[TypeScript-Fetch] Return type for non-parsed endpoints should be Response

[masaeedu]

Description

The TypeScript fetch client currently falls back to returning a Promise<any> in cases where the spec does not dictate a schema for the response.

At runtime, what it's actually returning is a fetch API Response, which needs to be consumed buffer by buffer, or turned into text or something before the request can actually be considered complete.

The any being returned provides no indication of this, so users can end up misusing the API by simply awaiting the Promise<any> (which only represents the start of the response), and expecting that server is done talking to them.

Swagger-codegen version

Present in master:

swagger-codegen/modules/swagger-codegen/src/main/resources/typescript-fetch/api.mustache

Line 256 in 4d994a2

{{nickname}}({{#allParams}}{{paramName}}{{^required}}?{{/required}}: {{{dataType}}}, {{/allParams}}options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<{{#returnType}}{{{returnType}}}{{/returnType}}{{^returnType}}any{{/returnType}}> {

Swagger declaration file content or url

Docker API spec

Command line used for generation

generate -i /moby/api/swagger.yaml -l typescript-fetch -o /package

Suggest a fix/enhancement

The return type should be changed to Promise<Response> (the Response type is built in to lib.d.ts), to make it clear to users of the fetch API that they still need to .json() or .text() the response and await the resulting promise.