Typescript-fetch: Invalid import of isomorphic-fetch causing TypeError

Description

Hello, I've encountered an issue with generated code for typescript-fetch. The generated api.ts file contains import of portable-fetch which isn't correct:

import * as portableFetch from "portable-fetch";

When fixed to

import portableFetch from "portable-fetch";

the code works as expected.

Swagger-codegen version

2.4.12

Command line used for generation

swagger-codegen generate -i swagger.yaml -l typescript-fetch -o src/shared/apiClient/

Steps to reproduce

1. Generate code with codegen for typescript-fetch.
2. Try to use API using the generated code.

You'll always get:

TypeError: fetch is not a function

Suggest a fix/enhancement

I've found this code is generated from moustache template here. I can create pull request and fix it, however, I'm not sure if I'm missing something and the code should work under other circumstances as it's there for very long time without a fix. Please advise, thanks!

Start with modules/swagger-codegen/src/main/resources/typescript-fetch/api.mustache and inspect the generated api.ts import. Reproduce the issue with the provided swagger-codegen command, then verify that generated typescript-fetch code can call the API without the reported “fetch is not a function” TypeError.