Provide asn_n_members=1 when opening dataset for Step to call `ge…

…t_crds_parameters` (#142)

CHANGES.rst

@@ -6,6 +6,8 @@
 - Remove bundled ``configobj`` package in favor of the ``configobj`` package
   bundled into ``astropy``. [#122]
 - Fix ``datetime.utcnow()`` DeprecationWarning [#134]
+- Provide ``asn_n_members=1`` when opening the ``Step`` dataset for
+  ``get_crds_parameters`` [#142]
 
 0.5.1 (2023-10-02)
 ==================

src/stpipe/step.py

@@ -840,12 +840,12 @@ def get_config_from_reference(cls, dataset, disable=None, crds_observatory=None)
             # If the dataset is not an operable instance of AbstractDataModel,
             # log as such and return an empty config object
             try:
-                model = cls._datamodels_open(dataset)
-                if isinstance(model, Sequence):
-                    # Pull out first model in ModelContainer
-                    model = model[0]
-                crds_parameters = model.get_crds_parameters()
-                crds_observatory = model.crds_observatory
+                with cls._datamodels_open(dataset, asn_n_members=1) as model:
+                    if isinstance(model, Sequence):
+                        # Pull out first model in ModelContainer
+                        model = model[0]
+                    crds_parameters = model.get_crds_parameters()
+                    crds_observatory = model.crds_observatory
             except (OSError, TypeError, ValueError):
                 logger.warning("Input dataset is not an instance of AbstractDataModel.")
                 disable = True