fix: return correct message when validation error occurs

src/fusor/fusor.py

@@ -45,7 +45,7 @@
     UnknownGeneElement,
 )
 from fusor.nomenclature import generate_nomenclature
-from fusor.tools import translate_identifier
+from fusor.tools import get_error_message, translate_identifier
 
 _logger = logging.getLogger(__name__)
 
@@ -178,11 +178,7 @@ def categorical_fusion(
                 regulatoryElement=regulatory_element,
             )
         except ValidationError as e:
-            error_message = (
-                str(e.errors()[0]["msg"])
-                if e.errors() and "msg" in e.errors()[0]
-                else str(e)
-            )
+            error_message = get_error_message(e)
             raise FUSORParametersException(error_message) from e
         return fusion
 
@@ -214,11 +210,7 @@ def assayed_fusion(
                 readingFramePreserved=reading_frame_preserved,
             )
         except ValidationError as e:
-            error_message = (
-                str(e.errors()[0]["msg"])
-                if e.errors() and "msg" in e.errors()[0]
-                else str(e)
-            )
+            error_message = get_error_message(e)
             raise FUSORParametersException(error_message) from e
         return fusion
 

src/fusor/tools.py

@@ -9,6 +9,7 @@
 from gene.database import AbstractDatabase as GeneDatabase
 from gene.database import create_db
 from gene.schemas import CURIE
+from pydantic import ValidationError
 
 from fusor.exceptions import IDTranslationException
 
@@ -89,3 +90,14 @@ async def check_data_resources(
     return FusorDataResourceStatus(
         cool_seq_tool=all(cst_status), gene_normalizer=gene_status
     )
+
+
+def get_error_message(e: ValidationError) -> str:
+    """Get the specific error message from a pydantic ValidationError
+
+    :param e: the ValidationError to get the message from
+    :return: extracted error message or the string representation of the exception if 'msg' field is not present
+    """
+    return (
+        str(e.errors()[0]["msg"]) if e.errors() and "msg" in e.errors()[0] else str(e)
+    )