Support OpenAPI 3.1.0

[ysndr]

OpenAPI version 3.1.0 came with some breaking changes, notably, the introduction of a null type and removal of the nullable attribute.

We can work around this by patching these parts of a 3.1.0 spec to a 3.0.* spec, but i'm concerned about the implication that has on the validity of the document.

Is an extension of progenitor to support OpenAPI 3.1.0 being considered or worked on?

[ahl]

Is an extension of progenitor to support OpenAPI 3.1.0 being considered or worked on?

Definitely considered. It's been low priority for us because of the generally slow uptake of 3.1. 3.1 also turns out to contain some extremely complicated features to support in particular with the adoption of JSON Schema 2020-12 and the jsonSchemaDialect property that allows random other schemas to be used instead. In addition the openapiv3 crate doesn't support 3.1--in part because the schemars crate doesn't support 2020-12.

In short: there's an expedient, but imprecise path forward that I've been deferring in the hope of doing the more complete things. Happy to discuss further if that would be helpful.

[ahl]

And I forgot: one important change in 2020-12 is how tuples are represented. Previously it was an array with items and additionalItems. In 2020-12 it became prefixItems and items where items is now always a singleton. It's a change for the better, but is also--obviously--incompatible.