Cache area registry JSON serialize (#117847)

We already cache the entity and device registry, but since I never
used area until recently I did not have enough to notice that they
were not cached

homeassistant/components/config/area_registry.py

@@ -8,7 +8,7 @@ import voluptuous as vol
 
 from homeassistant.components import websocket_api
 from homeassistant.core import HomeAssistant, callback
-from homeassistant.helpers.area_registry import AreaEntry, async_get
+from homeassistant.helpers.area_registry import async_get
 
 
 @callback
@@ -32,7 +32,7 @@ def websocket_list_areas(
     registry = async_get(hass)
     connection.send_result(
         msg["id"],
-        [_entry_dict(entry) for entry in registry.async_list_areas()],
+        [entry.json_fragment for entry in registry.async_list_areas()],
     )
 
 
@@ -74,7 +74,7 @@ def websocket_create_area(
     except ValueError as err:
         connection.send_error(msg["id"], "invalid_info", str(err))
     else:
-        connection.send_result(msg["id"], _entry_dict(entry))
+        connection.send_result(msg["id"], entry.json_fragment)
 
 
 @websocket_api.websocket_command(
@@ -140,18 +140,4 @@ def websocket_update_area(
     except ValueError as err:
         connection.send_error(msg["id"], "invalid_info", str(err))
     else:
-        connection.send_result(msg["id"], _entry_dict(entry))
-
-
-@callback
-def _entry_dict(entry: AreaEntry) -> dict[str, Any]:
-    """Convert entry to API format."""
-    return {
-        "aliases": list(entry.aliases),
-        "area_id": entry.id,
-        "floor_id": entry.floor_id,
-        "icon": entry.icon,
-        "labels": list(entry.labels),
-        "name": entry.name,
-        "picture": entry.picture,
-    }
+        connection.send_result(msg["id"], entry.json_fragment)

homeassistant/helpers/area_registry.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 from collections.abc import Iterable
 import dataclasses
+from functools import cached_property
 from typing import Any, Literal, TypedDict
 
 from homeassistant.core import HomeAssistant, callback
@@ -12,6 +13,7 @@ from homeassistant.util.event_type import EventType
 from homeassistant.util.hass_dict import HassKey
 
 from . import device_registry as dr, entity_registry as er
+from .json import json_bytes, json_fragment
 from .normalized_name_base_registry import (
     NormalizedNameBaseRegistryEntry,
     NormalizedNameBaseRegistryItems,
@@ -56,7 +58,7 @@ class EventAreaRegistryUpdatedData(TypedDict):
     area_id: str
 
 
-@dataclasses.dataclass(frozen=True, kw_only=True, slots=True)
+@dataclasses.dataclass(frozen=True, kw_only=True)
 class AreaEntry(NormalizedNameBaseRegistryEntry):
     """Area Registry Entry."""
 
@@ -67,6 +69,23 @@ class AreaEntry(NormalizedNameBaseRegistryEntry):
     labels: set[str] = dataclasses.field(default_factory=set)
     picture: str | None
 
+    @cached_property
+    def json_fragment(self) -> json_fragment:
+        """Return a JSON representation of this AreaEntry."""
+        return json_fragment(
+            json_bytes(
+                {
+                    "aliases": list(self.aliases),
+                    "area_id": self.id,
+                    "floor_id": self.floor_id,
+                    "icon": self.icon,
+                    "labels": list(self.labels),
+                    "name": self.name,
+                    "picture": self.picture,
+                }
+            )
+        )
+
 
 class AreaRegistryStore(Store[AreasRegistryStoreData]):
     """Store area registry data."""