Outline of making optional paramters explicit as Union with None

[dctr]

Related discussion

Approaching the task of making optional parameters explicit by making the respective types a Union[..., None] to conform with existing coding conventions.

• Add None to Unions of existing types where possible
• Where parameters are classes or other Non-Union types, use Optional[T]
• Import needed types from typing directly to avoid noisy prefixing

This approach fails for RequestFiles in _content.py > encode_request(). The method does a None-check on the files parameter, from where onwards the value can not be None anymore. And _multipart.py > _iter_fields() requires an iterator on the type, which all types suffice, except for None of course.

As outlined in the linked discussion, using Optional[T] for optional types will solve this, as up until encode_request() the parameter could be Optional[RequestFiles] and just RequestFiles after the None-check.