application/pdf doesn't work

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• 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 (example)

Description

This is a similar issue to https://github.com/OpenAPITools/openapi-generator/issues/2035

Instead of text/plain not being handled, it's application/pdf that isn't handled. The response comes back perfectly fine from the API (works in postman and I see it in dev tools). However, once it goes through the generated code, the response get's wiped out and set to undefined. My hunch is that because the responseType is set to json opposed to 'blob'

Generated code

/**
     * @param id 
     * @param observe set whether or not to return the data Observable as the body, response or events. defaults to returning the body.
     * @param reportProgress flag to report request and response progress.
     */
    public downloadReportAsync(id?: string, observe?: 'body', reportProgress?: boolean, options?: {httpHeaderAccept?: 'application/pdf'}): Observable<object>;
    public downloadReportAsync(id?: string, observe?: 'response', reportProgress?: boolean, options?: {httpHeaderAccept?: 'application/pdf'}): Observable<HttpResponse<object>>;
    public downloadReportAsync(id?: string, observe?: 'events', reportProgress?: boolean, options?: {httpHeaderAccept?: 'application/pdf'}): Observable<HttpEvent<object>>;
    public downloadReportAsync(id?: string, observe: any = 'body', reportProgress: boolean = false, options?: {httpHeaderAccept?: 'application/pdf'}): Observable<any> {

        let queryParameters = new HttpParams({encoder: this.encoder});
        if (id !== undefined && id !== null) {
          queryParameters = this.addToHttpParams(queryParameters,
            <any>id, 'id');
        }

        let headers = this.defaultHeaders;

        let httpHeaderAcceptSelected: string | undefined = options && options.httpHeaderAccept;
        if (httpHeaderAcceptSelected === undefined) {
            // to determine the Accept header
            const httpHeaderAccepts: string[] = [
                'application/pdf'
            ];
            httpHeaderAcceptSelected = this.configuration.selectHeaderAccept(httpHeaderAccepts);
        }
        if (httpHeaderAcceptSelected !== undefined) {
            headers = headers.set('Accept', httpHeaderAcceptSelected);
        }


        let responseType: 'text' | 'json' = 'json';  // <-- Issue seems to be here
        if(httpHeaderAcceptSelected && httpHeaderAcceptSelected.startsWith('text')) {
            responseType = 'text';
        }

        return this.httpClient.get<object>(`${this.configuration.basePath}/api/testing`,
            {
                params: queryParameters,
                responseType: <any>responseType, // <-- should be 'blob' but ends up as 'json'
                withCredentials: this.configuration.withCredentials,
                headers: headers,
                observe: observe,
                reportProgress: reportProgress
            }
        );
    }

openapi-generator version

4.3.1

OpenAPI declaration file content or url

"/api/testing": {
      "get": {
        "tags": [
          "SomeTag"
        ],
        "operationId": "DownloadAsync",
        "parameters": [
          {
            "name": "id",
            "in": "query",
            "schema": {
              "type": "string",
              "nullable": true
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/pdf": {
                "schema": {
                  "$ref": "#/components/schemas/File"
                }
              }
            }
          }
        }
      }
    },

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

It looks like a fix has been suggested in similar issue (https://github.com/OpenAPITools/openapi-generator/issues/11494). However, it would be nice to have this functionality work out of the box. If there was a way to allow a response type to be passed in, I think it would work just fine.

Start with the generated Angular client method shown in the issue and the OpenAPI declaration for /api/testing, then trace how the generator selects the response type for application/pdf. Reproduce the generated client behavior and confirm completion when a PDF response remains available instead of becoming undefined.