Generate HomeAssistantError message from English translations (#113305)

* Fetch exception message from translation cache

* Improve tests

* Return translation key without path, cleanup

* Fetch translations when string variant is requested

* Move import

* revert changes ConfigValidationError

* mypy

* Remove _str__ method instead

* Type _message for mqtt template exception classes

* Revert changes made to test_config.py

* Undo changes TemplateError

* Follow up comments and test coverage

tests/test_exceptions.py

@@ -2,12 +2,17 @@
 
 from __future__ import annotations
 
+from typing import Any
+from unittest.mock import patch
+
 import pytest
 
+from homeassistant.core import HomeAssistant
 from homeassistant.exceptions import (
     ConditionErrorContainer,
     ConditionErrorIndex,
     ConditionErrorMessage,
+    HomeAssistantError,
     TemplateError,
 )
 
@@ -62,3 +67,55 @@ def test_template_message(arg: str | Exception, expected: str) -> None:
     """Ensure we can create TemplateError."""
     template_error = TemplateError(arg)
     assert str(template_error) == expected
+
+
+@pytest.mark.parametrize(
+    ("exception_args", "exception_kwargs", "args_base_class", "message"),
+    [
+        ((), {}, (), ""),
+        (("bla",), {}, ("bla",), "bla"),
+        ((None,), {}, (None,), "None"),
+        ((type_error_bla := TypeError("bla"),), {}, (type_error_bla,), "bla"),
+        (
+            (),
+            {"translation_domain": "test", "translation_key": "test"},
+            ("test",),
+            "test",
+        ),
+        (
+            (),
+            {"translation_domain": "test", "translation_key": "bla"},
+            ("bla",),
+            "{bla} from cache",
+        ),
+        (
+            (),
+            {
+                "translation_domain": "test",
+                "translation_key": "bla",
+                "translation_placeholders": {"bla": "Bla"},
+            },
+            ("bla",),
+            "Bla from cache",
+        ),
+    ],
+)
+async def test_home_assistant_error(
+    hass: HomeAssistant,
+    exception_args: tuple[Any,],
+    exception_kwargs: dict[str, Any],
+    args_base_class: tuple[Any],
+    message: str,
+) -> None:
+    """Test edge cases with HomeAssistantError."""
+
+    with patch(
+        "homeassistant.helpers.translation.async_get_cached_translations",
+        return_value={"component.test.exceptions.bla.message": "{bla} from cache"},
+    ):
+        with pytest.raises(HomeAssistantError) as exc:
+            raise HomeAssistantError(*exception_args, **exception_kwargs)
+        assert exc.value.args == args_base_class
+        assert str(exc.value) == message
+        # Get string of exception again from the cache
+        assert str(exc.value) == message