mediagoblin/init/config.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011, 2012 MediaGoblin contributors.  See AUTHORS.
   3 #
   4 # This program is free software: you can redistribute it and/or modify
   5 # it under the terms of the GNU Affero General Public License as published by
   6 # the Free Software Foundation, either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Affero General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Affero General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 import copy
  18 import logging
  19 import os
  20 import pkg_resources
  21
  22 from configobj import ConfigObj, flatten_errors
  23 from validate import Validator
  24
  25
  26 _log = logging.getLogger(__name__)
  27
  28
  29 CONFIG_SPEC_PATH = pkg_resources.resource_filename(
  30     'mediagoblin', 'config_spec.ini')
  31
  32
  33 def _setup_defaults(config, config_path, extra_defaults=None):
  34     """
  35     Setup DEFAULTS in a config object from an (absolute) config_path.
  36     """
  37     extra_defaults = extra_defaults or {}
  38
  39     config.setdefault('DEFAULT', {})
  40     config['DEFAULT']['here'] = os.path.dirname(config_path)
  41     config['DEFAULT']['__file__'] = config_path
  42
  43     for key, value in extra_defaults.items():
  44         config['DEFAULT'].setdefault(key, value)
  45
  46
  47 def read_mediagoblin_config(config_path, config_spec_path=CONFIG_SPEC_PATH):
  48     """
  49     Read a config object from config_path.
  50
  51     Does automatic value transformation based on the config_spec.
  52     Also provides %(__file__)s and %(here)s values of this file and
  53     its directory respectively similar to paste deploy.
  54
  55     Also reads for [plugins] section, appends all config_spec.ini
  56     files from said plugins into the general config_spec specification.
  57
  58     This function doesn't itself raise any exceptions if validation
  59     fails, you'll have to do something
  60
  61     Args:
  62      - config_path: path to the config file
  63      - config_spec_path: config file that provides defaults and value types
  64        for validation / conversion.  Defaults to mediagoblin/config_spec.ini
  65
  66     Returns:
  67       A tuple like: (config, validation_result)
  68       ... where 'conf' is the parsed config object and 'validation_result'
  69       is the information from the validation process.
  70     """
  71     config_path = os.path.abspath(config_path)
  72
  73     # PRE-READ of config file.  This allows us to fetch the plugins so
  74     # we can add their plugin specs to the general config_spec.
  75     config = ConfigObj(
  76         config_path,
  77         interpolation="ConfigParser")
  78
  79     # temporary bootstrap, just setup here and __file__... we'll do this again
  80     _setup_defaults(config, config_path)
  81
  82     # Now load the main config spec
  83     config_spec = ConfigObj(
  84         config_spec_path,
  85         encoding="UTF8", list_values=False, _inspec=True)
  86
  87     # Set up extra defaults that will be pushed into the rest of the
  88     # configs.  This is a combined extrapolation of defaults based on
  89     mainconfig_defaults = copy.copy(config_spec.get("DEFAULT", {}))
  90     mainconfig_defaults.update(config["DEFAULT"])
  91
  92     plugins = config.get("plugins", {}).keys()
  93     plugin_configs = {}
  94
  95     for plugin in plugins:
  96         try:
  97             plugin_config_spec_path = pkg_resources.resource_filename(
  98                 plugin, "config_spec.ini")
  99             if not os.path.exists(plugin_config_spec_path):
 100                 continue
 101
 102             plugin_config_spec = ConfigObj(
 103                 plugin_config_spec_path,
 104                 encoding="UTF8", list_values=False, _inspec=True)
 105             _setup_defaults(
 106                 plugin_config_spec, config_path, mainconfig_defaults)
 107
 108             if not "plugin_spec" in plugin_config_spec:
 109                 continue
 110
 111             plugin_configs[plugin] = plugin_config_spec["plugin_spec"]
 112
 113         except ImportError:
 114             _log.warning(
 115                 "When setting up config section, could not import '%s'" %
 116                 plugin)
 117
 118     # append the plugin specific sections of the config spec
 119     config_spec["plugins"] = plugin_configs
 120
 121     _setup_defaults(config_spec, config_path, mainconfig_defaults)
 122
 123     config = ConfigObj(
 124         config_path,
 125         configspec=config_spec,
 126         interpolation="ConfigParser")
 127
 128     _setup_defaults(config, config_path, mainconfig_defaults)
 129
 130     # For now the validator just works with the default functions,
 131     # but in the future if we want to add additional validation/configuration
 132     # functions we'd add them to validator.functions here.
 133     #
 134     # See also:
 135     #   http://www.voidspace.org.uk/python/validate.html#adding-functions
 136     validator = Validator()
 137     validation_result = config.validate(validator, preserve_errors=True)
 138
 139     return config, validation_result
 140
 141
 142 REPORT_HEADER = u"""\
 143 There were validation problems loading this config file:
 144 --------------------------------------------------------
 145 """
 146
 147
 148 def generate_validation_report(config, validation_result):
 149     """
 150     Generate a report if necessary of problems while validating.
 151
 152     Returns:
 153       Either a string describing for a user the problems validating
 154       this config or None if there are no problems.
 155     """
 156     report = []
 157
 158     # Organize the report
 159     for entry in flatten_errors(config, validation_result):
 160         # each entry is a tuple
 161         section_list, key, error = entry
 162
 163         if key is not None:
 164             section_list.append(key)
 165         else:
 166             section_list.append(u'[missing section]')
 167
 168         section_string = u':'.join(section_list)
 169
 170         if error == False:
 171             # We don't care about missing values for now.
 172             continue
 173
 174         report.append(u"%s = %s" % (section_string, error))
 175
 176     if report:
 177         return REPORT_HEADER + u"\n".join(report)
 178     else:
 179         return None