Custom Decorators

Austial is built around a single mechanism — a metadata bag attached to every decorated class or function (austial.core.metadata.set_metadata / get_metadata). Every framework decorator (@Module, @Controller, the route decorators, @UseGuards, @Injectable, …) is built on top of it, and it’s directly available to you for your own decorators, guards, and interceptors.

set_metadata / get_metadata

from austial.core.metadata import get_metadata, set_metadata
 
ROLES_KEY = "roles"
 
 
def Roles(*roles: str):
    def decorator(target):
        set_metadata(ROLES_KEY, list(roles), target)
        return target
 
    return decorator

@Controller("cats")
class CatsController:
    @Get()
    @Roles("admin", "moderator")
    async def find_all(self):
        ...

This is a decorator factory that stamps metadata onto whatever it’s applied to (class or method).

Reading metadata with Reflector

austial.core.reflector.Reflector is the read-side counterpart, injectable anywhere the container resolves dependencies — most commonly inside a guard:

from austial import CanActivate, ExecutionContext
from austial.core.reflector import Reflector
 
from .roles_decorator import ROLES_KEY
 
 
class RolesGuard(CanActivate):
    def __init__(self, reflector: Reflector):
        self._reflector = reflector
 
    async def can_activate(self, context: ExecutionContext) -> bool:
        required_roles = self._reflector.get(ROLES_KEY, context.get_handler())
        if not required_roles:
            return True   # no @Roles(...) on this handler -> no restriction
 
        request = context.get_request()
        user_roles = request.headers.get("x-roles", "").split(",")
        return any(role in user_roles for role in required_roles)

@Get()
@Roles("admin")
@UseGuards(RolesGuard)
async def find_all(self):
    ...

Reflector also exposes get_all_and_merge/get_all_and_override for reading the same metadata key stamped at both the controller and handler level and combining them.

Where this is used internally

Every @Use* decorator (@UseGuards, @UsePipes, @UseInterceptors, @UseFilters), @HttpCode, @Header, and @Catch are themselves thin wrappers around set_metadata/get_metadata with a dedicated key (GUARDS_METADATA, PIPES_METADATA, INTERCEPTORS_METADATA, FILTERS_METADATA, CATCH_METADATA in austial/core/metadata.py) — so a custom decorator you write with the same primitives is a first-class citizen, not a workaround.