FastAPI中如何为依赖函数传参且避免被识别为查询参数

问题根源：你之前用lambda作为Depends参数的写法里，lambda的request参数没有类型标注，FastAPI无法识别这是需要注入的Request对象，反而把lambda的参数当成了路由的查询参数，导致"some-argument"被错误解析成查询参数。

下面是几种可行的正确传参方式：

方案1：闭包包装依赖函数 #

通过外层函数接收固定参数，返回的内层函数专门处理Request注入并调用目标依赖：

from fastapi import Depends, Request, JSONResponse
from fastapi.routing import APIRouter

some_router = APIRouter()

async def do_something(request: Request, value: str):
    pass

def get_do_something(value: str):
    async def wrapper(request: Request):
        return await do_something(request, value)
    return wrapper

@some_router.post("/some-route") 
async def handleRoute(something = Depends(get_do_something("some-argument"))):     
    return JSONResponse(content={"msg": "Route"}, status_code=200)

方案2：用functools.partial绑定参数 #

借助functools.partial提前绑定固定参数，再通过辅助依赖函数接收Request：

from fastapi import Depends, Request, JSONResponse
from fastapi.routing import APIRouter
from functools import partial

some_router = APIRouter()

async def do_something(request: Request, value: str):
    pass

# 绑定固定参数
bound_do_something = partial(do_something, value="some-argument")

async def depend_do_something(request: Request):
    return await bound_do_something(request)

@some_router.post("/some-route") 
async def handleRoute(something = Depends(depend_do_something)):     
    return JSONResponse(content={"msg": "Route"}, status_code=200)

方案3：直接定义专用依赖函数 #

如果固定参数不需要动态调整，直接写一个专用依赖函数，内部调用时传入固定值：

from fastapi import Depends, Request, JSONResponse
from fastapi.routing import APIRouter

some_router = APIRouter()

async def do_something(request: Request, value: str):
    pass

async def depend_do_something(request: Request):
    return await do_something(request, "some-argument")

@some_router.post("/some-route") 
async def handleRoute(something = Depends(depend_do_something)):     
    return JSONResponse(content={"msg": "Route"}, status_code=200)

内容的提问来源于stack exchange，提问作者ILIKETOLEARN