oapi-codegen fails with openapi 3.0.2 and references to relative schemas containing $defs

[feliperoos]

Hi Folks,

I'm been looking into a case where we seem to have hit some wall. For some reason, Swagger UI is able to handle the case attached, but the oapi-codegen can't make sense of the included/referenced json schema file.

Made use of oapi-codegen 1.12.4.

openapi-3.0.2-ref-schema-defs.zip

[ryepup]

This might be the same as #867