[core] Let cv.rename_key pass non-dict input through (#20331)

esphome/config_validation.py

@@ -2872,9 +2872,14 @@ def rename_key(
     When ``removed_in`` is set, a deprecation warning is logged if the old key is
     present. Pass ``component`` (the platform/component name) alongside
     ``removed_in`` so the warning identifies where it originates.
+
+    Input that is not a dictionary is returned unchanged, so the schema that
+    follows reports it as a normal configuration error.
     """
 
     def validator(config: dict) -> dict:
+        if not isinstance(config, dict):
+            return config
         config = config.copy()
         if old_key in config:
             has_at_most_one_key(old_key, new_key)(config)

tests/unit_tests/test_config_validation.py

@@ -3120,6 +3120,11 @@ def test_rename_key_absent() -> None:
     assert cv.rename_key("old", "new")({"other": 5}) == {"other": 5}
 
 
+@pytest.mark.parametrize("value", ["an_id", 1, None, ["old"]])
+def test_rename_key_non_dict_passes_through(value: object) -> None:
+    assert cv.rename_key("old", "new")(value) == value
+
+
 def test_rename_key_no_removed_in_is_silent(
     caplog: pytest.LogCaptureFixture,
 ) -> None: