Fixed AssertionError and unnecessary connect delay (nedbat#94)

If an earlier connection attempt succeeds, it should signal that the other attempts should be cancelled. This patch makes the first successful attempt cancel the entire scope immediately to achieve that effect.

Author: agronholm

anyio/__init__.py

@@ -347,9 +347,12 @@ async def try_connect(af: int, addr: str, event: Event):
             await sock.close()
             raise
         else:
-            assert stream is None
-            stream = _networking.SocketStream(sock, ssl_context, target_host,
-                                              tls_standard_compatible)
+            if stream is None:
+                stream = _networking.SocketStream(sock, ssl_context, target_host,
+                                                  tls_standard_compatible)
+                await tg.cancel_scope.cancel()
+            else:
+                raw_socket.close()
         finally:
             await event.set()
 
@@ -393,10 +396,6 @@ async def try_connect(af: int, addr: str, event: Event):
             async with move_on_after(happy_eyeballs_delay):
                 await event.wait()
 
-            if stream is not None:
-                await tg.cancel_scope.cancel()
-                break
-
     if stream is None:
         cause = oserrors[0] if len(oserrors) == 1 else asynclib.ExceptionGroup(oserrors)
         raise OSError('All connection attempts failed') from cause