validation.py 文件源码

def check_field_spec(self, cls, model, flds, label):
        """
        Validate the fields specification in `flds` from a ModelAdmin subclass
        `cls` for the `model` model. Use `label` for reporting problems to the user.

        The fields specification can be a ``fields`` option or a ``fields``
        sub-option from a ``fieldsets`` option component.
        """
        for fields in flds:
            # The entry in fields might be a tuple. If it is a standalone
            # field, make it into a tuple to make processing easier.
            if type(fields) != tuple:
                fields = (fields,)
            for field in fields:
                if field in cls.readonly_fields:
                    # Stuff can be put in fields that isn't actually a
                    # model field if it's in readonly_fields,
                    # readonly_fields will handle the validation of such
                    # things.
                    continue
                try:
                    f = model._meta.get_field(field)
                except models.FieldDoesNotExist:
                    # If we can't find a field on the model that matches, it could be an
                    # extra field on the form; nothing to check so move on to the next field.
                    continue
                if isinstance(f, models.ManyToManyField) and not f.rel.through._meta.auto_created:
                    raise ImproperlyConfigured("'%s.%s' "
                        "can't include the ManyToManyField field '%s' because "
                        "'%s' manually specifies a 'through' model." % (
                            cls.__name__, label, field, field))