Refactor entity registry JSON cache (home-assistant#85085)

* Refactor entity registry JSON cache

* Fix generator

* Tweak

* Improve string building

* Improve test coverage

* Override EntityRegistryItems.values to avoid __iter__ overhead

homeassistant/components/config/entity_registry.py

@@ -9,12 +9,7 @@
 from homeassistant.components import websocket_api
 from homeassistant.components.websocket_api import ERR_NOT_FOUND
 from homeassistant.components.websocket_api.decorators import require_admin
-from homeassistant.components.websocket_api.messages import (
-    IDEN_JSON_TEMPLATE,
-    IDEN_TEMPLATE,
-    message_to_json,
-)
-from homeassistant.core import Event, HomeAssistant, callback
+from homeassistant.core import HomeAssistant, callback
 from homeassistant.helpers import (
     config_validation as cv,
     device_registry as dr,
@@ -25,41 +20,6 @@
 async def async_setup(hass: HomeAssistant) -> bool:
     """Enable the Entity Registry views."""
 
-    cached_list_entities: str | None = None
-
-    @callback
-    def _async_clear_list_entities_cache(event: Event) -> None:
-        nonlocal cached_list_entities
-        cached_list_entities = None
-
-    @websocket_api.websocket_command(
-        {vol.Required("type"): "config/entity_registry/list"}
-    )
-    @callback
-    def websocket_list_entities(
-        hass: HomeAssistant,
-        connection: websocket_api.ActiveConnection,
-        msg: dict[str, Any],
-    ) -> None:
-        """Handle list registry entries command."""
-        nonlocal cached_list_entities
-        if not cached_list_entities:
-            registry = er.async_get(hass)
-            cached_list_entities = message_to_json(
-                websocket_api.result_message(
-                    IDEN_TEMPLATE,  # type: ignore[arg-type]
-                    [_entry_dict(entry) for entry in registry.entities.values()],
-                )
-            )
-        connection.send_message(
-            cached_list_entities.replace(IDEN_JSON_TEMPLATE, str(msg["id"]), 1)
-        )
-
-    hass.bus.async_listen(
-        er.EVENT_ENTITY_REGISTRY_UPDATED,
-        _async_clear_list_entities_cache,
-        run_immediately=True,
-    )
     websocket_api.async_register_command(hass, websocket_list_entities)
     websocket_api.async_register_command(hass, websocket_get_entity)
     websocket_api.async_register_command(hass, websocket_get_entities)
@@ -68,6 +28,33 @@ def websocket_list_entities(
     return True
 
 
+@websocket_api.websocket_command({vol.Required("type"): "config/entity_registry/list"})
+@callback
+def websocket_list_entities(
+    hass: HomeAssistant,
+    connection: websocket_api.ActiveConnection,
+    msg: dict[str, Any],
+) -> None:
+    """Handle list registry entries command."""
+    registry = er.async_get(hass)
+    # Build start of response message
+    msg_json_prefix = (
+        f'{{"id":{msg["id"]},"type": "{websocket_api.const.TYPE_RESULT}",'
+        f'"success":true,"result": ['
+    )
+    # Concatenate cached entity registry item JSON serializations
+    msg_json = (
+        msg_json_prefix
+        + ",".join(
+            entry.json_repr
+            for entry in registry.entities.values()
+            if entry.json_repr is not None
+        )
+        + "]}"
+    )
+    connection.send_message(msg_json)
+
+
 @websocket_api.websocket_command(
     {
         vol.Required("type"): "config/entity_registry/get",

homeassistant/helpers/entity_registry.py

@@ -10,7 +10,7 @@
 from __future__ import annotations
 
 from collections import UserDict
-from collections.abc import Callable, Iterable, Mapping
+from collections.abc import Callable, Iterable, Mapping, ValuesView
 import logging
 from typing import TYPE_CHECKING, Any, TypeVar, cast
 
