Spec transformation to stay backward-compatible

[jmini]

This is more a question or a feature request than a real issue.

We would like to try following approach:

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Given two specifications (old.yaml and new.yaml) representing two versions (v1 and v2) of an API. They are similar (say 90% for example) but there are braking changes between the two specs.

There could be a way to compute a second version of old.yaml (say old2.yaml) containing only the backward-compatible changes that are requested in order to transform old.yaml into new.yaml.

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Is this something that someone has already investigated?
I think that the diff computed by openapi-diff tool is a good basis to realise a tool like this.
Is someone else interested?

Thank you in advance for your feedback.

Do not hesitate to tell, if I am not clear enough about what I mean.

[quen2404]

Yes it's a good idea. A tool which automate the generation of a backward compatible contract could be useful.

[jmini]

Thank you for your feedback.

Maybe a first step is to have the possibility to apply a diff result on a specification.
Take spec1 and spec2: with the ChangedOpenApi object obtained with OpenApiCompare.fromSpecifications(spec1, spec2), when its content is applied to spec1, I should obtain spec2.

[itsjavi]

Hi, first thanks for this amazing tool <3
I am planning to have a CI step/job in one of my projects to check for backwards incompatible changes between an old spec and new one.
Reading the documentation I am a bit confused about how to do that without parsing the output result message.

I am not interested in the output in that particular step, I only want openapi-diff to exit with 0 if there are no breaking changes or with an error if there was breaking changes.

What would be the proper command for that? @quen2404

[jmini]

I would appreciate if you were using an other issue to ask a question, because this has nothing to do with this issue. I will be happy to discuss it with you and to help you.

[itsjavi]

@jmini yeah sorry. I opened an issue for that.

[DrSatyr]

As for my understanding, this is a good idea for another tool built on top of openapi-diff. let's say openapi-merge. It can rely on compatibility detection from openapi-diff and decide whether changes need to be merged or not.