GH-106684: raise ResourceWarning when asyncio.StreamWriter is not closed (#107650)

Lib/test/test_asyncio/test_streams.py

@@ -1074,6 +1074,29 @@ os.close(fd)
 
         self.assertEqual(messages, [])
 
+    def test_unclosed_resource_warnings(self):
+        async def inner(httpd):
+            rd, wr = await asyncio.open_connection(*httpd.address)
+
+            wr.write(b'GET / HTTP/1.0\r\n\r\n')
+            data = await rd.readline()
+            self.assertEqual(data, b'HTTP/1.0 200 OK\r\n')
+            data = await rd.read()
+            self.assertTrue(data.endswith(b'\r\n\r\nTest message'))
+            with self.assertWarns(ResourceWarning):
+                del wr
+                gc.collect()
+
+
+        messages = []
+        self.loop.set_exception_handler(lambda loop, ctx: messages.append(ctx))
+
+        with test_utils.run_test_server() as httpd:
+            self.loop.run_until_complete(inner(httpd))
+
+        self.assertEqual(messages, [])
+
+
 
 if __name__ == '__main__':
     unittest.main()