Add source validators to delegate parameter validator

This will ensure that when the validator is used to find the datatype of a parameter it can be detected correctly

src/qcodes/parameters/delegate_parameter.py

@@ -8,6 +8,8 @@
     from collections.abc import Sequence
     from datetime import datetime
 
+    from qcodes.validators.validators import Validator
+
     from .parameter_base import ParamDataType, ParamRawDataType
 
 
@@ -314,3 +316,18 @@ 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))
+
+    @property
+    def validators(self) -> tuple[Validator, ...]:
+        """
+        Tuple of all validators associated with the parameter. Note that this
+        includes validators of the source parameter if source parameter is set
+        and has any validators.
+
+        :getter: All validators associated with the parameter.
+        """
+        source_validators: tuple[Validator, ...] = (
+            self.source.validators if self.source is not None else ()
+        )
+
+        return source_validators + tuple(self._vals)

src/qcodes/parameters/parameter_base.py

@@ -382,9 +382,10 @@ def vals(self) -> Validator | None:
             RuntimeError: If removing the first validator when more than one validator is set.
 
         """
+        validators = self.validators
 
-        if len(self._vals):
-            return self._vals[0]
+        if len(validators):
+            return validators[0]
         else:
             return None
 

tests/parameter/test_delegate_parameter.py

@@ -627,6 +627,19 @@ def test_value_validation() -> None:
         delegate_param.validate(11)
 
 
+def test_validator_delegates_as_expected() -> None:
+    source_param = Parameter("source", set_cmd=None, get_cmd=None)
+    delegate_param = DelegateParameter("delegate", source=source_param)
+    some_validator = vals.Numbers(-10, 10)
+    source_param.vals = some_validator
+    delegate_param.vals = None
+    delegate_param.validate(1)
+    with pytest.raises(ValueError):
+        delegate_param.validate(11)
+    assert delegate_param.validators == (some_validator,)
+    assert delegate_param.vals == some_validator
+
+
 def test_value_validation_with_offset_and_scale() -> None:
     source_param = Parameter(
         "source", set_cmd=None, get_cmd=None, vals=vals.Numbers(-5, 5)