`params` overrides query string in url

[j178]

Hi,

I noticed a difference between httpx and requests when processing query parameters. I provided the params for the url with query string, requests would merge params into query string, but httpx replaces the whole query string.

Here is a simple script:

import requests
import httpx
import asyncio

URL = 'https://httpbin.org/get?a=1'

r = requests.get(URL, params={'b': 2})
print('requests', r.json()['args'])

async def f():
    r = await httpx.get(URL, params={'b': 2})
    print('httpx', r.json()['args'])
asyncio.run(f())

Results:

requests {'a': '1', 'b': '2'}
httpx {'b': '2'}

Is this an intended behavior?

[lovelydinosaur]

Not intentional, nope.

It looks like we need to make sure the merge_queryparams also accepts the url, and includes any query params that are included there.

https://github.com/encode/httpx/blob/master/httpx/client.py#L370-L381

[lovelydinosaur]

On second thoughts, we should actually be handling that bit on the URL class itself.

(So that manually building a request with request = Request(url, params=params) has the right merge behavior too.)

The signature there is URL(url, params=None). When params are provided they remove any querystring on the url, and replace it with params. Instead we should merge any params argument with any query params that are present in the URL string.