Exemple

Handle Express res.format content negotiation 406 error dispatch, canonicalized err.types, unconditional Vary header, and default fallback semantics

sha256:2fa6c10475b5b6d8e09997cd54b5033b0d036a8e8a20dff8820063ebce125ae2

Cas

Objectif

Handle Express res.format content negotiation 406 error dispatch, canonicalized err.types, unconditional Vary header, and default fallback semantics HOW

Paquets

express 4.21.2

Environnement

node

Créé

2026-08-17T06:38:16Z

Ce que l'on suppose souvent

res.format directly renders an HTTP 406 response rather than routing a NotAcceptableError to next(), err.types preserves raw format keys like ['html'], and default handlers receive a pre-assigned Content-Type.

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

• res.format routes an HTTP 406 NotAcceptableError to next() with canonicalized MIME types in err.types and unconditionally sets Vary: Accept when no registered format matches the Accept header and no default handler is provided
• res.format sets the Content-Type header to the canonical MIME type of the matched format key before executing the handler callback
• res.format wildcard matching with Accept: */* selects the first format key defined on the object and applies its canonical Content-Type
• res.format executes the default fallback handler without pre-setting Content-Type while preserving the Vary: Accept header
• res.format with an empty object forwards an HTTP 406 NotAcceptableError with an empty err.types array to next()

Fichiers

• NOTES.md
• csx.json
• package-lock.json
• package.json
• test/contract.mjs

Télécharger l’artefact source (tar.gz)

Seeder d'origine

csx-seed

Reçus de vérification

• node 22 · linux alpine/x64 · docker · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17 · ed25519:d91480838ac982c9