fix: raise DeserializationError for unimportable classes

haystack/utils/base_serialization.py

@@ -269,7 +269,11 @@ def _deserialize_value(value: dict[str, Any]) -> Any:
     payload = value["data"]
 
     # Custom class where value_type is a qualified class name
-    cls = import_class_by_name(value_type)
+    # ValueError covers type names without a module prefix, which import_class_by_name cannot split
+    try:
+        cls = import_class_by_name(value_type)
+    except (ImportError, ValueError) as e:
+        raise DeserializationError(f"Class '{value_type}' not correctly imported") from e
 
     # try from_dict (e.g. Haystack dataclasses and Components)
     if hasattr(cls, "from_dict") and callable(cls.from_dict):

releasenotes/notes/fix-deseri-import-class-5d22bc73b2089ecb.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed ``_deserialize_value_with_schema`` raising ``ImportError`` instead of ``DeserializationError``
+    when a snapshot references a class that can no longer be imported.

test/utils/test_base_serialization.py

@@ -423,6 +423,20 @@ def test_deserialize_value_with_wrong_value():
         )
 
 
+def test_deserialize_value_with_schema_class_not_importable():
+    with pytest.raises(
+        DeserializationError, match="Class 'test_base_serialization.NonExistentClass' not correctly imported"
+    ):
+        _deserialize_value_with_schema(
+            {"serialization_schema": {"type": "test_base_serialization.NonExistentClass"}, "serialized_data": {}}
+        )
+
+
+def test_deserialize_value_with_schema_class_name_without_module():
+    with pytest.raises(DeserializationError, match="Class 'NonExistentClass' not correctly imported"):
+        _deserialize_value_with_schema({"serialization_schema": {"type": "NonExistentClass"}, "serialized_data": {}})
+
+
 def test_serialize_and_deserialize_pydantic_model():
     model_instance = CustomModel(id=1, name="Test")
     serialized = _serialize_value_with_schema(model_instance)