Add function to assert that an object is an instance of a specific type

src/jcloud_docsgen/utils.py

@@ -82,4 +82,37 @@ def human_readable_list(ls: list, final_separator: str = 'and', quotation_mark:
             _quote(str(obj), quotation_mark) # quote the string representation of the object
             for obj in ls[:-1] # do not include the last element of the list
         ]
-    ) + ' ' + final_separator + ' ' + _quote(str(ls[-1]), quotation_mark)
+    ) + ' ' + final_separator + ' ' + _quote(str(ls[-1]), quotation_mark)
+
+def _list_type_names(types: list[type]) -> list[str]:
+    '''
+    Converts a list of types into a list of their names (``__name__``
+    attribute)
+
+    :param types: The list of types
+    :type types: list[type]
+
+    :return: The list of the names of the types
+    :rtype: list[str]
+    '''
+
+    return [tp.__name__ for tp in types]
+
+def assert_that_is_instance(obj: object, class_or_tuple: Union[type, types.UnionType, tuple[type, ...]]) -> None:
+    if not isinstance(class_or_tuple, Union[type, types.UnionType, tuple]):
+        raise TypeError(f'class_or_tuple: expected \'Union[type, types.UnionType, tuple[type, ...]]\', \'got {type(class_or_tuple).__name__}\'')
+    if not isinstance(obj, class_or_tuple):
+        if isinstance(class_or_tuple, (tuple, types.UnionType)):
+            print('MORE')
+            if isinstance(class_or_tuple, types.UnionType):
+                class_or_tuple = class_or_tuple.__args__
+                print('LIST:', _list_type_names(class_or_tuple))
+            if len(class_or_tuple) > 1:
+                exception_message_expected = 'either '
+            else:
+                exception_message_expected = ''
+            exception_message_expected += human_readable_list(_list_type_names(class_or_tuple), 'or', '\'')
+        else:
+            print('SINGLE')
+            exception_message_expected = '\'' + class_or_tuple.__name__ + '\''
+        raise TypeError(f'expected {exception_message_expected}, got \'{type(obj).__name__}\'')