Use Jakarta's @Generated annotation if available

[netdpb]

After javax.annotation.Generated was deprecated in Java 9, AutoValue and other users of GeneratedAnnotations started using the new javax.annotation.processing.Generated replacement if it was available (source version > 8), falling back to the deprecated one otherwise:

if sourceVersion > 8: javax.annotation.processing.Generated
else if in classpath: javax.annotation.Generated

However, it doesn't look for the new EE replacement, which was repackaged jakarta.annotation.Generated. Some users want to switch to that annotation when compiling for Java 8.

We could change GeneratedAnnotations to use the following logic:

if sourceVersion > 8: javax.annotation.processing.Generated
else if in classpath: jakarta.annotation.Generated // new
else if in classpath: javax.annotation.Generated

Alternatively, or in addition, we could add a supported option to each of our processors that lets users specify which @Generated annotation they want the processor to emit, which would let users override that default logic in case they want to emit a different one.

[From a discussion with @suztomo.]

[ronshapiro]

sourceversion > 8 is likely to be true in almost all compilations by this point, right? Especially for people that care about Jakarta.

Perhaps switch the conditions:

if in classpath: jakarta.annotation.Generated // new
else if sourceVersion > 8: javax.annotation.processing.Generated
else if in classpath: javax.annotation.Generated

[netdpb]

sourceversion > 8 is likely to be true in almost all compilations by this point, right? Especially for people that care about Jakarta.

Unfortunately, that's not the case—which is why this whole thing came up. The Google Cloud libraries are still built with Java 8.