[BUG][TypeScript] Description

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

My webservice can return 'text/csv' in case of success or 'application/problem+json' in case of failure. The generated http request only keeps the json Accept header so that the response cannot be interpreted when csvc is returned in case of success.
Therefore the requests results in a "SyntaxError: Unexpected token T in JSON at position 0 at JSON.parse ()" since it is not JSON.
As a workaround, I will wrap my csv in a json.

openapi-generator version

4.3.1
not tested on previous versions

OpenAPI declaration file content or url

    responses:
        "200":
          content:
            text/csv:
              schema:
                type: string
        '404':
          content:
            "application/problem+json":
              schema:
                $ref: "#/components/schemas/Problem"

Command line used for generation

openapi-generator generate -i ./src/apis/contracts/swagger_0.4.yaml -g typescript-angular -o ./src/apis/name --api-package api --model-package model --additional-properties="ngVersion=7.2.11" --additional-properties="withInterfaces=true"

Steps to reproduce

• creates a WS that can return both csv or json
• call the service so it returns csv

Related issues/PRs

not found

Suggest a fix

I guess there is a reason why, but in the generated code, only the json accept header is selected by this.configuration.selectHeaderAccept(httpHeaderAccepts) instead of both :

        if (httpHeaderAcceptSelected === undefined) {
            // to determine the Accept header
            const httpHeaderAccepts: string[] = [
                'text/csv',
                'application/problem+json'
            ];
            httpHeaderAcceptSelected = this.configuration.selectHeaderAccept(httpHeaderAccepts);
        }
        if (httpHeaderAcceptSelected !== undefined) {
            headers = headers.set('Accept', httpHeaderAcceptSelected);
        }

Generate the provided OpenAPI example with the typescript-angular command, then inspect the generated request around configuration.selectHeaderAccept and its response parsing. Locate the corresponding generator template and verify that the generated client handles the declared text/csv success response and application/problem+json failure response without a JSON.parse error.