Fix ClassInitError crashing instead of reporting a missing class

lume/serializers/base.py

@@ -1,11 +1,20 @@
 from abc import ABC, abstractmethod
 
 
+def _module_base(module_name):
+    """Top-level package name from a dotted module string.
+
+    Accepts a module object as well, so the error path never crashes on a
+    caller that passes the imported module instead of its name.
+    """
+    name = getattr(module_name, "__name__", module_name)
+    return str(name).split(".")[0]
+
+
 class ModuleImportError(Exception):
     def __init__(self, module_name, module_version):
         self.module_name = module_name
-        module_base = module_name.split(".")[0]
-        module_version = module_version
+        module_base = _module_base(module_name)
         self.message = (
             f"Unable to import module {module_name}. Object was serialized with {module_version}. "
             f"Is a compatible version of {module_base} installed?"
@@ -17,7 +26,7 @@ class ClassInitError(Exception):
     def __init__(self, class_name, module_name, module_version):
         self.module_name = module_name
         self.class_name = class_name
-        module_base = module_name.split(".")[0]
+        module_base = _module_base(module_name)
         self.message = (
             f"Unable to get {class_name} from {module_name}. Object was serialized with {module_version}. "
             f"Is a compatible version of {module_base} installed?"

lume/serializers/hdf5.py

@@ -77,10 +77,10 @@ def deserialize(cls, filename: str) -> "Base":
             except ImportError:
                 raise ModuleImportError(package_str, package_version)
 
-            object_type = getattr(object_import_module, object_name)
+            object_type = getattr(object_import_module, object_name, None)
 
-            if not object_type:
-                raise ClassInitError(object_name, object_import_module, package_version)
+            if object_type is None:
+                raise ClassInitError(object_name, package_str, package_version)
 
             object = object_type()
             object.load_archive(f)