Avoid rechecking for missing platforms in the loader (#111204)

homeassistant/loader.py

@@ -53,6 +53,7 @@ _LOGGER = logging.getLogger(__name__)
 
 DATA_COMPONENTS = "components"
 DATA_INTEGRATIONS = "integrations"
+DATA_MISSING_PLATFORMS = "missing_platforms"
 DATA_CUSTOM_COMPONENTS = "custom_components"
 PACKAGE_CUSTOM_COMPONENTS = "custom_components"
 PACKAGE_BUILTIN = "homeassistant.components"
@@ -185,6 +186,7 @@ def async_setup(hass: HomeAssistant) -> None:
     _async_mount_config_dir(hass)
     hass.data[DATA_COMPONENTS] = {}
     hass.data[DATA_INTEGRATIONS] = {}
+    hass.data[DATA_MISSING_PLATFORMS] = {}
 
 
 def manifest_from_legacy_module(domain: str, module: ModuleType) -> Manifest:
@@ -842,9 +844,19 @@ class Integration:
         if full_name in cache:
             return cache[full_name]
 
+        missing_platforms_cache: dict[str, ImportError] = self.hass.data[
+            DATA_MISSING_PLATFORMS
+        ]
+        if full_name in missing_platforms_cache:
+            raise missing_platforms_cache[full_name]
+
         try:
             cache[full_name] = self._import_platform(platform_name)
-        except ImportError:
+        except ImportError as ex:
+            if self.domain in cache:
+                # If the domain is loaded, cache that the platform
+                # does not exist so we do not try to load it again
+                missing_platforms_cache[full_name] = ex
             raise
         except Exception as err:
             _LOGGER.exception(
@@ -1022,10 +1034,10 @@ def _load_file(
     Only returns it if also found to be valid.
     Async friendly.
     """
-    with suppress(KeyError):
-        return hass.data[DATA_COMPONENTS][comp_or_platform]  # type: ignore[no-any-return]
-
-    cache = hass.data[DATA_COMPONENTS]
+    cache: dict[str, ComponentProtocol] = hass.data[DATA_COMPONENTS]
+    module: ComponentProtocol | None
+    if module := cache.get(comp_or_platform):
+        return module
 
     for path in (f"{base}.{comp_or_platform}" for base in base_paths):
         try:

tests/test_loader.py

@@ -188,6 +188,41 @@ async def test_get_integration_exceptions(hass: HomeAssistant) -> None:
         assert hue_light == integration.get_platform("light")
 
 
+async def test_get_platform_caches_failures_when_component_loaded(
+    hass: HomeAssistant,
+) -> None:
+    """Test get_platform cache failures only when the component is loaded."""
+    integration = await loader.async_get_integration(hass, "hue")
+
+    with pytest.raises(ImportError), patch(
+        "homeassistant.loader.importlib.import_module", side_effect=ImportError("Boom")
+    ):
+        assert integration.get_component() == hue
+
+    with pytest.raises(ImportError), patch(
+        "homeassistant.loader.importlib.import_module", side_effect=ImportError("Boom")
+    ):
+        assert integration.get_platform("light") == hue_light
+
+    # Hue is not loaded so we should still hit the import_module path
+    with pytest.raises(ImportError), patch(
+        "homeassistant.loader.importlib.import_module", side_effect=ImportError("Boom")
+    ):
+        assert integration.get_platform("light") == hue_light
+
+    assert integration.get_component() == hue
+
+    # Hue is loaded so we should cache the import_module failure now
+    with pytest.raises(ImportError), patch(
+        "homeassistant.loader.importlib.import_module", side_effect=ImportError("Boom")
+    ):
+        assert integration.get_platform("light") == hue_light
+
+    # Hue is loaded and the last call should have cached the import_module failure
+    with pytest.raises(ImportError):
+        assert integration.get_platform("light") == hue_light
+
+
 async def test_get_integration_legacy(
     hass: HomeAssistant, enable_custom_integrations: None
 ) -> None: