Replacing assignation by typing for websocket_handshake (#2273)

* Replacing assignation by typing for `websocket_handshake`

Related to #2272

* Fix some type hinting issues

* Cleanup websocket handchake response concat

* Optimize concat encoding

Co-authored-by: Adam Hopkins <adam@amhopkins.com>

sanic/server/protocols/websocket_protocol.py

@@ -1,7 +1,8 @@
-from typing import TYPE_CHECKING, Optional, Sequence
+from typing import TYPE_CHECKING, Optional, Sequence, cast
 
 from websockets.connection import CLOSED, CLOSING, OPEN
 from websockets.server import ServerConnection
+from websockets.typing import Subprotocol
 
 from sanic.exceptions import ServerError
 from sanic.log import error_logger
@@ -15,13 +16,6 @@
 
 
 class WebSocketProtocol(HttpProtocol):
-
-    websocket: Optional[WebsocketImplProtocol]
-    websocket_timeout: float
-    websocket_max_size = Optional[int]
-    websocket_ping_interval = Optional[float]
-    websocket_ping_timeout = Optional[float]
-
     def __init__(
         self,
         *args,
@@ -35,7 +29,7 @@ def __init__(
         **kwargs,
     ):
         super().__init__(*args, **kwargs)
-        self.websocket = None
+        self.websocket: Optional[WebsocketImplProtocol] = None
         self.websocket_timeout = websocket_timeout
         self.websocket_max_size = websocket_max_size
         if websocket_max_queue is not None and websocket_max_queue > 0:
@@ -109,14 +103,22 @@ def close_if_idle(self):
             return super().close_if_idle()
 
     async def websocket_handshake(
-        self, request, subprotocols=Optional[Sequence[str]]
+        self, request, subprotocols: Optional[Sequence[str]] = None
     ):
         # let the websockets package do the handshake with the client
         try:
             if subprotocols is not None:
                 # subprotocols can be a set or frozenset,
                 # but ServerConnection needs a list
-                subprotocols = list(subprotocols)
+                subprotocols = cast(
+                    Optional[Sequence[Subprotocol]],
+                    list(
+                        [
+                            Subprotocol(subprotocol)
+                            for subprotocol in subprotocols
+                        ]
+                    ),
+                )
             ws_conn = ServerConnection(
                 max_size=self.websocket_max_size,
                 subprotocols=subprotocols,
@@ -131,21 +133,18 @@ async def websocket_handshake(
             )
             raise ServerError(msg, status_code=500)
         if 100 <= resp.status_code <= 299:
-            rbody = "".join(
-                [
-                    "HTTP/1.1 ",
-                    str(resp.status_code),
-                    " ",
-                    resp.reason_phrase,
-                    "\r\n",
-                ]
-            )
-            rbody += "".join(f"{k}: {v}\r\n" for k, v in resp.headers.items())
+            first_line = (
+                f"HTTP/1.1 {resp.status_code} {resp.reason_phrase}\r\n"
+            ).encode()
+            rbody = bytearray(first_line)
+            rbody += (
+                "".join(f"{k}: {v}\r\n" for k, v in resp.headers.items())
+            ).encode()
+            rbody += b"\r\n"
             if resp.body is not None:
-                rbody += f"\r\n{resp.body}\r\n\r\n"
-            else:
-                rbody += "\r\n"
-            await super().send(rbody.encode())
+                rbody += resp.body
+                rbody += b"\r\n\r\n"
+            await super().send(rbody)
         else:
             raise ServerError(resp.body, resp.status_code)
         self.websocket = WebsocketImplProtocol(