Add multi select support to config validation and to custom serializer

homeassistant/helpers/config_validation.py

@@ -588,6 +588,23 @@ def ensure_list_csv(value: Any) -> List:
     return ensure_list(value)
 
 
+def multi_select(options: dict) -> Callable[[List], List]:
+    """Multi select validator returning list of selected values."""
+
+    def validator(selected: List) -> list:
+        """Return list of selected values."""
+        if not isinstance(selected, list):
+            raise vol.Invalid("Not a list")
+
+        for value in selected:
+            if value not in options:
+                raise vol.Invalid(f"{value} is not a valid option")
+
+        return selected
+
+    return validator
+
+
 def deprecated(
     key: str,
     replacement_key: Optional[str] = None,
@@ -713,6 +730,9 @@ 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"}
+
     return voluptuous_serialize.UNSUPPORTED
 
 

tests/helpers/test_config_validation.py

@@ -472,6 +472,22 @@ def test_datetime():
     schema("2016-11-23T18:59:08")
 
 
+def test_multi_select():
+    """Test multi select validation.
+
+    Expected behavior:
+        - Will not accept any input but a list
+        - Will not accept selections outside of configured scope
+    """
+    schema = vol.Schema(cv.multi_select({"paulus": "Paulus", "robban": "Robban"}))
+
+    with pytest.raises(vol.Invalid):
+        schema("robban")
+        schema(["paulus", "martinhj"])
+
+    schema(["robban", "paulus"])
+
+
 @pytest.fixture
 def schema():
     """Create a schema used for testing deprecation."""