Improve InstrumentRef parameter

Support looking up any Instrument as long as the name is known, not just the same as the bound instrument

Author: jenshnielsen

src/qcodes/parameters/specialized_parameters.py

@@ -8,8 +8,9 @@
 
 import warnings
 from time import perf_counter
-from typing import TYPE_CHECKING, Any, ClassVar, Literal
+from typing import TYPE_CHECKING, Any, ClassVar, Generic, Literal
 
+from qcodes.parameters.parameter_base import InstrumentTypeVar_co
 from qcodes.utils import QCoDeSDeprecationWarning
 from qcodes.validators import Strings, Validator
 
@@ -18,7 +19,7 @@
 if TYPE_CHECKING:
     from collections.abc import Callable
 
-    from qcodes.instrument import InstrumentBase
+    from qcodes.instrument import Instrument
 
 
 class ElapsedTimeParameter(Parameter):
@@ -96,7 +97,9 @@ def t0(self) -> float:
         return self._t0
 
 
-class InstrumentRefParameter(Parameter):
+class InstrumentRefParameter(
+    Parameter[str, InstrumentTypeVar_co], Generic[InstrumentTypeVar_co]
+):
     """
     An instrument reference parameter.
 
@@ -134,12 +137,12 @@ def __init__(
         self,
         name: str,
         *args: Any,
-        instrument: InstrumentBase | None = None,
+        instrument: InstrumentTypeVar_co = None,
         label: str | None = None,
         unit: str | None = None,
         get_cmd: str | Callable[..., Any] | Literal[False] | None = None,
         set_cmd: str | Callable[..., Any] | Literal[False] | None = None,
-        initial_value: float | str | None = None,
+        initial_value: str | None = None,
         max_val_age: float | None = None,
         vals: Validator[Any] | None = None,
         docstring: str | None = None,
@@ -229,16 +232,15 @@ def __init__(
             **kwargs,
         )
 
-    # TODO(nulinspiratie) check class works now it's subclassed from Parameter
-    def get_instr(self) -> InstrumentBase:
+    def get_instr(self) -> Instrument | None:
         """
         Returns the instance of the instrument with the name equal to the
         value of this parameter.
         """
+        # lazy import to avoid circular import
+        # since Instrument module depends on parameer module
+        from qcodes.instrument import Instrument  # noqa: PLC0415
+
         ref_instrument_name = self.get()
-        # note that _instrument refers to the instrument this parameter belongs
-        # to, while the ref_instrument_name is the instrument that is the value
-        # of this parameter.
-        if self._instrument is None:
-            raise RuntimeError("InstrumentRefParameter is not bound to an instrument.")
-        return self._instrument.find_instrument(ref_instrument_name)
+
+        return Instrument.find_instrument(ref_instrument_name)

tests/parameter/test_instrument_ref_parameter.py

@@ -9,28 +9,32 @@
     from collections.abc import Generator
 
 
+class DummyHolder(DummyInstrument):
+    def __init__(self, name: str) -> None:
+        super().__init__(name)
+        self.test = self.add_parameter(
+            "test",
+            parameter_class=InstrumentRefParameter,
+            initial_value=None,
+        )
+
+
 @pytest.fixture(name="instrument_a")
-def _make_instrument_a() -> "Generator[DummyInstrument, None, None]":
-    a = DummyInstrument("dummy_holder")
-    try:
-        yield a
-    finally:
-        a.close()
+def _make_instrument_a() -> "Generator[DummyHolder, None, None]":
+
+    a = DummyHolder("dummy_holder")
+    yield a
+    a.close()
 
 
 @pytest.fixture(name="instrument_d")
 def _make_instrument_d() -> "Generator[DummyInstrument, None, None]":
     d = DummyInstrument("dummy")
-    try:
-        yield d
-    finally:
-        d.close()
+    yield d
+    d.close()
 
 
-def test_get_instr(
-    instrument_a: DummyInstrument, instrument_d: DummyInstrument
-) -> None:
-    instrument_a.add_parameter("test", parameter_class=InstrumentRefParameter)
+def test_get_instr(instrument_a: DummyHolder, instrument_d: DummyInstrument) -> None:
 
     instrument_a.test.set(instrument_d.name)