Issue 37404: asyncio sock_recv blocks on ssl sockets.

I'm working on a server that uses sock_recv from asyncio.
await sock_recv(socket, n) never returns if socket is wrapped in ssl using the wrap_socket function from the ssl module.
I think the problem stated in this stackoverflow question could be the reason: https://stackoverflow.com/questions/40346619/behavior-of-pythons-select-with-partial-recv-on-ssl-socket

You can't use sock_recv() with a wrapped SSL socket. A SSLSocket behaves differently because there is user-level buffering. The connection operates on TLS frames and only hands off data after it has been decrypted and verified. asyncio uses wrap_bio().

Can you please elaborate on how to get around this issue?

Use asyncio transports or streams.
sock_recv() is a low-level API with a very limited audience.

wrapped ssl socket provides a synchronous interface only.

Perhaps we should raise an exception if SSLSocket is passed into asyncio functions.

Ah, I see. Yes, raising an exception would probably be very useful. Thanks for the info.

Fixed this issue since the CLA of the past user wasn't signed.

Added a check for the socket type in each of the methods: 
sock_recv, sock_recv_into, sock_sendall, sock_connect, sock_accept.

PR: GH-16457

New changeset 892f9e0777f262d366d4747a54c33a1c15a49da6 by Miss Islington (bot) (idomic) in branch 'master':
 bpo-37404: Raising value error if an SSLSocket is passed to asyncio functions (GH-16457)
https://github.com/python/cpython/commit/892f9e0777f262d366d4747a54c33a1c15a49da6

New changeset 930cef2770b641f49e69b67840daaa53b65cd0e0 by Andrew Svetlov in branch '3.8':
[3.8] bpo-37404: Raising value error if an SSLSocket is passed to asyncio functions (GH-16457) (#17496)
https://github.com/python/cpython/commit/930cef2770b641f49e69b67840daaa53b65cd0e0

New changeset a85066df9423d381e6b233469b00db55563a9f80 by Miss Islington (bot) in branch '3.7':
bpo-37404: Raising value error if an SSLSocket is passed to asyncio functions (GH-16457)
https://github.com/python/cpython/commit/a85066df9423d381e6b233469b00db55563a9f80

The patch broke Python builds without ssl support and caused a minor performance regression in hot paths. I changed the code to only perform the check in debug mode.

Sorry it broke the version, what could I have done to avoid this?
Also can we close this issue?

stage: resolved -> patch review