fix: Add exception to the typing-only Details dictionary for cases when on_exception is used

Author: edgarrmondragon

CHANGELOG.md

@@ -8,6 +8,7 @@
 - Adapt test cases to pytest-asyncio 1.0 compatibility https://github.com/python-backoff/backoff/pull/1 from @pastalian
 - Include tests in source distribution https://github.com/python-backoff/backoff/pull/13
 - Added `logging.LoggerAdapter` to `_MaybeLogger` union https://github.com/python-backoff/backoff/pull/34 from @jcbertin
+- Add `exception` to the typing-only `Details` dictionary for cases when `on_exception` is used https://github.com/python-backoff/backoff/pull/35
 
 ### Packaging
 

backoff/_typing.py

@@ -27,6 +27,7 @@ class _Details(TypedDict):
 class Details(_Details, total=False):
     wait: float  # present in the on_backoff handler case for either decorator
     value: Any  # present in the on_predicate decorator case
+    exception: Exception  # present in the on_exception decorator case
 
 
 T = TypeVar("T")