Duplicate options are allowed in sections of trac.ini

[Ryan J Ollos]

The sections of trac.ini allow duplicate options, with later values overwriting those that come first. Two patterns that could lead to confusing behavior when the user doesn't realize that the option's value is being changed later in the file are:

1. Duplicate sections with the same option.

   [trac]
   default_handler = WikiModule
   
   ...
   
   [trac]
   default_handler = TicketModule
   

2. Duplicate options within a section.

   [trac]
   default_handler = WikiModule
   
   ...
   
   default_handler = TicketModule
   

While Python 3.x has a much improved ​configparser module with a strict mode that raises an error when an option appears more than once, I'm not sure there is much we can do in Python 2.x using ConfigParser.

​SO:5396653 suggests using a dict_type that allows multiple values with the same key, however dict_type is only supported in Python 2.6, so we wouldn't be able to apply as dict_type-based fix to 1.0-stable.

[Ryan J Ollos]

After #11982, which replaced use of ConfigObj with ConfigParser, an exception is no longer raised when there is a duplicate section or option in an authz_policy configuration file. One test is commented out: trunk/tracopt/perm/tests/authz_policy.py@13994:223-234#L223​.

[Ryan J Ollos]

See [97e3bdb2/rjollos.git].

[Ryan J Ollos]

I think this could avoid some difficult to find problems. Examples:

Internal Server Error

TracError: DuplicateSectionError: While reading from '/Users/rjollos/Documents/Workspace/trac-dev/tracenvs/proj-1.5/conf/trac.ini' [line  8]: section 'attachment' already exists

Internal Server Error

TracError: DuplicateOptionError: While reading from '/Users/rjollos/Documents/Workspace/trac-dev/tracenvs/proj-1.5/conf/trac.ini' [line 39]: option 'acct_mgr.register.*' in section 'components' already exists

Proposed changes in [00a4344992/rjollos.git]. Deferring to 1.5.3. Please let me know if you see any major problems with switching to strict parsing.

[Jun Omae]

I consider AuthzPolicy.parse_authz() should catch all Errors of configparser when parsing the file.

         self.authz = UnicodeConfigParser(ignorecase_option=False)
         try:
             self.authz.read(self.authz_file)
-        except ParsingError as e:
+        except configparser.Error as e:
             self.log.error("Error parsing authz permission policy file: %s",
                            exception_to_unicode(e))
-            raise ConfigurationError()
+            raise ConfigurationError(_("Error parsing authz permission policy "
+                                       "file: %(err)s",
+                                       err=exception_to_unicode(e)))

[Ryan J Ollos]

Catching all Errors is a good idea. Thanks.

When working on this module previously I intentionally didn't raise a message for ConfigurationError because it seemed like a possible security risk.

[Ryan J Ollos]

Also noticed #13335, which I'll fix on 1.4-stable.

[Ryan J Ollos]

Committed to trunk in r17491.