Fix scene integration doing blocking I/O in the event loop to import platforms (#113391)

homeassistant/components/homeassistant/__init__.py

@@ -35,6 +35,11 @@ from homeassistant.helpers.service import (
 from homeassistant.helpers.template import async_load_custom_templates
 from homeassistant.helpers.typing import ConfigType
 
+# The scene integration will do a late import of scene
+# so we want to make sure its loaded with the component
+# so its already in memory when its imported so the import
+# does not do blocking I/O in the event loop.
+from . import scene as scene_pre_import  # noqa: F401
 from .const import (
     DATA_EXPOSED_ENTITIES,
     DATA_STOP_HANDLER,

homeassistant/components/scene/__init__.py

@@ -32,15 +32,13 @@ def _hass_domain_validator(config: dict[str, Any]) -> dict[str, Any]:
 
 def _platform_validator(config: dict[str, Any]) -> dict[str, Any]:
     """Validate it is a valid  platform."""
+    platform_name = config[CONF_PLATFORM]
     try:
-        platform = importlib.import_module(f".{config[CONF_PLATFORM]}", __name__)
+        platform = importlib.import_module(
+            f"homeassistant.components.{platform_name}.scene"
+        )
     except ImportError:
-        try:
-            platform = importlib.import_module(
-                f"homeassistant.components.{config[CONF_PLATFORM]}.scene"
-            )
-        except ImportError:
-            raise vol.Invalid("Invalid platform specified") from None
+        raise vol.Invalid("Invalid platform specified") from None
 
     if not hasattr(platform, "PLATFORM_SCHEMA"):
         return config

tests/components/scene/test_init.py

@@ -262,3 +262,15 @@ async def turn_off_lights(hass, entity_ids):
         blocking=True,
     )
     await hass.async_block_till_done()
+
+
+async def test_invalid_platform(
+    hass: HomeAssistant, caplog: pytest.LogCaptureFixture
+) -> None:
+    """Test invalid platform."""
+    await async_setup_component(
+        hass, scene.DOMAIN, {scene.DOMAIN: {"platform": "does_not_exist"}}
+    )
+    await hass.async_block_till_done()
+    assert "Invalid platform specified" in caplog.text
+    assert "does_not_exist" in caplog.text