Change multi_select config validator to class (#31828)

* Move multi_select to class

* Fix serializer and add test

* Serializer should also return options

homeassistant/helpers/config_validation.py

@@ -588,22 +588,24 @@ def ensure_list_csv(value: Any) -> List:
     return ensure_list(value)
 
 
-def multi_select(options: dict) -> Callable[[List], List]:
+class multi_select:
     """Multi select validator returning list of selected values."""
 
-    def validator(selected: List) -> list:
-        """Return list of selected values."""
+    def __init__(self, options: dict) -> None:
+        """Initialize multi select."""
+        self.options = options
+
+    def __call__(self, selected: list) -> list:
+        """Validate input."""
         if not isinstance(selected, list):
             raise vol.Invalid("Not a list")
 
         for value in selected:
-            if value not in options:
+            if value not in self.options:
                 raise vol.Invalid(f"{value} is not a valid option")
 
         return selected
 
-    return validator
-
 
 def deprecated(
     key: str,
@@ -730,8 +732,8 @@ def custom_serializer(schema: Any) -> Any:
     if schema is positive_time_period_dict:
         return {"type": "positive_time_period_dict"}
 
-    if schema is multi_select:
-        return {"type": "multi_select"}
+    if isinstance(schema, multi_select):
+        return {"type": "multi_select", "options": schema.options}
 
     return voluptuous_serialize.UNSUPPORTED
 

tests/helpers/test_config_validation.py

@@ -488,6 +488,14 @@ def test_multi_select():
     schema(["robban", "paulus"])
 
 
+def test_multi_select_in_serializer():
+    """Test multi_select with custom_serializer."""
+    assert cv.custom_serializer(cv.multi_select({"paulus": "Paulus"})) == {
+        "type": "multi_select",
+        "options": {"paulus": "Paulus"},
+    }
+
+
 @pytest.fixture
 def schema():
     """Create a schema used for testing deprecation."""