I would have preferred the as operator like as HttpQuery.

Or even cleaner would be extending the definition of HttpQuery:

type HttpQuery = { [key: string]: string | number | null | boolean | Array<string | number | null | boolean> } | {};

Then the generated controllers would not be affected at all.

@denyo will you file a PR to make the changeS?

I can't before next week.

with

type HttpQuery = { [key: string]: string | number | null | boolean | Array<string | number | null | boolean> } | {};

the type-safety is lost, i.e.

const bla: HttpQuery = { bla: new SomeObject()};

can be assigned without errors. See http://www.typescriptlang.org/play/index.html?ssl=13&ssc=47&pln=13&pc=1#code/C4TwDgpgBAEsxgIoFcICcRQLxQN5QG0BrCEALigGdg0BLAOwHMBdC6upqAHynuQFsARum69kAG3GjBAexniIAQ3qiAgmjSKQAHnYNGovkJE8+k6XIXKAfFAC+o3HYDcAWABQHgMYz61KGgQAI6o1AAKipr8EMDolNh4HlDJUMiU6PSK0RQA5DkANEkpYIqUlADuMmgAJrk5HnYe3r7+QRRwCCjomDhObu4+fsBQId3t8EioGAn4AHTzABSBo+GRWTFxs2kZ61AAZHt4UDnbaJnRORTLocARURtolFvpZ7t2AJT5UPOzS8E3d3WsUesxKZUqNX2h3wOTBFSq1UuAX+EFW92BTzhEOq9k+9n6g1aUxAACZxp1iQltB1Jt1rHNFtdUbc1tEMc8dtEoUcTi9zhAkUy0UDNqd+bivj8-isWejNliEdyYQqaoKUcK2fLSvDIR8vi4mu4APRGqgACxkEhx9BkwwhRGaQyggnEinJtOmvWdroo9Ag5SgADEqvwACKKYCKBbvA3uIA

The problem is this:

type HttpQuery = ... | {};

If HttpQuery is defined as such, it should work:

type HttpQuery = Partial<{ [key: string]: string | number | null | boolean | Array<string | number | null | boolean> }>;

See a working example: TS Playground

@macjohnny thanks for the PR, which has been included in v4.2.0 release: https://twitter.com/oas_generator/status/1189824932345069569