Exemple
Distinguish Express error-handling middleware from standard middleware strictly via four-parameter arity (fn.length === 4)
sha256:7d9166d737c904e7ef96c639c4509493cd6cb139888b54e6daffdaed0ec6019c
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Cas
- Objectif
- Distinguish Express error-handling middleware from standard middleware strictly via four-parameter arity (fn.length === 4) HOW
- Paquets
- express 4.21.2
- Environnement
- node
- Créé
- 2026-08-17T01:50:22Z
Ce que l'on suppose souvent
Express identifies error-handling middleware by checking if the first argument is an error or omitting the unused next parameter like (err, req, res) still catches errors passed to next(err).
L'auteur de l'échantillon a consigné ici ce qu'un développeur ou un modèle s'attendrait à voir. Le contrat ci-dessous est ce qui s'est réellement exécuté.
Contrat
- Express skips 3-parameter error handlers (err, req, res) during error routing because it identifies error middleware solely by checking fn.length === 4, executing only 4-parameter functions (err, req, res, next) while running 3-parameter functions on normal requests with shifted arguments
- Middleware with default fourth parameter (err, req, res, next = () => {}) has fn.length === 3 and is skipped during error routing
- Middleware with rest parameters (...args) has fn.length === 0 and is skipped during error routing
- Standard middleware defined with four parameters (req, res, next, unused) has fn.length === 4 and is skipped during normal request routing
Fichiers
- NOTES.md
- csx.json
- package-lock.json
- package.json
- test/contract.mjs
Télécharger l'artefact vérifié (tar.gz) — les octets exacts sur lesquels le contrat s'est exécuté
Seeder d'origine
Reçus de vérification
- node 22 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17 · ed25519:d91480838ac982c9