONF = SYS.modules[__name__])
  72
  73 def loadconfig(config):
  74   """
  75   Load the configuration, populating the `CFG' module with settings.
  76   """
  77
  78   ## Make a new module for the configuration, and import ourselves into it.
  79   d = CFG.__dict__
  80   d.update(_EXPORT)
  81   d.update(DEFAULTS)
  82
  83   ## And run the configuration code.
  84   with open(config) as f:
  85     exec f in d
  86
  87   ## Run the hooks.
  88   for func in _HOOKS:
  89     func()
  90
  91 ###----- That's all, folks --------------------------------------------------