Switch PersistenceNotifierGuard persist closure to FnOnce #3835
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This allows us to move owned and mutable values into the closure, with the assumption that the closure can only be invoked once. As a result, we now have to track `should_persist` as an `Option`, such that we can `take` the owned closure and invoke it within the `PersistenceNotifierGuard::drop` implementation.
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## main #3835 +/- ##
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- Coverage 89.92% 89.84% -0.09%
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Branches 129581 129655 +74
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| event_persist_notifier: &'a Notifier, | ||
| needs_persist_flag: &'a AtomicBool, | ||
| should_persist: F, | ||
| should_persist: Option<F>, |
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The explanation why this needs to be an option could be helpful in the code rather than in the commit message.
| @@ -2815,10 +2815,10 @@ enum NotifyOption { | |||
| /// We allow callers to either always notify by constructing with `notify_on_drop` or choose to | |||
| /// notify or not based on whether relevant changes have been made, providing a closure to | |||
| /// `optionally_notify` which returns a `NotifyOption`. | |||
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Background question: it seems that in some instances, the persist_check isn't just checking, but also making the actual changes to the chan mgr state. Is that fine, or indicative of the PersistenceNotifierGuard not fully matching its desired use cases?
| @@ -2833,20 +2833,20 @@ impl<'a> PersistenceNotifierGuard<'a, fn() -> NotifyOption> { | |||
| /// isn't ideal. | |||
| fn notify_on_drop<C: AChannelManager>( | |||
| cm: &'a C, | |||
| ) -> PersistenceNotifierGuard<'a, impl FnMut() -> NotifyOption> { | |||
| ) -> PersistenceNotifierGuard<'a, impl FnOnce() -> NotifyOption> { | |||
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So this means that only single-use closure may be provided now. And it seems we are lucky that nowhere a closure was reused, so no other refactoring needed? (questions for me to understand this better)
| fn drop(&mut self) { | ||
| match (self.should_persist)() { | ||
| match (self.should_persist.take().unwrap())() { |
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We should never reach this, but how about avoiding the unwrap and just matching on Some(..)/None?
This allows us to move owned and mutable values into the closure, with the assumption that the closure can only be invoked once. As a result, we now have to track
should_persistas anOption, such that we cantakethe owned closure and invoke it within thePersistenceNotifierGuard::dropimplementation.Motivated by #3736 (comment).