Fix async functions should not call open()

% [`ruff --select=ASYNC .`](https://beta.ruff.rs/docs/rules/open-sleep-or-subprocess-in-async-function)
2	ASYNC101	[ ] Async functions should not call `open`, `time.sleep`, or `subprocess` methods

examples/web_ws.py

@@ -8,6 +8,8 @@
 import os
 from typing import List, Union
 
+import aiofiles
+
 from aiohttp import web
 
 WS_FILE = os.path.join(os.path.dirname(__file__), "websocket.html")
@@ -18,8 +20,8 @@ async def wshandler(request: web.Request) -> Union[web.WebSocketResponse, web.Re
     resp = web.WebSocketResponse()
     available = resp.can_prepare(request)
     if not available:
-        with open(WS_FILE, "rb") as fp:
-            return web.Response(body=fp.read(), content_type="text/html")
+        async with aiofiles.open(WS_FILE, "rb") as fp:
+            return web.Response(body=await fp.read(), content_type="text/html")
 
     await resp.prepare(request)
 

requirements/lint.txt

@@ -4,4 +4,5 @@ mypy==0.982; implementation_name=="cpython"
 pre-commit==2.17.0
 pytest==6.2.5
 slotscheck==0.8.0
+types-aiofiles==23.1.0.4
 uvloop==0.17.0; platform_system!="Windows"

requirements/test.txt

@@ -1,4 +1,5 @@
 -r base.txt
+aiofiles
 Brotli==1.0.9
 coverage==6.4.2
 cryptography==36.0.1; platform_machine!="i686" # no 32-bit wheels; no python 3.9 wheels yet

tools/bench-asyncio-write.py

@@ -5,6 +5,8 @@
 import signal
 from typing import List, Tuple
 
+import aiofiles
+
 PORT = 8888
 
 server = os.fork()
@@ -123,9 +125,9 @@ async def bench(job_title, w, body, base=None):
         base = await bench(t, writes[0], c)
         for w in writes[1:]:
             await bench("", w, c, base)
-    with open("bench.md", "w") as f:
+    async with aiofiles.open("bench.md", "w") as f:
         for line in res:
-            f.write("| {} |\n".format(" | ".join(line)))
+            await f.write("| {} |\n".format(" | ".join(line)))
 
 
 loop = asyncio.get_event_loop()