RFR: JDK-8310061: Note if implicit annotation processing is being used

[Joe Darcy]

On Thu, 15 Jun 2023 18:16:57 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> Emit a note warning of the possibility of changing the implicit running of annotation processors in a future release.

The goal of the change in this PR is to emit a message to users who may be unknowingly relying on default implicit annotation processing that the long-standing default may be changing in a future release. The message is a Note rather than a Warning to avoid running afoul of build setups using configurations like "-Xlint:all -Werror".

Semantically, the note about implicit processors is treated as on by default. The note is *not* emitted if there are explicit configuration options related to annotation processing, including the new-in-JDK-21 "-proc:full". and not emitted if the "options" lint check is explicitly disabled, either through "-Xlint:-options" or "-Xlint:none".

A targeted regression test for the change to follow.

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PR Comment: https://git.openjdk.org/jdk/pull/14499#issuecomment-1595135616