Fix TemplateError definition (#82570)

homeassistant/exceptions.py

@@ -25,9 +25,12 @@ class NoEntitySpecifiedError(HomeAssistantError):
 class TemplateError(HomeAssistantError):
     """Error during template rendering."""
 
-    def __init__(self, exception: Exception) -> None:
+    def __init__(self, exception: Exception | str) -> None:
         """Init the error."""
-        super().__init__(f"{exception.__class__.__name__}: {exception}")
+        if isinstance(exception, str):
+            super().__init__(exception)
+        else:
+            super().__init__(f"{exception.__class__.__name__}: {exception}")
 
 
 @attr.s

homeassistant/helpers/template.py

@@ -918,7 +918,7 @@ def _state_generator(
 def _get_state_if_valid(hass: HomeAssistant, entity_id: str) -> TemplateState | None:
     state = hass.states.get(entity_id)
     if state is None and not valid_entity_id(entity_id):
-        raise TemplateError(f"Invalid entity ID '{entity_id}'")  # type: ignore[arg-type]
+        raise TemplateError(f"Invalid entity ID '{entity_id}'")
     return _get_template_state_from_state(hass, entity_id, state)
 
 

tests/components/mqtt/test_trigger.py

@@ -194,7 +194,7 @@ async def test_non_allowed_templates(hass, calls, caplog):
     )
 
     assert (
-        "Got error 'TemplateError: str: Use of 'states' is not supported in limited templates' when setting up triggers"
+        "Got error 'TemplateError: Use of 'states' is not supported in limited templates' when setting up triggers"
         in caplog.text
     )
 

tests/test_exceptions.py

@@ -1,12 +1,17 @@
 """Test to verify that Home Assistant exceptions work."""
+from __future__ import annotations
+
+import pytest
+
 from homeassistant.exceptions import (
     ConditionErrorContainer,
     ConditionErrorIndex,
     ConditionErrorMessage,
+    TemplateError,
 )
 
 
-def test_conditionerror_format():
+def test_conditionerror_format() -> None:
     """Test ConditionError stringifiers."""
     error1 = ConditionErrorMessage("test", "A test error")
     assert str(error1) == "In 'test' condition: A test error"
@@ -43,3 +48,16 @@ In 'box' (item 2 of 2):
         == """In 'box':
   In 'test' condition: A test error"""
     )
+
+
+@pytest.mark.parametrize(
+    "arg, expected",
+    [
+        ("message", "message"),
+        (Exception("message"), "Exception: message"),
+    ],
+)
+def test_template_message(arg: str | Exception, expected: str) -> None:
+    """Ensure we can create TemplateError."""
+    template_error = TemplateError(arg)
+    assert str(template_error) == expected