Actual behavior (the bug)
I have a javalin server that has an API and an openapi specification, but no javalin-openapi annotations. (We actually use spec-first and generate the code with openapi-generator.tech which has a javalin6 generator as part of kotlin-server).

I serve the generated openapi.yaml under /openapi and register config.registerPlugin(SwaggerPlugin())

The swagger UI doesn't load under /swagger and says no API found.

Expected behavior
Swagger UI working under /swagger

To Reproduce
Set up project with just swagger plugin and a server openapi file.

Additional context
I found a workaround. The problematic code is

where OpenApiLoader is asked to provide all API versions.
I added a resource file openapi-plugin/.index with just the word default in it and then everything works.
It would be nice if the SwaggerPlugin config could accept the versions of the API (and maybe revert back to default if the openapi plugin is not active) so that this works more easily.