bpo-40262: SSLSocket.recv_into() shouldn't require __len__

Lib/ssl.py

@@ -1230,7 +1230,7 @@ class SSLSocket(socket):
     def recv_into(self, buffer, nbytes=None, flags=0):
         self._checkClosed()
         if buffer and (nbytes is None):
-            nbytes = len(buffer)
+            nbytes = memoryview(buffer).nbytes
         elif nbytes is None:
             nbytes = 1024
         if self._sslobj is not None:

Lib/test/test_ssl.py

@@ -3607,6 +3607,22 @@ class ThreadedTests(unittest.TestCase):
         self.assertEqual(s.recv(0), b"")
         self.assertEqual(s.recv_into(bytearray()), 0)
 
+    def test_recv_into_buffer_protocol_len(self):
+        server = ThreadedEchoServer(CERTFILE)
+        server.__enter__()
+        self.addCleanup(server.__exit__, None, None)
+        s = socket.create_connection((HOST, server.port))
+        self.addCleanup(s.close)
+        s = test_wrap_socket(s, suppress_ragged_eofs=False)
+        self.addCleanup(s.close)
+
+        class B(bytearray):
+            def __len__(self):
+                return 1
+
+        s.send(b"data")
+        self.assertEqual(s.recv_into(B(4)), 4)
+
     def test_nonblocking_send(self):
         server = ThreadedEchoServer(CERTFILE,
                                     certreqs=ssl.CERT_NONE,

Misc/NEWS.d/next/Library/2020-05-21-23-32-46.bpo-40262.z4fQv1.rst

@@ -0,0 +1,2 @@
+The :meth:`ssl.SSLSocket.recv_into` method no longer requires the *buffer*
+argument to implement ``__len__``.