Serialize websocket event message once (#40453)

Since most of the json serialize work for the websocket was done
multiple times for the same message, we can avoid the overhead
of serializing the same message many times (once per websocket
client) with a cache.

homeassistant/components/websocket_api/http.py

@@ -11,17 +11,11 @@ from homeassistant.components.http import HomeAssistantView
 from homeassistant.const import EVENT_HOMEASSISTANT_STOP
 from homeassistant.core import callback
 from homeassistant.helpers.event import async_call_later
-from homeassistant.util.json import (
-    find_paths_unserializable_data,
-    format_unserializable_data,
-)
 
 from .auth import AuthPhase, auth_required_message
 from .const import (
     CANCELLATION_ERRORS,
     DATA_CONNECTIONS,
-    ERR_UNKNOWN_ERROR,
-    JSON_DUMP,
     MAX_PENDING_MSG,
     PENDING_MSG_PEAK,
     PENDING_MSG_PEAK_TIME,
@@ -30,7 +24,7 @@ from .const import (
     URL,
 )
 from .error import Disconnect
-from .messages import error_message
+from .messages import message_to_json
 
 # mypy: allow-untyped-calls, allow-untyped-defs, no-check-untyped-defs
 
@@ -72,27 +66,10 @@ class WebSocketHandler:
 
                 self._logger.debug("Sending %s", message)
 
-                if isinstance(message, str):
-                    await self.wsock.send_str(message)
-                    continue
+                if not isinstance(message, str):
+                    message = message_to_json(message)
 
-                try:
-                    dumped = JSON_DUMP(message)
-                except (ValueError, TypeError):
-                    await self.wsock.send_json(
-                        error_message(
-                            message["id"], ERR_UNKNOWN_ERROR, "Invalid JSON in response"
-                        )
-                    )
-                    self._logger.error(
-                        "Unable to serialize to JSON. Bad data found at %s",
-                        format_unserializable_data(
-                            find_paths_unserializable_data(message, dump=JSON_DUMP)
-                        ),
-                    )
-                    continue
-
-                await self.wsock.send_str(dumped)
+                await self.wsock.send_str(message)
 
         # Clean up the peaker checker when we shut down the writer
         if self._peak_checker_unsub: