Merge pull request #4655 from MichaelGoulding/param_metadata_snaphot

InstrumentBase and ParameterBase now call snapshot() on _meta_attrs attributes that inherit from Metadatable.

docs/changes/newsfragments/4655.improved

@@ -0,0 +1 @@
+InstrumentBase and ParameterBase now call snapshot() on _meta_attrs attributes that inherit from Metadatable.

qcodes/instrument/instrument_base.py

@@ -293,8 +293,13 @@ def snapshot_base(
                 snap["parameters"][name] = param.snapshot(update=False)
 
         for attr in set(self._meta_attrs):
-            if hasattr(self, attr):
-                snap[attr] = getattr(self, attr)
+            val = getattr(self, attr, None)
+            if val is not None:
+                if isinstance(val, Metadatable):
+                    snap[attr] = val.snapshot(update=update)
+                else:
+                    snap[attr] = val
+
         return snap
 
     def print_readable_snapshot(

qcodes/parameters/parameter_base.py

@@ -451,6 +451,8 @@ def snapshot_base(
                     attr_strip = attr.lstrip("_")  # strip leading underscores
                     if isinstance(val, Validator):
                         state[attr_strip] = repr(val)
+                    elif isinstance(val, Metadatable):
+                        state[attr_strip] = val.snapshot(update=update)
                     else:
                         state[attr_strip] = val
 

qcodes/tests/test_instrument.py

@@ -10,6 +10,7 @@
 
 from qcodes.instrument import Instrument, InstrumentBase, find_or_create_instrument
 from qcodes.parameters import Function, Parameter
+from qcodes.utils.metadata import Metadatable
 
 from .instrument_mocks import (
     DummyChannelInstrument,
@@ -424,3 +425,47 @@ def test_snapshot_and_meta_attrs():
 
     assert '__class__' in snapshot
     assert 'InstrumentBase' in snapshot['__class__']
+
+
+class TestSnapshotType(Metadatable):
+    def __init__(self, sample_value: int) -> None:
+        super().__init__()
+        self.sample_value = sample_value
+
+    def snapshot_base(self, update=True, params_to_skip_update=None):
+        return {"sample_key": self.sample_value}
+
+
+class TestInstrument(InstrumentBase):
+    def __init__(self, name, label) -> None:
+        super().__init__(name, label=label)
+        self._meta_attrs.extend(["test_attribute"])
+        self._test_attribute = TestSnapshotType(12)
+
+    @property
+    def test_attribute(self) -> TestSnapshotType:
+        return self._test_attribute
+
+
+def test_snapshot_and_meta_attrs2():
+    """Test snapshot of child of InstrumentBase which contains _meta_attrs attribute that is itself Metadatable"""
+    instr = TestInstrument("instr", label="Label")
+
+    assert instr.name == "instr"
+
+    assert hasattr(instr, "_meta_attrs")
+    assert instr._meta_attrs == ["name", "label", "test_attribute"]
+
+    snapshot = instr.snapshot()
+
+    assert "name" in snapshot
+    assert "instr" == snapshot["name"]
+
+    assert "label" in snapshot
+    assert "Label" == snapshot["label"]
+
+    assert "__class__" in snapshot
+    assert "TestInstrument" in snapshot["__class__"]
+
+    assert "test_attribute" in snapshot
+    assert {"sample_key": 12} == snapshot["test_attribute"]