fix: [MTS-3020] derive content types from OpenAPI 3.0 requestBody/response content

[granojaakko]

Problem

Clients generated from OpenAPI 3.0 specs send application/json for every endpoint, even ones the spec declares as XML (or any other media type).

Concretely: the cXML PunchOut Order Request tool in ecom-admin posts to POST /v2/cxml/punchout, which the spec declares as application/xml. The generated client instead sent Content-Type: application/json with the cXML JSON.stringify'd into a string. ecom-api's global express.json() parser then tried to JSON.parse the XML and returned a 400 (Unexpected token '"', ""<?xml ver"... is not valid JSON) before any cXML handler ran.

Root cause

OpenAPI 3.0 carries request/response media types under requestBody.content and responses[code].content. The 3.0 support (added in "feat: add openapi 3.0 support") read those maps only to extract the JSON schema, and never set op.contentTypes / op.accepts. The only code paths that populate those are the Swagger 2.0 consumes / produces fields — absent in 3.0 — so every operation fell through to the application/json default in spec.ts.

Fix

• src/spec/operations.ts: populate contentTypes from requestBody.content media types, and accepts from the success (2xx) response content media types.
• src/gen/js/genOperations.ts: emit accepts only when it's not the application/json default, so existing JSON clients regenerate byte-identically (no churn).

Impact / blast radius

Consumers: ecom-admin, ecom-storefront, ecom-order-synchronizer (all on the same pin). On regeneration:

• JSON endpoints (the vast majority — 64 request / 166 response bodies in the current ecom-api spec): byte-identical output.
• XML endpoints (cXML: 2 request, 3 response bodies): corrected to application/xml — this is the fix.
• multipart/form-data (uploadEditorTemplate, 1 endpoint): flips to multipart/form-data. It is not called by application code in any of the three consumers (dead generated stub), so no runtime impact.

Testing

• Added an OpenAPI 3.0 fixture (test/openapi3.yml) and 4 cases covering XML request/response derivation, a JSON control, and independent request/response types. Verified they fail against the unpatched parser and pass with the fix.
• Verified end-to-end by npm link-ing this branch into ecom-admin and running npm run apigen:file: punchOutOperation now generates contentTypes: ['application/xml'], accepts: ['application/xml']; JSON ops unchanged.

Rollout

After merge, bump the openapi-client pin in ecom-admin, ecom-storefront, and ecom-order-synchronizer, regenerate their clients, and deploy. Worth a glance at each regen diff before deploying.

[Copilot]

Pull request overview

This PR fixes OpenAPI 3.0 media type handling by deriving per-operation request contentTypes (from requestBody.content) and response accepts (from 2xx responses[code].content), preventing clients from defaulting everything to application/json when the spec declares XML (or other) media types.

Changes:

• Populate op.contentTypes from OpenAPI 3.0 requestBody.content keys and op.accepts from 2xx response content keys.
• Adjust JS operation codegen to omit emitting accepts when it’s the default ['application/json'] (avoids churn for existing JSON-only clients).
• Add an OpenAPI 3.0 fixture and tests covering XML, JSON control, and mixed request/response media types.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/spec/operations.spec.ts	Adds assertions verifying OpenAPI 3.0 request/response media type derivation.
test/openapi3.yml	New OpenAPI 3.0 fixture exercising XML/JSON/mixed content negotiation.
src/spec/operations.ts	Derives contentTypes/accepts from OpenAPI 3.0 content maps (requestBody + 2xx responses).
src/gen/js/genOperations.ts	Avoids emitting accepts when it is only application/json to keep output stable.
dist/spec/operations.js	Built artifact reflecting the updated OpenAPI 3.0 parsing behavior.
dist/gen/js/genOperations.js	Built artifact reflecting the updated codegen emission rules for accepts.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.