Move config.py to init/

Some simple changes needed to do that.

The interesting question left:
Should config_spec.ini also be moved?

mediagoblin/init/config.py

@@ -0,0 +1,122 @@
+# 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, flatten_errors
+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.
+
+    This function doesn't itself raise any exceptions if validation
+    fails, you'll have to do something
+
+    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 tuple like: (config, validation_result)
+      ... where 'conf' is the parsed config object and 'validation_result'
+      is the information from the validation process.
+    """
+    config_path = os.path.abspath(config_path)
+
+    config_spec = ConfigObj(
+        config_spec,
+        encoding='UTF8', list_values=False, _inspec=True)
+
+    _setup_defaults(config_spec, config_path)
+
+    config = ConfigObj(
+        config_path,
+        configspec=config_spec,
+        interpolation='ConfigParser')
+
+    _setup_defaults(config, config_path)
+
+    # For now the validator just works with the default functions,
+    # but in the future if we want to add additional validation/configuration
+    # functions we'd add them to validator.functions here.
+    # 
+    # See also:
+    #   http://www.voidspace.org.uk/python/validate.html#adding-functions
+    validator = Validator()
+    validation_result = config.validate(validator, preserve_errors=True)
+
+    return config, validation_result
+
+
+REPORT_HEADER = u"""\
+There were validation problems loading this config file:
+--------------------------------------------------------
+"""
+
+
+def generate_validation_report(config, validation_result):
+    """
+    Generate a report if necessary of problems while validating.
+
+    Returns:
+      Either a string describing for a user the problems validating
+      this config or None if there are no problems.
+    """
+    report = []
+
+    # Organize the report
+    for entry in flatten_errors(config, validation_result):
+        # each entry is a tuple
+        section_list, key, error = entry
+
+        if key is not None:
+            section_list.append(key)
+        else:
+            section_list.append(u'[missing section]')
+
+        section_string = u':'.join(section_list)
+
+        if error == False:
+            # We don't care about missing values for now.
+            continue
+
+        report.append(u"%s = %s" % (section_string, error))
+
+    if report:
+        return REPORT_HEADER + u"\n".join(report)
+    else:
+        return None