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 output as O; OUT = O.OUT
  30 import sys as SYS
  31 import types as TY
  32
  33 from auto import PACKAGE, VERSION
  34
  35 ### Configuration is done by interpreting a file of Python code.  We expect
  36 ### the code to define a number of variables in its global scope.  We import
  37 ### a number of identifiers (named in the `EXPORT' list) to this module, and
  38 ### also our entire parent module as `chpwd'.
  39
  40 ## Names which ought to be exported to the configuration module.
  41 _EXPORT = {}
  42
  43 ## The configuration module.
  44 CFG = TY.ModuleType('chpwd_config')
  45
  46 ## A list of hooks to call once configuration is complete.
  47 _HOOKS = []
  48 def hook(func):
  49   """Decorator for post-configuration hooks."""
  50   _HOOKS.append(func)
  51   return func
  52
  53 ## A suitable set of defaults.
  54 DEFAULTS = {}
  55
  56 def export(*names, **kw):
  57   """
  58   Export the names to the configuration module from the caller's environment.
  59   """
  60
  61   ## Find the caller's global environment.  Please don't try this at home.
  62   try: raise Exception
  63   except: tb = SYS.exc_info()[2]
  64   env = tb.tb_frame.f_back.f_globals
  65
  66   ## Export things.
  67   for name in names:
  68     _EXPORT[name] = env[name]
  69   _EXPORT.update(kw)
  70
  71 ## Some things to export for sure.
  72 export('PACKAGE', 'VERSION', 'ENV', CONF = SYS.modules[__name__])
  73
  74 def loadconfig(config):
  75   """
  76   Load the configuration, populating the `CFG' module with settings.
  77   """
  78
  79   ## Make a new module for the configuration, and import ourselves into it.
  80   d = CFG.__dict__
  81   d.update(_EXPORT)
  82   d.update(DEFAULTS)
  83
  84   ## And run the configuration code.
  85   try:
  86     with open(config) as f:
  87       exec f in d
  88   except IOError, e:
  89     OUT.warn("couldn't open configuration file `%s': %s" %
  90              (config, e.strerror))
  91
  92   ## Run the hooks.
  93   for func in _HOOKS:
  94     func()
  95
  96 ###----- That's all, folks --------------------------------------------------