fix(firestore): dedupe listenForChanges subscriptions to prevent crash#2257
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fix(firestore): dedupe listenForChanges subscriptions to prevent crash#2257cursor[bot] wants to merge 1 commit into
cursor[bot] wants to merge 1 commit into
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…sed event bus Repeated invokeAPI calls with listenForChanges: true accumulated Firestore snapshot listeners because subscribeToApi always appended to a list. Replace the prior subscription for the same apiName (matching SSE provider behavior) and skip callbacks after provider dispose. Also ignore binding dispatches once the page event bus is closed, which avoids crashes when a snapshot arrives after Page dispose but before Screen cancels API providers. Co-authored-by: Sharjeel Yunus <sharjeelyunus@users.noreply.github.com>
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Bug and impact
Trigger: A screen calls the same Firestore API with
listenForChanges: truemore than once (e.g. on tab switches, navigation callbacks, or screen refreshes). Each call adds another snapshot listener without cancelling the previous one.Impact: After ~8–15 Firestore updates, callbacks multiply exponentially, the app slows dramatically, and can crash. Navigating away can also crash with
Bad state: Cannot add new events after calling closewhen a snapshot arrives after the page event bus is destroyed but before the screen cancels API providers.Fixes #2253.
Root cause
FirestoreAPIProvider.subscribeToApi()appended every subscription to aList<StreamSubscription>with no deduplication by API name (unlikeSSEAPIProvider, which replaces existing subscriptions).EventBusbeforeScreen.dispose()cancels Firestore listeners, so late snapshot callbacks attempted to dispatch binding updates on a closed bus.Fix
Map<String, StreamSubscription>keyed byapiNameand cancel/replace any existing subscription before subscribing (mirrors SSE provider behavior).Validation
modules/ensemble/test/firestore_listen_dedup_test.dartcovering subscription replacement and closed event-bus behavior.modules/ensemble:flutter test test/firestore_listen_dedup_test.dartDuplicate check
cursor/critical-bug-remediation-0747): TabController zero-length crash — different code path.unsubscribe-changes): attempted Firestore unsubscribe via singleton +unSubscribeToApi; closed without merge; did not guard event-bus dispose race.cursor/critical-bug-remediation-adc5: TabController fix only.