keithamus/observable-polyfill

tearDown order needs to be upstream->downstream on consumer-initiated unsubscription

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#30 opened on Jul 30, 2025

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Description

About

  • wpt test "Teardowns are called in upstream->downstream order on consumer-initiated unsubscription" fails

Expected behavior

  • tearDown order:
    • "upstream abort handler"
    • "upstream teardown. reason: Abort!"
    • "middle abort handler"
    • "middle teardown. reason: Abort!"
    • "downstream abort handler"
    • "downstream teardown. reason: Abort!"

Current behavior

  • tearDown order:
    • "downstream abort handler"
    • "middle abort handler"
    • "upstream abort handler"
    • "upstream teardown. reason: Abort!"
    • "middle teardown. reason: Abort!"
    • "downstream teardown. reason: Abort!"

How to reproduce

  • npm run test-serve and inspect wpt test results in the browser

Additional context

https://github.com/keithamus/observable-polyfill/blob/5af5df1b6bb87abc44a773701ebcf64c1d1f25c7/test/wpt/observable-constructor.any.js#L728-L763

Contributor guide

Research direction
Trace the teardown order logic in the polyfill and compare with the WICG spec. Ensure that during consumer initiated unsubscription, teardown callbacks are called upstream first, then downstream.
Tech stack
javascript
Domain
api
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Gitnpm
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70