Add some support for opening SSC models (#448)

changes/448.feature.rst

@@ -0,0 +1 @@
+Add support for opening SSC models using ``rdm_open``.

src/roman_datamodels/datamodels/_utils.py

@@ -108,5 +108,16 @@ def rdm_open(init, memmap=False, **kwargs):
         if (model_type := type(asdf_file.tree["roman"])) in MODEL_REGISTRY:
             return MODEL_REGISTRY[model_type](asdf_file, **kwargs)
 
+        # Check if the datamodel is a GDPS datamodel
+        try:
+            import roman_gdps  # noqa: F401
+        except ImportError as err:
+            asdf_file.close()
+            raise ImportError("Please install roman-gdps to allow opening GDPS datamodels") from err
+
+        # We assume at this point that an asdf file with `roman` key is a GDPS datamodel
+        if "roman" in asdf_file.tree:
+            return asdf_file.tree["roman"]
+
         asdf_file.close()
         raise TypeError(f"Unknown datamodel type: {model_type}")

tests/test_open.py

@@ -234,6 +234,7 @@ def test_read_pattern_properties():
         rdm_open(Path(__file__).parent / "data" / "photmjsm.asdf")
 
 
+@pytest.mark.xfail(reason="We currently do not have a way to identify if a datamodel is a GDPS datamodel")
 def test_rdm_open_non_datamodel():
     from roman_datamodels.datamodels import open as rdm_open