Incorrect handling of marshmallow nested schema with allow_none=True in OpenAPI 3.1 about apispec

[jc-harrison]

Would you like to investigate this and propose a fix?

I'm not sure how soon I'll have time to investigate this further, I'm afraid, but I'll try to look into it at some point.

[lafrech]

I'm afraid you're right. Looks like a bug.

Would you like to investigate this and propose a fix?

[Bangertm]

@lafrech the problem here seems to be that field2nullable and nested2properties are operating independently. It looks like for OpenAPI 3.1 they are going to need to interoperate.

For this schema under 3.1 field2nullable is adding "type": ["null"] and nested2properties is independently adding "allOf": [{"$ref": "#/components/schemas/Foo"}]

This approach was probably fine pre 3.1, but now that nullability needs to be included in an anyOf array we need make one method depend on the result of the other.

This is probably also an issue for pluck2properties, but there the symptom would be not displaying nullability because the type is always being overwritten.

The solution I'm thinking about is:

1. Moving the execution of field2nullable to be the last attribute function executed. I think this change alone solves the Pluck case and the case of nested schemas defined inline.
2. Adding logic under the 3.1 case to translate the allOf keyword to anyOf while adding the null type.
3. We may also want to ensure that field2nullable executes after user defined attribute functions to prevent similar issues with those.

[sloria]

fix released in 6.6.1