🐛 fix resource timing buffer listener not stopped on cleanup

[thomas-lebeau]

Motivation

The manageResourceTimingBufferFull function registers a listener for the resourcetimingbufferfull event on the performance object. However, the return value (a cleanup function) was not being captured or called when the PerformanceObservable was cleaned up, causing the listener to remain active after the observer was disconnected.

ERROR LOG: 'Datadog Browser SDK:', 'Leaked listener
  event names: "resourcetimingbufferfull"
  attached with: "longTaskCollection when browser only supports legacy longtask should collect when trackLongTasks=true"
  executed outside of a spec
  attachment stack: Error
    at withLeakDetection (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:101294:53)
    at EventTarget.addEventListener (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:101264:55)
    at http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:12854:16
    at Array.forEach (<anonymous>)
    at addEventListeners (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:12851:14)
    at addEventListener (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:12802:10)
    at manageResourceTimingBufferFull (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:130856:111)
    at Observable.onFirstSubscribe (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:130813:5)
    at Observable.addObserver (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:59876:66)
    at Observable.subscribe (http://localhost:9876/absolute/tmp/_karma_webpack_163552/commons.js?24aece18a060ffd3181f9013588a77285834b230:59849:10)'

Additionally, resourceTimingBufferFullListener was typed as non-nullable, which prevented proper cleanup and reset of the module-level variable.

Changes

• Capture the return value of manageResourceTimingBufferFull and call it in the cleanup callback of createPerformanceObservable
• Reset resourceTimingBufferFullListener to undefined after stopping it, so subsequent calls can re-register the listener if needed
• Fix the type of resourceTimingBufferFullListener to | undefined to reflect its actual nullable state

Test instructions

1. Initialize the RUM SDK
2. Stop the SDK (triggering cleanup)
3. Verify no lingering resourcetimingbufferfull event listeners remain on the performance object

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep shared resource buffer listener alive across observables

Calling stopManageResourceTimingBufferFull() in every createPerformanceObservable cleanup removes the single module-level resourcetimingbufferfull listener even when other performance observables are still subscribed. This is reachable with short-lived subscriptions like createPageActivityObservable (unsubscribed when waitPageActivityEnd completes), while long-lived resource collection remains active, so the resource timing buffer is no longer cleared and later resource entries can be dropped once full. The cleanup needs ref-counting (or equivalent) so the shared listener is only removed when the last dependent observable stops.

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