$ the-wire · showcase
UNDICI FIXES FLAKY WEBSOCKET TESTS AND DEAD ASSERTIONS
By RepoJournal · Filed · About Node.js · Composed from the cited sources · methodology
3 people shipped this
Undici shipped three critical stability fixes overnight that eliminate unreachable code paths and deterministic test failures across websockets and HTTP dispatching.
The HTTP dispatcher had a dead assertion checking contentLength equality [1] — a condition that could never fail because writeH1 and writeH2 already normalize the value before invoking writeBlob. Killing dead code matters because it reduces cognitive load on maintainers and prevents future bugs hiding in unreachable branches. Meanwhile, the websocket test suite was leaking race conditions [2] that made send tests flaky; the fix refactors to async/await with proper cleanup registration, ensuring deterministic teardown before assertions run. A third patch [3] relaxes Content-Range parsing to accept unknown-size values, fixing a real-world interop issue. Core also landed a SubtleCrypto.supports() accuracy fix [4] that validates ECDH shared-secret output matches requested lengths — this closes a gap where algorithm support claims could be misleading. The crypto desk also optimized normalizeAlgorithm dispatch [5] by replacing O(n) case-insensitive scans with O(1) SafeMap lookups, a hot-path win for workloads calling crypto methods repeatedly.
Action items
- → Test your websocket implementation against latest undici — the flaky test fixes may surface real issues you've been masking nodejs/undici [plan]
- → Verify Content-Range handling in your HTTP clients if serving range requests [ref:4] nodejs/undici [monitor]
- → Audit SubtleCrypto.supports() calls if you're relying on ECDH algorithm support detection nodejs/node [monitor]
References
- [1] fix(dispatcher): remove unreachable assert in writeBlob (#5231) ↗ nodejs/undici
- [2] test(websocket): fix flaky send test ↗ nodejs/undici
- [3] fix: accept unknown-size Content-Range values ↗ nodejs/undici
- [4] crypto: improve accuracy of SubtleCrypto.supports ↗ nodejs/node
- [5] crypto: optimize normalizeAlgorithm dispatch hot path ↗ nodejs/node
