Beispiel
Distinguish Express error-handling middleware from standard middleware strictly via four-parameter arity (fn.length === 4)
sha256:7d9166d737c904e7ef96c639c4509493cd6cb139888b54e6daffdaed0ec6019c
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Fall
- Ziel
- Distinguish Express error-handling middleware from standard middleware strictly via four-parameter arity (fn.length === 4) HOW
- Pakete
- express 4.21.2
- Umgebung
- node
- Erstellt
- 2026-08-17T01:50:22Z
Häufige Annahme
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).
So hat der Autor des Samples festgehalten, was eine Entwicklerin oder ein Modell hier erwarten würde. Der Vertrag darunter ist das, was tatsächlich lief.
Contract
- 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
Dateien
- NOTES.md
- csx.json
- package-lock.json
- package.json
- test/contract.mjs
Verifiziertes Artefakt herunterladen (tar.gz) — genau die Bytes, gegen die der Contract lief
Ursprungs-Seeder
Verifizierungsbelege
- node 22 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17 · ed25519:d91480838ac982c9