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Disable annotation processing in AOT compilation step
By default, the compiler attempts to discover annotation processors from the classpath. This can have side effect on code that is generated ahead of time.
Adding -proc:none in the Maven and Gradle integration could be on way of making sure these don't run.
See also https://github.com/spring-projects/spring-framework/issues/30824 which now annotates every generated class which should trigger a warning if AP is active and no processor claimed it (which is likely to happen).
We may not need to do anything for Gradle builds. Gradle should ignore annotation processors on the compile classpath and only use those declared in the aotAnnotationProcessor configuration. If a user's made such a declaration I think we should honour it as it's very unlikely that it has been done accidentally.
@snicoll Do you have a sample project available that produces the warning?
Nope, sorry. I had the warning in framework tests using TestCompiler as it used to detects annotation processors from the classpath. I suspect that maybe the warnings from the compiler in the Maven plugin may not be redirected to the logs? I've tried to reproduce with a vanilla app and the context indexer and that didn't work. But I can see now that's because it claims all annotations. I'll have to dig a bit more.
Regardless, the issue is not really about the warning, but about the fact that, if I am not mistaken, AP (at least with Maven) are invoked by the AOT compilation run and shouldn't.
Regardless, the issue is not really about the warning, but about the fact that, if I am not mistaken, AP (at least with Maven) are invoked by the AOT compilation run and shouldn't.
Are we 100% sure that annotation processors should not run during the AOT compilation phase? If I user has something like Lombok or a null checker, won't they need to run the annotation processor?
After some more discussion with @snicoll things have become a bit clearer. We're not looking to disable annotation processing of user code, rather we'd want to make a change to this part of ProcessAotMojo so that annotation processors are not invoked on generated code.
We don't have complete control over the code that's generated. It's possible that someone has written a custom code generation contribution that relies on annotation processing. If we made this change, it would break them so I wonder if we'd also need to add a way to reverse it.