add vals property and setter to delegate_parameter

docs/changes/newsfragments/6796.improved

@@ -0,0 +1 @@
+Add vals property and @vals.setter to qcodes.parameters.delegate_parameter.DelegateParameter to propagate the Validator from source to DelegateParameter.

src/qcodes/parameters/delegate_parameter.py

@@ -8,6 +8,8 @@
     from collections.abc import Sequence
     from datetime import datetime
 
+    from qcodes.validators import Validator
+
     from .parameter_base import ParamDataType, ParamRawDataType
 
 
@@ -171,9 +173,11 @@ def __init__(
 
         initial_cache_value = kwargs.pop("initial_cache_value", None)
         self.source = source
+        self._vals_override: Validator | None = None
         super().__init__(name, *args, **kwargs)
         self.label = kwargs.get("label", None)
         self.unit = kwargs.get("unit", None)
+        self.vals = kwargs.get("vals", None)
 
         # Hack While we inherit the settable status from the parent parameter
         # we do allow param.set_to to temporary override _settable in a
@@ -223,6 +227,23 @@ def unit(self) -> str:
     def unit(self, unit: str | None) -> None:
         self._unit_override = unit
 
+    @property
+    def vals(self) -> Validator | None:
+        """
+        The validator of the parameter. Read from source if not explicitly overwritten.
+        Set to None to disable overwrite.
+        """
+        if self._vals_override is not None:
+            return self._vals_override
+        elif self.source is not None:
+            return self.source.vals
+        else:
+            return None
+
+    @vals.setter
+    def vals(self, vals: Validator | None) -> None:
+        self._vals_override = vals
+
     @property
     def label(self) -> str:
         """
@@ -314,3 +335,5 @@ def validate(self, value: ParamDataType) -> None:
         super().validate(value)
         if self.source is not None:
             self.source.validate(self._from_value_to_raw_value(value))
+            if self.vals is not None:
+                self.vals.validate(value)

tests/parameter/test_delegate_parameter.py

@@ -574,18 +574,23 @@ def test_value_validation() -> None:
     source_param = Parameter("source", set_cmd=None, get_cmd=None)
     delegate_param = DelegateParameter("delegate", source=source_param)
 
+    # Test case where source parameter validator is None and delegate parameter validator is
+    # specified.
     delegate_param.vals = vals.Numbers(-10, 10)
     source_param.vals = None
     delegate_param.validate(1)
     with pytest.raises(ValueError):
         delegate_param.validate(11)
 
+    # Test where delegate parameter validator is None and source parameter validator is
+    # specified.
     delegate_param.vals = None
     source_param.vals = vals.Numbers(-5, 5)
     delegate_param.validate(1)
     with pytest.raises(ValueError):
         delegate_param.validate(6)
 
+    # Test case where source parameter validator is more restricted than delegate parameter.
     delegate_param.vals = vals.Numbers(-10, 10)
     source_param.vals = vals.Numbers(-5, 5)
     delegate_param.validate(1)
@@ -594,6 +599,33 @@ def test_value_validation() -> None:
     with pytest.raises(ValueError):
         delegate_param.validate(11)
 
+    # Test case that the order of setting validator on source and delegate parameters does not matter.
+    source_param.vals = vals.Numbers(-5, 5)
+    delegate_param.vals = vals.Numbers(-10, 10)
+    delegate_param.validate(1)
+    with pytest.raises(ValueError):
+        delegate_param.validate(6)
+    with pytest.raises(ValueError):
+        delegate_param.validate(11)
+
+    # Test case where delegate parameter validator is more restricted than source parameter.
+    delegate_param.vals = vals.Numbers(-5, 5)
+    source_param.vals = vals.Numbers(-10, 10)
+    delegate_param.validate(1)
+    with pytest.raises(ValueError):
+        delegate_param.validate(6)
+    with pytest.raises(ValueError):
+        delegate_param.validate(11)
+
+    # Test case that the order of setting validator on source and delegate parameters does not matter.
+    source_param.vals = vals.Numbers(-10, 10)
+    delegate_param.vals = vals.Numbers(-5, 5)
+    delegate_param.validate(1)
+    with pytest.raises(ValueError):
+        delegate_param.validate(6)
+    with pytest.raises(ValueError):
+        delegate_param.validate(11)
+
 
 def test_value_validation_with_offset_and_scale() -> None:
     source_param = Parameter(