Incoming query params without value are modified

[wabiloo]

Describe the bug

I am working with a remote service that expects (among other things) a query parameter without value, eg "&bla".
However when going through the reverse proxy, the call made adds an = sign, which renders the call invalid for that remote service (over which I have no control)

To Reproduce

1. create a file main.py

from fastapi_proxy_lib.core.http import ReverseHttpProxy
from httpx import AsyncClient
from starlette.requests import Request
import logging 

logging.basicConfig(level=logging.DEBUG)

proxy = ReverseHttpProxy(AsyncClient(), base_url="https://www.httpbin.org/")

app = FastAPI()

@app.get("/get")
async def get(request: Request):
    return await proxy.proxy(request=request, path="get")

2. Run with uvicorn main:app --host 127.0.0.1 --port 8000
3. Call http://127.0.01:8000/get?bla
4. Notice in the logs that the call is made to https://www.httpbin.org/get?bla=, instead of https://www.httpbin.org/get?bla

Expected behavior

Query parameters should remain unchanged, even if they have no value

Configuration

• Python version: 13
• OS version: MacOS 15.5
• deps version:
  annotated-types==0.7.0
  anyio==4.6.2.post1
  Brotli==1.1.0
  certifi==2024.8.30
  charset-normalizer==3.4.0
  click==8.1.7
  dnspython==2.7.0
  email_validator==2.2.0
  fastapi==0.111.1
  fastapi-cli==0.0.5
  fastapi-proxy-lib==0.3.0
  h11==0.14.0
  httpcore==1.0.6
  httptools==0.6.4
  httpx==0.27.2
  httpx-ws==0.7.2
  idna==3.10
  Jinja2==3.1.4
  loguru==0.7.2
  markdown-it-py==3.0.0
  MarkupSafe==3.0.2
  mdurl==0.1.2
  pydantic==2.9.2
  pydantic_core==2.23.4
  Pygments==2.18.0
  python-dotenv==1.0.1
  python-multipart==0.0.17
  PyYAML==6.0.2
  requests==2.32.3
  rich==13.9.4
  shellingham==1.5.4
  sniffio==1.3.1
  starlette==0.37.2
  typer==0.13.0
  typing_extensions==4.12.2
  urllib3==2.2.3
  uvicorn==0.29.0
  uvloop==0.21.0
  watchfiles==0.24.0
  websockets==13.1
  wsproto==1.2.0

[wabiloo]

I believe the issue comes from the way the request is built, through the use of query_params

proxy_request = client.build_request(
            method=request.method,
            url=target_url,
            params=tuple(request.query_params.multi_items()),
            headers=proxy_header,
            content=request_content,  # FIXME: 一个已知问题是，流式响应头包含'transfer-encoding': 'chunked'，但有些服务器会400拒绝这个头
            # cookies=request.cookies,  # NOTE: headers中已有的cookie优先级高，所以这里不需要
        )

[WSH032]

Hi @wabiloo, thank you for reporting this. I would say the current behavior is expected.

The use of &bla as a query parameter is ambiguous. Different frameworks may interpret it differently: as {"bla": ""}, {"bla": None}, or {"bla": True}.
fastapi interprets it as {"bla": ""}. I'm not sure how your "remote service" interprets it.

We can't improve this situation because fastapi cannot distinguish between &bla and &bla=. For your specific case, you may need to use:

• https://wsh032.github.io/fastapi-proxy-lib/Usage/Advanced/#modify-request
• https://www.python-httpx.org/advanced/authentication/#custom-authentication-schemes

You might need to manually construct the URL, since as far as I know, using httpx.Request.params will not generate a URL like https://www.httpbin.org/get?bla (without the =).

Alternatively, you could contact the remote service and ask them to handle this case more flexibly.