Rcal 596 Updates for association processing

CHANGES.rst

@@ -1,5 +1,8 @@
 0.17.0 (unreleased)
 ===================
+
+- Add checks for for association processing [#241]
+
 - Make a shallow copy when opening an existing datamodel, rather than
   a full copy.  [#232]
 

src/roman_datamodels/datamodels/_utils.py

@@ -3,6 +3,7 @@
     the open/factory function for creating datamodels
 """
 import warnings
+from pathlib import Path
 
 import asdf
 from astropy.utils import minversion
@@ -93,5 +94,14 @@ 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)
 
+        if isinstance(init, str):
+            exts = Path(init).suffixes
+            if not exts:
+                raise ValueError(f"Input file path does not have an extension: {init}")
+
+            # Assume json files are asn and return them
+            if exts[0] == "json":
+                return init
+
         asdf_file.close()
         raise TypeError(f"Unknown datamodel type: {model_type}")