Add `casbin-fastapi-decorator` to documentation as a community FastAPI integration

[Neko1313]

I've developed a small library called casbin-fastapi-decorator that provides a clean, decorator-based approach for integrating Casbin authorization into FastAPI projects.

The library was originally based on patterns developed during production use and has since been generalized to fit a wide range of FastAPI architectures. It supports pluggable user providers, enforcer providers, and error factories — making it adaptable without modifying the core integration code.

Links:

• Repository: https://github.com/Neko1313/casbin-fastapi-decorator
• PyPI: https://pypi.org/project/casbin-fastapi-decorator/

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Core usage

1. Define your guard once:

# authz.py
from casbin import Enforcer
from fastapi import HTTPException
from casbin_fastapi_decorator import PermissionGuard

guard = PermissionGuard(
    user_provider=get_current_user,       # any FastAPI dependency
    enforcer_provider=lambda: Enforcer("model.conf", "policy.csv"),
    error_factory=lambda *_: HTTPException(403, "Forbidden"),
)

2. Protect routes with decorators:

@app.get("/articles")
@guard.require_permission(Resource.POST, Permission.READ)
async def list_posts() -> list[PostSchema]:
    ...

@app.get("/me")
@guard.auth_required()
async def me(user: Annotated[UserSchema, Depends(get_current_user)]) -> UserSchema:
    ...

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Available integrations

The ecosystem currently includes three packages:

Package	Description
casbin-fastapi-decorator	Core library — PermissionGuard with pluggable providers
casbin-fastapi-decorator-jwt	JWTUserProvider — decodes JWT and maps claims to a user model
casbin-fastapi-decorator-db	DatabaseEnforcerProvider — loads policies from a SQLAlchemy model on each request

JWT example:

from casbin_fastapi_decorator_jwt import JWTUserProvider

user_provider = JWTUserProvider(
    secret_key="secret",
    algorithm="HS256",
    user_model=UserSchema,
)

guard = PermissionGuard(
    user_provider=user_provider,
    enforcer_provider=get_enforcer,
    error_factory=lambda *_: HTTPException(403, "Forbidden"),
)

Database-backed policies (SQLAlchemy):

from casbin_fastapi_decorator_db import DatabaseEnforcerProvider

enforcer_provider = DatabaseEnforcerProvider(
    model_path="casbin/model.conf",
    session_factory=async_session,
    policy_model=Policy,
    policy_mapper=lambda p: (p.sub, p.obj, p.act),
)

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Working examples

The repository includes three ready-to-run examples:

• examples/core — minimal setup with file-based policies and Bearer token auth
• examples/core-jwt — JWT authentication via JWTUserProvider
• examples/core-db — DB-backed policies via DatabaseEnforcerProvider (SQLAlchemy + aiosqlite)

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I'd like to propose adding this to the official documentation as a community integration option for FastAPI users. Happy to provide any additional context if needed.