fix: Detect clean-session reconnects in Subscription::next_message#81
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KennethKnudsen97 merged 2 commits intoMay 4, 2026
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Track clean-session reconnects via `clean_session_count: u8` on `Shared`, bumped in `set_connected` only when `connected == Some(false)`. `Subscription` snapshots the counter at creation; `poll_next` returns `None` if the live counter has advanced — i.e. the broker has dropped our subs since this subscription was created. Replaces the previous `clean_session()` future. That code snapshotted `prev_state` inside a future built fresh on every `poll_next` and acquired the lock *after* `set_connected` released it, so `prev_state` always equalled the post-mutation `shared.connected`. The pattern `(None | Some(true), Some(false))` was structurally unreachable. Transient disconnects and session-resume reconnects do not bump the counter — broker-side and local subscriber state are intact, so the subscription stays valid. Refs FactbirdHQ/rustot#121
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MathiasKoch
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May 4, 2026
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Summary
clean_session_count: u8onShared, bumped inset_connectedonly whenconnected == Some(false).Subscriptionsnapshots the counter at creation;poll_nextreturnsNoneif the live counter has advanced.clean_session()future, which was structurally unable to observe the transition (see below).Why the old code didn't work
clean_session()snapshottedprev_stateinside a fresh future built on everypoll_next. The future acquired the lock afterset_connectedreleased it, soprev_statealways equalled the post-mutationshared.connected. The pattern(None | Some(true), Some(false))was never reachable — the "before" half of the comparison was dead-on-arrival.Test plan
next_message().await → None, callers resubscribe.Refs FactbirdHQ/rustot#121