Extended model validation

extendedmodelvalidation.py

class ExtendedValidationModel(models.Model):
    """
    Abstract model class that adds conditional field cleaning/validation.

    You can create extended field validation with model methods like:

    def clean_<fieldname>(self):
        # things gone bad
            raise ValidationError('whatever')
        return self.<fieldname>

    To enable extended validation make sure you set
    <ModelInstance>.EXTENDED_VALIDATION = True
    befor calling <ModelInstance>.full_clean()
    """

    class Meta:
        abstract = True

    EXTENDED_VALIDATION = False

    def clean_fields(self, exclude):
        if exclude is None:
            exclude = []

        errors = {}
        try:
            super(ExtendedValidationModel, self).clean_fields(exclude)
        except ValidationError as e:
            errors = e.update_error_dict(errors)

        if self.EXTENDED_VALIDATION:
            for f in self._meta.fields:
                if f.name in exclude:
                    continue
                if hasattr(self, "clean_%s" % f.name):
                    try:
                        value = getattr(self, "clean_%s" % f.name)()
                        setattr(self, f.name, value)
                    except ValidationError as e:
                        errors = ValidationError({f.name: e.messages})\
                            .update_error_dict(errors)
        if errors:
            raise ValidationError(errors)