Adjust importlib helper to avoid leaking memory on re-raise (#115377)

homeassistant/helpers/importlib.py

@@ -30,11 +30,9 @@ async def async_import_module(hass: HomeAssistant, name: str) -> ModuleType:
     if module := cache.get(name):
         return module
 
-    failure_cache: dict[str, BaseException] = hass.data.setdefault(
-        DATA_IMPORT_FAILURES, {}
-    )
-    if exception := failure_cache.get(name):
-        raise exception
+    failure_cache: dict[str, bool] = hass.data.setdefault(DATA_IMPORT_FAILURES, {})
+    if name in failure_cache:
+        raise ModuleNotFoundError(f"{name} not found", name=name)
 
     import_futures: dict[str, asyncio.Future[ModuleType]]
     import_futures = hass.data.setdefault(DATA_IMPORT_FUTURES, {})
@@ -51,7 +49,8 @@ async def async_import_module(hass: HomeAssistant, name: str) -> ModuleType:
         module = await hass.async_add_import_executor_job(_get_module, cache, name)
         import_future.set_result(module)
     except BaseException as ex:
-        failure_cache[name] = ex
+        if isinstance(ex, ModuleNotFoundError):
+            failure_cache[name] = True
         import_future.set_exception(ex)
         with suppress(BaseException):
             # Set the exception retrieved flag on the future since

tests/helpers/test_importlib.py

@@ -41,16 +41,40 @@ async def test_async_import_module_failures(hass: HomeAssistant) -> None:
     with (
         patch(
             "homeassistant.helpers.importlib.importlib.import_module",
-            side_effect=ImportError,
+            side_effect=ValueError,
         ),
-        pytest.raises(ImportError),
+        pytest.raises(ValueError),
+    ):
+        await importlib.async_import_module(hass, "test.module")
+
+    mock_module = MockModule()
+    # The failure should be not be cached
+    with (
+        patch(
+            "homeassistant.helpers.importlib.importlib.import_module",
+            return_value=mock_module,
+        ),
+    ):
+        assert await importlib.async_import_module(hass, "test.module") is mock_module
+
+
+async def test_async_import_module_failure_caches_module_not_found(
+    hass: HomeAssistant,
+) -> None:
+    """Test importing a module caches ModuleNotFound."""
+    with (
+        patch(
+            "homeassistant.helpers.importlib.importlib.import_module",
+            side_effect=ModuleNotFoundError,
+        ),
+        pytest.raises(ModuleNotFoundError),
     ):
         await importlib.async_import_module(hass, "test.module")
 
     mock_module = MockModule()
     # The failure should be cached
     with (
-        pytest.raises(ImportError),
+        pytest.raises(ModuleNotFoundError),
         patch(
             "homeassistant.helpers.importlib.importlib.import_module",
             return_value=mock_module,