RFR: JDK-8267936: PreserveAllAnnotations option doesn't expose the annotation to Java code

[Peter Levart]

On Mon, 31 May 2021 12:37:55 GMT, David Holmes <david.holmes at oracle.com> wrote:

> That reads backwards to me. +PreserveAllAnnotations means that CLASS
> retention annotations are retained by the VM not just RUNTIME ones. So
> in that sense it might be a migration aid if moving from RUNTIME to
> CLASS, not CLASS to RUNTIME.
> 
> David

Ah, I know why you think that way. You think that when an annotation is migrated from RUNTIME to CLASS retention, that some users would still want to "see" it via reflection (at runtime)...

No, I don't think this was the intention of the JVM option. Migrating from RUNTIME to CLASS retention means that the ways of looking up such annotation are shrinking. Such change to the annotation should only be attempted when there are no more runtime lookups to support. So 1st deprecation of RUNTIME retention on the annotation should be published, followed by change to CLASS retention.

OTOH when CLASS retention is changing to RUNTIME, such as in this case, the ways of looking up are widening (there is some new desire to lookup the annotation at runtime via reflection). To facilitate that, the annotation maintainer changes the retention to RUNTIME. But unfortunately, old uses of the annotation are baked in the ` RuntimeInvisibleAnnotations` attributes of the classes that were compiled with the old version of the annotation when the retention was still CLASS. Until all such classes are recompiled, the JVM option can be used to make such annotation usages visible at runtime. That makes more sense to me.

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PR: https://git.openjdk.java.net/jdk/pull/4245