Modifying "response" event hooks affects "in-flight" requests too.

[T0rvadaL]

As it says in the title. This obviously only affects the AsyncClient.

I'm not sure if this is considered an issue, but the problem lies in this code snipped in the _send_handling_redirects method:

for hook in self._event_hooks["request"]:
                await hook(request)

            response = await self._send_single_request(request)  # from here
            try:
                for hook in self._event_hooks["response"]:
                    await hook(response)                         # to here

                response.history = list(history)

                if not response.has_redirect_location:
                    return response

                request = self._build_redirect_request(request, response)
                history = history + [response]

                if follow_redirects:
                    await response.aread()
                else:
                    response.next_request = request
                    return response

            except BaseException as exc:
                await response.aclose()
                raise exc

As you can see, it uses the current value of the _event_hooks property, which might have changed while the request was in-flight.

Here is a failing unit test for good measure:

import httpx
import pytest


@pytest.mark.asyncio
async def test_response_hooks_do_not_affect_incoming_responses():
    async def hook(response):
        response.status_code = 9000

    def mock_response(request):
        client.event_hooks["response"] = [hook]
        return httpx.Response(200)

    transport = httpx.MockTransport(mock_response)
    client = httpx.AsyncClient(transport=transport)
    response = await client.get("https://testy.cl")
    assert response.status_code == 200