🐛 Unify halt around signal + observe scope.destroyed (#1159, #1160)#1167
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🐛 Unify halt around signal + observe scope.destroyed (#1159, #1160)#1167cowboyd wants to merge 2 commits into
cowboyd wants to merge 2 commits into
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In order to implement critical sections that cannot be interrupted and that are also able to implement sticky return, we need to make the behavior of the reducer more context sensitive. This drops the whole validation behavior and instead completely inverts control over iteration to the delimiter from the reducer. Now, the reducer becomes a pure iterator-stepping engine. The delimiter can tell it to use "next", "return", "throw" to tell it how to advance the iterator, or it can even tell it "drop" to ignore the dequeued item entirely.
There were multiple pathways for signaling a halt and then awaiting its consequence. This unifies all of them by interrupting the current delimiter, and then awaiting a single future representing the destruction of the scope. Now, `task.halt()` collapses to this pattern. This eliminates the dual-routine pattern that gave rise to both #1159 and #1160
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Motivation
Fix #1159 and #1160
task.halt()had two surfaces (Promise and Operation), and the Promise surface spawned a second routine viaowner.run(destroy)to drive teardown. This second task raced the original task's own routine for control of the same delimiter. This resulted in incorrect teardown sequencing.#1153 and #1154 remain open — they're a different class of fix (sticky-return semantics + capturing
iter.return's done value), substantially easier on this substrate but out of scope here.Approach
task.halt()collapses to a single signal-and-observe pair. We lazily calltop.interrupt()and then join onscope.destroyed. The task's own routine drives unwinding via its existingtry { yield* top } finally { yield* destroy() }, so all the work happens in the original routine. With one pathway, there is no possibility for a race.Alternates
We tried keeping both surfaces with #1155, and just "synchronize them harder", but the problem is the secord routine itself.
TODO:
Future Direction
Eventually, We'll actually move the signal and halting logic entirely into the scope, using an async like abort signal, so that
task.halt()just becomes lazysignal.abort()