Reject an unknown publish= value

esphome/core/entity_helpers.py

@@ -559,6 +559,8 @@ class SubEntities:
             raise ValueError(f"{entity_id}: apply= needs a parent")
         if publish is not None and (apply is None or self.apply_entity.publish is None):
             raise ValueError(f"{entity_id}: publish= needs apply= on a stateful domain")
+        if publish not in (None, "before", "after"):
+            raise ValueError(f'{entity_id}: publish= must be "before" or "after"')
 
         if apply is None:
             var = await self.new_entity(conf, *args, **kwargs)

tests/unit_tests/core/test_entity_helpers.py

@@ -1458,6 +1458,12 @@ async def test_sub_entities_apply_parent_id(
             {"publish": "before"},
             "publish= needs",
         ),
+        (
+            _SWITCH_APPLY,
+            _apply_conf("k_id"),
+            {"apply": "x()", "publish": "Before"},
+            "must be",
+        ),
     ],
 )
 async def test_sub_entities_apply_errors(