feat(openapi): interface output + fetch-client profiles

[ALagoni97]

What & why

The CLI is built on Modelina, which emits class-based models with marshal()/unmarshal()/validate() — idiomatic for the AsyncAPI/broker world, but the wrong shape for OpenAPI REST consumers, who expect plain interface types + a thin fetch client (the bar set by openapi-typescript, orval, kubb, heyapi). Today a consumer writes new GetV2TransactionsParameters({...}) and resp.data.items[0].marshal() — non-idiomatic ceremony that makes the tool hard to pick for REST.

This PR lets OpenAPI generate pure interfaces + an optional fetch client, exposed through two profiles (types, client), without forking the engine and without changing AsyncAPI or any broker-protocol output. Class mode stays the default everywhere (fully backward compatible).

How it works

export default {
  inputType: 'openapi',
  inputPath: './openapi.json',
  language: 'typescript',
  profile: 'client', // or 'types'
  generators: []      // explicit generators are appended as overrides
};

• types → interface payloads + interface parameters (with standalone serializers) + headers. No channels/client.
• client → everything in types plus the HTTP fetch client.

Engine

• payloads: new modelType: 'class' | 'interface' (default class). Interface mode drops the TS_COMMON_PRESET { marshalling } + validation presets and sets Modelina modelType: 'interface'.
• parameters: same modelType. Interface mode emits a plain interface + free functions serialize<Name>QueryParameters / serialize<Name>PathParameters / serialize<Name>Url (replacing the class getChannelWithParameters), reusing the exact style/explode logic from the class path. Surfaced via a new parameterFunctions map (mirroring headerFunctions).

HTTP client (interface mode)

JSON.stringify(payload) body, response cast to the interface, URL via serialize<Name>Url(...), plain-interface parameters field, interface + serializer imports. Broker protocols are untouched.

Profiles

profile: 'types' | 'client' on the OpenAPI config, expanded in realizeConfiguration() before validation. Distinct from the existing types preset (simple type aliases) — documented in docs/generators/profiles.md.

Testing

• New unit tests: interface-mode parameter rendering (with snapshot) + both profile expansions.
• Regenerated schemas/*.json + docs from Zod; added docs/generators/profiles.md.
• ✅ npm run build, npm run lint (max-warnings 0), npm test (657 tests) all green.
• ✅ End-to-end codegen generate for both profiles against the runtime OpenAPI spec — output type-checks under tsc --strict.

Not included (with reasons)

• Blackbox fixture: the blackbox harness only loads asyncapi/jsonschema documents (no OpenAPI branch) and runs every config × every schema — an OpenAPI config there would break the suite. Validated the same thing directly with tsc --strict on generated output instead.
• Runtime suite / playground iterate: require Docker brokers / the platform checkout. The runtime codegen-openapi.mjs still uses class mode (unchanged, so broker regression gates pass); promoting hand-written interface output to a runtime check is the natural follow-up.

Note for reviewers

Profiles currently prepend their generators and treat explicitly-listed generators as appended overrides. If you'd prefer profiles be all-or-nothing (reject stray generators), that's a small change.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
the-codegen-project	Ready	Preview, Comment	Jul 16, 2026 3:27pm
the-codegen-project-mcp	Ready	Preview, Comment	Jul 16, 2026 3:27pm