During annotation processing, check that property types declared in additional-spring-configuration-metadata.json can be loaded

[wilkinsona]

It would be nice if the annotation processor had caught the problem fixed by #24851. Perhaps it could check that the types can be loaded when merging in the additional metadata.

[dreis2211]

I guess it will always choke up on the following:

    {
      "name": "spring.flyway.error-handlers",
      "type": "org.flywaydb.core.api.errorhandler.ErrorHandler[]",
      "deprecation": {
        "level": "error",
        "reason": "Flyway pro edition only."
      }
    },

This particular property was deprecated in 2.1.0 I think, so one could argue that this could be removed (or don't we do that at all?). Alternatively, the potential check could only cover non-deprecated stuff. I wanted to get it out of my head, because I saw that one as well after fixing my issue ;-)

EDIT: Another idea I had was to only limit the type check to java.* as those types should be available.

[wilkinsona]

I had a feeling we might hit a few problems like that. I'm not sure how best to handle them. Both your ideas are worth exploring. Thanks for those. Another might be to provide support for an allowlist that can be configured with any types that are known to be good but aren't on the classpath. Annotation processors aren't particularly easy to configure, though.

[snicoll]

Checking for java.* would be better than nothing although doing it for only a sub-set of the available types feels a bit odd.