From 38f9d8046c7e2172ec4da3a1fb40c98689895fd2 Mon Sep 17 00:00:00 2001 From: Ethan Dalool Date: Mon, 14 Mar 2022 15:32:11 -0700 Subject: [PATCH] Add worms.raise_without_rollback. --- voussoirkit/worms.py | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/voussoirkit/worms.py b/voussoirkit/worms.py index 2d66478..2aed612 100644 --- a/voussoirkit/worms.py +++ b/voussoirkit/worms.py @@ -26,14 +26,28 @@ class DeletedObject(WormException): ''' pass +# snake-cased because I want the ergonomics of a function from the caller's end. +class raise_without_rollback: + def __init__(self, exc): + self.exc = exc + def slice_before(li, item): index = li.index(item) return li[:index] def transaction(method): ''' - Open a savepoint before running the method. - If the method fails, roll back to that savepoint. + This decorator can be added to functions that modify your worms database. + A savepoint is opened, then your function is run, then we roll back to the + savepoint if an exception is raised. + + This decorator adds the keyword argument 'commit' to your function, so that + callers can commit it immediately. + + If you want to raise an exception without rolling back, you can return + worms.raise_without_rollback(exc). This could be useful if you want to + preserve some kind of attempted action in the database while still raising + the action's failure. ''' @functools.wraps(method) def wrapped_transaction(self, *args, commit=False, **kwargs): @@ -52,9 +66,17 @@ def transaction(method): database.rollback(savepoint=savepoint_id) raise + if isinstance(result, raise_without_rollback): + raise result.exc from result.exc + if commit: database.commit(message=method.__qualname__) elif not is_root: + # In order to prevent a huge pile-up of savepoints when a + # @transaction calls another @transaction many times, the sub-call + # savepoints are removed from the stack. When an exception occurs, + # we're going to rollback from the rootmost savepoint anyway, we'll + # never rollback one sub-transaction. database.release_savepoint(savepoint=savepoint_id) return result