Add stringification for permissions

[MarkusH]

I want to document the required permissions for an API endpoint as part of the OpenAPI schema. Since OpenAPI doesn't seem to provide a way to add the permissions (understandable, it's out of context) I'm adding the permissions to a view's description.

But in order to turn a list of permissions into a string, the permissions need to be stringifiable. So, let's say I set permission_classes = [Perm1 | Perm2, Perm3 & Perm4] I would like to get something like this out: "Perm1 or Perm2, Perm3 and Perm4".

The core I have right now is this:

def format_operant(operant, operator=None):
    """
    Take a DRF permission instance as operant and format it in a human readable way.

    The operator can be passed to reduce the amount of parentheses. That is, if
    the operator is the result of an an AND or OR or NOT operator and identical
    to the provided operator, no parenthses are added.
    """
    require_parentheses = True
    if operator is not None:
        if isinstance(operant, operator):
            require_parentheses = False

    if isinstance(operant, BasePermission):
        return str(operant)
    elif not isinstance(operant, NOT):
        return f"({operant})" if require_parentheses else str(operant)
    else:
        return str(operant)

class AND:
    def __str__(self):
        return f"{format_operant(self.op1, AND)} and {format_operant(self.op2, AND)}"
    ...

class OR:
    def __str__(self):
        return f"{format_operant(self.op1, OR)} or {format_operant(self.op2, OR)}"
    ...

class NOT:
    def __str__(self):
        return f"not {format_operant(self.op1, NOT)}"
    ...

class BasePermission(metaclass=BasePermissionMetaclass):
    def __str__(self):
        return self.__class__.__name__
    ...

Additionally, I have a custom Schema that extends the description:

class AutoSchema(DRFAutoSchema):
    def get_description(self, path, method):
        desc = super().get_description(path, method)
        perms = "\n".join(f"- {perm}" for perm in self.get_permissions())
        return f"{desc}\n\nPermissions (all of the following):\n{perms}".strip()

    def get_permissions(self):
        return self.view.get_permissions()

Looking at the Swagger UI, this looks like this:

What I'm proposing is to add the stringification of the AND, OR, NOT, and BasePermission. Adjusting the schema is not part of the proposal, as that is easily extendible. However ,monkey-patching the classes with __str__ is ugly and should be avoided if possible.