[BUG] [typescript-fetch] Not able to generate a `BlobApiResponse` with a binary response

[FabianWilms]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request: My company sponsors openapi-generator https://opencollective.com/itm

Description

Hello,

I'm currently trying to generate a typescript api client in which one endpoint should deliver a blob as an API response. But no matter how I define the endpoint in my API spec, the client always tries to convert it to a string.

I followed the recommendation when modelling binary responses by using return type string with format binary but that doesn't work.

It will generate the correct return type for the methods:

Promise<runtime.ApiResponse<Blob>>

But it wrongly tries to convert the response to a text instead of a blob.

openapi-generator version

7.14.0

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Sample Attachment API
  version: '1.0'
paths:
  /attachment:
    get:
      operationId: getAttachment
      responses:
        default:
          description: Attachment as binary data.
          content:
            application/octet-stream:
              schema:
                type: string
                format: binary

Generation Details

java -jar openapi-generator-cli.jar generate -i api-docs/test-docs.yaml -g typescript-fetch -o src/test-api

Steps to reproduce

1. generate
2. look at apis/DefaultApi.ts

        if (this.isJsonMime(response.headers.get('content-type'))) {
            return new runtime.JSONApiResponse<Blob>(response);
        } else {
            return new runtime.TextApiResponse(response) as any;
        }

What should actually be generated is

        return new runtime.BlobApiResponse(response);

Related issues/PRs

Suggest a fix

Looking at the template https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/typescript-fetch/apis.mustache#L341 I can see the function I need to be generated is already there - but I haven't found a way to trigger the isResponseFile flag with my config.

Either I have a wrong api spec - in this case I would be very happy to be led in the right direction to fix it.

Or the generator has a bug in this case.