Figure out why optional function arguments become query parameters instead of body payload in ninja openapi schema

[tykling]

thumbnail_data and thumbnail_metadata in the /files/upload/ api endpoint are optional and default to None. The type annotation should be UploadedFile | None but including None makes thumbnail_data and thumbnail_metadata become parameters instead of body payload in the openapi schema.

The workaround of not including None in the annotation shows thumbnail_data and thumbnail_metadata as part of request body as expected, but the annotation is wrong:

    thumbnail_data: File[UploadedFile] = None,
    thumbnail_metadata: Body[ImageMetadataSchema] = None,

Shows thumbnail_data and thumbnail_metadata as part of query parameters, but the annotation is correct:

    thumbnail_data: File[UploadedFile] | None = None,
    thumbnail_metadata: Body[ImageMetadataSchema] | None = None,

The buggy code is in https://github.com/vitalik/django-ninja/blob/be55f63368d6ece4701c356ebec890476691e7fd/ninja/signature/details.py#L218 so create a minimal reproducer and open a ninja issue

[tykling]

Workaround makes mypy mad ofc:

src/files/api.py:75: error: Incompatible default for argument "thumbnail_data" (default has type "None", argument has type "UploadedFile")  [assignment]
src/files/api.py:75: note: PEP 484 prohibits implicit Optional. Accordingly, mypy has changed its default to no_implicit_optional=True
src/files/api.py:75: note: Use https://github.com/hauntsaninja/no_implicit_optional to automatically upgrade your codebase
src/files/api.py:76: error: Incompatible default for argument "thumbnail_metadata" (default has type "None", argument has type "ImageMetadataSchema")  [assignment]
src/files/api.py:76: note: PEP 484 prohibits implicit Optional. Accordingly, mypy has changed its default to no_implicit_optional=True
src/files/api.py:76: note: Use https://github.com/hauntsaninja/no_implicit_optional to automatically upgrade your codebase
Found 2 errors in 1 file (checked 141 source files)