OpenApi generation creates NullableOf version of structs when null is allowed?

[Markz878]

Not sure if this is a question, bug report or API proposal, but I was pretty surprised when I tried to switch from Swagger to .NET 9 OpenApi generation, and saw that it generates these NullableOfXXX versions of structs if the API has any endpoints where the struct is nullable in input or output objects. What is the purpose of them?

This makes it harder to migrate from Swagger api generation to this, because we have auto-generated the Typescript schema objects and this would need a lot of changes in the app's TS signatures.

I'm not an OpenApi expert, but couldn't this be handled by using oneOf or anyOf?
Or can this be somehow disabled using the OpenApi configuration? This doesn't happen with classes, why are structs handled differently?

[Atulin]

I'm having the same issue. Switching from Swagger generated a bunch of NullableOf, IEnumerableOf, DictionaryOf and other types of this kind, instead of having them inlined. The worst offender are probably enums and collections of primitives. I really don't need NullableOfMyEnum and IEnumerableOfInt64 when just { "$ref": "#/components/schemas/MyEnum", "nullable": true } would suffice.

[ClementCHA]

I'm also having the same issue. Fun part is that, if a model is using nullable Propriety AND an other model using the same propriety but non nullable this time, it will add it twice in the json as NullableOfProperty & Property