Do not emit an empty module export in the index if no module is required

[hristozov]

Problem

See #337

We might not want a module but still want an index, e.g.:

{
  "module": false,
  "indexFile": true
}

In such a case, we'd get something like:

/* tslint:disable */
/* eslint-disable */
/* Code generated by ng-openapi-gen DO NOT EDIT. */

export { ApiConfiguration } from './api-configuration';
export { BaseService } from './base-service';
export { RequestBuilder } from './request-builder';
export { StrictHttpResponse } from './strict-http-response';
export {  } from './';   // <----------------------------------------- Note this broken export
export { ApiService } from './services/api.service';

Solution

Guard the export in the template. Be sure to not break things by writing tests for the exports in index.ts for both cases - whenever module is on or off.

Testing done

Verified the output no longer contains such an export in that case.

Verified the existing exports are not regressed.

Compared the test output before and after the fix:

$ diff -r out-before out-after
diff --color -r out-before/all-operations/fn/no-tag/path-6-get.ts out-after/all-operations/fn/no-tag/path-6-get.ts
21c21
<     rb.build({ responseType: 'arraybuffer', accept: '*/*', context })
---
>     rb.build({ responseType: 'blob', accept: '*/*', context })
diff --color -r out-before/noModule/index.ts out-after/noModule/index.ts
9d8
< export {  } from './';

(The diff in path-6-get.ts seems unrelated, probably due to non-determinism)