Configuration file loading via ConfigObj.

Uses ConfigObj to open the config file.  Also does validation via the
config spec, so defaults are provided, strings are interpolated, types
are converted.

mediagoblin/config.py

@@ -0,0 +1,71 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2011 Free Software Foundation, Inc
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import pkg_resources
+
+from configobj import ConfigObj
+from validate import Validator
+
+
+CONFIG_SPEC_PATH = pkg_resources.resource_filename(
+    'mediagoblin', 'config_spec.ini')
+
+
+def _setup_defaults(config, config_path):
+    """
+    Setup DEFAULTS in a config object from an (absolute) config_path.
+    """
+    config.setdefault('DEFAULT', {})
+    config['DEFAULT']['here'] = os.path.dirname(config_path)
+    config['DEFAULT']['__file__'] = config_path
+
+
+def read_mediagoblin_config(config_path, config_spec=CONFIG_SPEC_PATH):
+    """
+    Read a config object from config_path.
+
+    Does automatic value transformation based on the config_spec.
+    Also provides %(__file__)s and %(here)s values of this file and
+    its directory respectively similar to paste deploy.
+
+    Args:
+     - config_path: path to the config file
+     - config_spec: config file that provides defaults and value types
+       for validation / conversion.  Defaults to mediagoblin/config_spec.ini
+
+    Returns:
+      A read ConfigObj object.
+    """
+    config_path = os.path.abspath(config_path)
+
+    config_spec = ConfigObj(
+        CONFIG_SPEC_PATH,
+        encoding='UTF8', list_values=False, _inspec=True)
+
+    _setup_defaults(config_spec, config_path)
+
+    conf = ConfigObj(
+        config_path,
+        configspec=config_spec,
+        interpolation='ConfigParser')
+
+    _setup_defaults(conf, config_path)
+
+    conf.validate(Validator())
+
+    return conf
+