Bug: order of types in openapi spec is not consistent in json rendering

[atom-andrew]

Description

We are seeing the order of types change in openapi generation, which makes comparing golden versions of the openapi spec problematic. I think the specific problem we are seeing comes from

litestar/litestar/_openapi/schema_generation/schema.py

Line 160 in ffaf561

schema_types = list(set(schema_types))

where we use the set operation to uniquify the list of types. The order doesn't matter to the correctness of the openapi spec, so perhaps the responsibility for ensuring a determistic spec file could also come from the serializer, but either way it would be helpful if we could always render the same openapi spec the same way.

URL to code causing the issue

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MCVE

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Steps to reproduce

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Litestar Version

2.9.1

Platform

• Linux
• Mac
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[provinzkraut]

Having this be consistent makes sense to me. There are 2 ways to fix this: Either sort the items after they have been deduplicated, or remove the usage of a set entirely. Sorting is easier, but not using a set to begin with gives us the opportunity to preserve order, which, while not necessary, could be a bit nicer to work with.

@atom-andrew Since you've already figured out what the issue is, would you be interested in submitting a PR with a fix? :)

[atom-andrew]

@provinzkraut I'm happy to submit a PR but it wasn't obvious to me where this would be tested. Can you give me a tip about where it would make sense to include a test for this? Thanks.