AsyncClient requires content to be async iterable *and not* sync iterable

[jakkdl]

Related to #1620, but not fixed by #3339

Async streaming requests somewhat sensible requires async bytes generators, but it will error if the streaming content is a sync generator and async generator. This makes no sense, and is a hassle as it requires a wrapper that hides the sync interface for httpx to accept it https://github.com/aio-libs/aiobotocore/blob/fe5ee7c7169783514f2b15fb8098fba97ccf3f65/aiobotocore/httpxsession.py#L194-L208

repro:

import asyncio
import httpx

class SyncAsyncIterable:
    def __init__(self, data):
        self.data = data

    def __iter__(self):
        yield from self.data

    def __aiter__(self):
        return self

    async def __anext__(self):
        for chunk in self.data:
            yield chunk
        raise StopAsyncIteration


async def test_request():
    content = SyncAsyncIterable([b"hello", b" ", b"world"])

    async with httpx.AsyncClient() as client:
        await client.post("https://httpbin.org/post", content=content)

if __name__ == "__main__":
    asyncio.run(test_request())

...
  File "/home/h/Git/aiobotocore/test_shit/httpx_repro.py", line 28, in test_request
    response = await client.post("https://httpbin.org/post", content=content)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/h/Git/aiobotocore/test_shit/.venv/lib/python3.13/site-packages/httpx/_client.py", line 1859, in post
    return await self.request(
           ^^^^^^^^^^^^^^^^^^^
    ...<13 lines>...
    )
    ^
  File "/home/h/Git/aiobotocore/test_shit/.venv/lib/python3.13/site-packages/httpx/_client.py", line 1540, in request
    return await self.send(request, auth=auth, follow_redirects=follow_redirects)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/h/Git/aiobotocore/test_shit/.venv/lib/python3.13/site-packages/httpx/_client.py", line 1629, in send
    response = await self._send_handling_auth(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<4 lines>...
    )
    ^
  File "/home/h/Git/aiobotocore/test_shit/.venv/lib/python3.13/site-packages/httpx/_client.py", line 1657, in _send_handling_auth
    response = await self._send_handling_redirects(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<3 lines>...
    )
    ^
  File "/home/h/Git/aiobotocore/test_shit/.venv/lib/python3.13/site-packages/httpx/_client.py", line 1694, in _send_handling_redirects
    response = await self._send_single_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/h/Git/aiobotocore/test_shit/.venv/lib/python3.13/site-packages/httpx/_client.py", line 1725, in _send_single_request
    raise RuntimeError(
        "Attempted to send an sync request with an AsyncClient instance."
    )
RuntimeError: Attempted to send an sync request with an AsyncClient instance.

[lovelydinosaur]

but it will error if the streaming content is a sync generator and async generator.

Is that true?

httpx/httpx/_client.py

Lines 1724 to 1727 in 6c7af96

	if not isinstance(request.stream, AsyncByteStream):
	raise RuntimeError(
	"Attempted to send a sync request with an AsyncClient instance."
	)

[jakkdl]

yes, because at that point the sync+async generator has been transformed into a IteratorByteStream that has "destroyed" the async-ness. I think I tracked down the specific logic at some point but don't remember anymore, but there's some overeager conversion going on earlier in the process

[lovelydinosaur]

Ah yep...

httpx/httpx/_content.py

Line 210 in 6c7af96

return encode_content(content)