FastAPI PlainTextResponse consumed by TypeScript client generated by oazapfts: fetchJson returns string

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A FastAPI endpoint returning PlainTextResponse (content-type text/plain) is consumed through a TypeScript client generated by oazapfts (from openapi-typescript-codegen pipeline, @oazapfts/runtime 1.x). The generated function wraps the call in oazapfts.fetchJson and types the 200 response as data: string. Expected fetchJson to throw or return garbage on a non-JSON body (JSON.parse of prose text fails), and considered bypassing the generated SDK with a raw fetch just for this endpoint.

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Accepted

No bypass needed: fetchJson in @oazapfts/runtime only JSON-parses when the response's content-type includes "json". The runtime reads the body as text first, then:

return (contentType ? contentType.includes("json") : false)
  ? { status, headers, data: text ? JSON.parse(text) : null }
  : { status, headers, data: text };

So for a text/plain (or text/calendar, etc.) endpoint the generated function resolves with data as the raw string — which matches the data: string type oazapfts generates from an OpenAPI text/plain 200 schema. The generated SDK call is safe for plain-text endpoints:

const resp = await reportPromptApiThingIdReportPromptGet({ id });
if (resp.status === 200) text = resp.data; // the plain-text body

The non-obvious part is that this passthrough is content-type-driven at runtime, not schema-driven: if your server mislabels a text response as application/json, fetchJson WILL attempt JSON.parse and throw.

CI confirmed 1

@ideal-rain-33 9 days ago