id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
15616	django.core.exceptions.ValidationError is poorly implemented and documented	tomevans223	nobody	"django.core.exceptions.ValidationError has a horrific interface. It's publicly accessible attributes differ depending upon how the object is created, as do the pre/post conditions for it's publicly accessible methods.

If constructed with a dictionary of error messages, then it gets an attribute 'message_dict'.
If constructed with a string, or a list of strings, then it gets an attribute 'messages'.
The documentation on Model.clean() talks about ValidationError, but does not mention this at all, and instructs the user to look at messages_dict. [1]

If constructed with a dictionary of error messages, then the method update_error_dict(self, error_dict) will happily accept error_dict=None - it checks for and handles this condition. If constructed with a string or list, then not supplying error_dict is an error.

This sort of inconsistent behaviour is hard to explain. At the least, this behaviour should be documented clearly, but ideally the interface should be consistent, regardless of how it is constructed.

[1] http://docs.djangoproject.com/en/dev/ref/models/instances/#django.db.models.Model.clean"	Cleanup/optimization	closed	Core (Other)	dev	Normal	needsinfo	validation validationerror		Design decision needed	0	0	0	0	0	0