Allow Responses to be used as Context Managers

Requests API allows Responses to be used and closed as a context manager.

We should allow the following use-cases:

async def run_async():
    client = httpx.AsyncClient()
    async with client.get("https://example.com") as resp:
        resp.raise_for_status()

def run_sync():
    client = httpx.Client()
    with client.get("https://example.com") as resp:
        resp.raise_for_status()

See: LoryCS/anido#1

I think this is a good thing beyond Requests compatibility — ensures that all resources are properly closed in case something goes wrong. I'm kind of growing the intuition that ideally we should be following trio's lessons and enforce (async) context manager usage everywhere — on clients, on responses, …

Okay, so...

This is relevant only for the streaming case.
In other cases the response has been closed by the point it's returned from the function.

There's a question here to be had in that client.get(..., stream=True) is actually fundamentally different to client.get(...) because you really want to be using a context manager for the first case.

Requests has exactly the same issue, and actually makes it really easy to not close streaming responses. One option that we could do here that's a bit radical would be to diverge from the requests API here, even through stream=True is a fairly widely used case.

Eg. client.stream() could return a context managed response. (It might have a default method='get' that could be overidden.)

One other bugbear to be wary of here is that "stream" in this context specifically means "stream the response", not "stream the request" (which yes, we support, but that's different), but the naming isn't very clear about the expectation.

I'd like to work on this.

Main question here is where we want to go with the API...

Add a .stream(method='GET') method which is always what we use for streaming cases, so that we can ensure that they're always context-manged.
Stay in line with requests and just use stream=True on the existing methods. Keeps the API the same, but really easy to fail to close a response, which isn't awful but will leave the connection hanging.

Maybe we can put a warning on the Responses garbage collector that it wasn't closed properly, similar to files?

Closing this. Evidentally outdated somewhere along the line - we do support responses as context managers. 👍

@tomchristie

@tomchristie Do we? The Response class doesn't implement __aenter__()/__aexit__(), so this might have been an oversight?

# client.py
import asyncio
import httpx

async def main():
    url = "http://localhost:8000"
    async with httpx.get(url) as resp:
        print(resp)

asyncio.run(main())

$ python debug/client.py
debug/client.py:8: RuntimeWarning: coroutine 'get' was never awaited
  async with httpx.get(url) as resp:
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
Traceback (most recent call last):
  File "debug/client.py", line 12, in <module>
    asyncio.run(main())
  File "/Users/florimond/.pyenv/versions/3.8.0/lib/python3.8/asyncio/runners.py", line 43, in run
    return loop.run_until_complete(main)
  File "/Users/florimond/.pyenv/versions/3.8.0/lib/python3.8/asyncio/base_events.py", line 608, in run_until_complete
    return future.result()
  File "debug/client.py", line 8, in main
    async with httpx.get(url) as resp:
AttributeError: __aexit__

Obsoleted by #600

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Allow Responses to be used as Context Managers #393

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Allow Responses to be used as Context Managers #393

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florimondmanca commented on Sep 27, 2019

lovelydinosaur commented on Sep 27, 2019

gdhameeja commented on Oct 3, 2019

lovelydinosaur commented on Oct 4, 2019

sethmlarson commented on Oct 4, 2019

lovelydinosaur commented on Nov 27, 2019

florimondmanca commented on Nov 29, 2019

lovelydinosaur commented on Dec 9, 2019

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