@@ -42,10 +42,15 @@
 from homeassistant.exceptions import MaxLengthExceeded
 from homeassistant.loader import bind_hass
 from homeassistant.util import slugify, uuid as uuid_util
+from homeassistant.util.json import (
+    find_paths_unserializable_data,
+    format_unserializable_data,
+)
 
 from . import device_registry as dr, storage
 from .device_registry import EVENT_DEVICE_REGISTRY_UPDATED
 from .frame import report
+from .json import JSON_DUMP
 from .typing import UNDEFINED, UndefinedType
 
 if TYPE_CHECKING:
@@ -130,6 +135,8 @@ class RegistryEntry:
     translation_key: str | None = attr.ib(default=None)
     unit_of_measurement: str | None = attr.ib(default=None)
 
+    _json_repr: str | None = attr.ib(cmp=False, default=None, init=False, repr=False)
+
     @domain.default
     def _domain_default(self) -> str:
         """Compute domain value."""
@@ -145,6 +152,41 @@ def hidden(self) -> bool:
         """Return if entry is hidden."""
         return self.hidden_by is not None
 
+    @property
+    def json_repr(self) -> str | None:
+        """Return a cached JSON representation of the entry."""
+        if self._json_repr is not None:
+            return self._json_repr
+
+        try:
+            dict_repr = {
+                "area_id": self.area_id,
+                "config_entry_id": self.config_entry_id,
+                "device_id": self.device_id,
+                "disabled_by": self.disabled_by,
+                "entity_category": self.entity_category,
+                "entity_id": self.entity_id,
+                "has_entity_name": self.has_entity_name,
+                "hidden_by": self.hidden_by,
+                "icon": self.icon,
+                "id": self.id,
+                "name": self.name,
+                "original_name": self.original_name,
+                "platform": self.platform,
+                "translation_key": self.translation_key,
+                "unique_id": self.unique_id,
+            }
+            object.__setattr__(self, "_json_repr", JSON_DUMP(dict_repr))
+        except (ValueError, TypeError):
+            _LOGGER.error(
+                "Unable to serialize entry %s to JSON. Bad data found at %s",
+                self.entity_id,
+                format_unserializable_data(
+                    find_paths_unserializable_data(dict_repr, dump=JSON_DUMP)
+                ),
+            )
+        return self._json_repr
+
     @callback
     def write_unavailable_state(self, hass: HomeAssistant) -> None:
         """Write the unavailable state to the state machine."""
@@ -268,6 +310,10 @@ def __init__(self) -> None:
         self._entry_ids: dict[str, RegistryEntry] = {}
         self._index: dict[tuple[str, str, str], str] = {}
 
+    def values(self) -> ValuesView[RegistryEntry]:
+        """Return the underlying values to avoid __iter__ overhead."""
+        return self.data.values()
+
     def __setitem__(self, key: str, entry: RegistryEntry) -> None:
         """Add an item."""
         if key in self:

tests/components/config/test_entity_registry.py

@@ -6,7 +6,6 @@
 from homeassistant.const import ATTR_ICON
 from homeassistant.helpers.device_registry import DeviceEntryDisabler
 from homeassistant.helpers.entity_registry import (
-    EVENT_ENTITY_REGISTRY_UPDATED,
     RegistryEntry,
     RegistryEntryDisabler,
     RegistryEntryHider,
@@ -95,6 +94,9 @@ async def test_list_entities(hass, client):
         },
     ]
 
+    class Unserializable:
+        """Good luck serializing me."""
+
     mock_registry(
         hass,
         {
@@ -104,13 +106,15 @@ async def test_list_entities(hass, client):
                 platform="test_platform",
                 name="Hello World",
             ),
+            "test_domain.name_2": RegistryEntry(
+                entity_id="test_domain.name_2",
+                unique_id="6789",
+                platform="test_platform",
+                name=Unserializable(),
+            ),
         },
     )
 
-    hass.bus.async_fire(
-        EVENT_ENTITY_REGISTRY_UPDATED,
-        {"action": "create", "entity_id": "test_domain.no_name"},
-    )
     await client.send_json({"id": 6, "type": "config/entity_registry/list"})
     msg = await client.receive_json()