Redo of backport of JDK-8225377 (type annotations are not visible to javac plugins across compilation boundaries)

[Liam Miller-Cushon]

I wrote up a CSR for the proposed redo of the backport:
https://bugs.openjdk.org/browse/JDK-8346471

There are drafts of the PRs for the individual changes here:

https://github.com/openjdk/jdk21u-dev/pull/1037
https://github.com/openjdk/jdk21u-dev/pull/1251
https://github.com/openjdk/jdk21u-dev/pull/1252
https://github.com/openjdk/jdk21u-dev/pull/1253

On Thu, Aug 1, 2024 at 9:31 AM Werner Dietl <wdietl at gmail.com> wrote:

> I would also be very happy if this were backported to earlier JDKs.
> The pluggable type system frameworks I work on mostly have work-arounds
> for this issue, but it would be much nicer to have correct type-use
> annotation information from javac directly.
> I also agree with Chris's comment on having a positive feedback loop. Any
> positive change has some danger of breaking existing code. This shouldn't
> stop us from fixing bugs, improving the type-use annotation infrastructure,
> and enabling more adoption.
>
> Best,
> cu, WMD.
>
> On Mon, Jul 29, 2024 at 11:22 AM Chris Povirk <cpovirk at google.com> wrote:
>
>> Manu spoke about the ability to annotate different positions (e.g.,
>> type-parameter bounds) for improved nullness checking. I'd also call out
>> that this affects even users who use nullness annotations on "basic"
>> locations like fields, parameters, and return types: Unless tools use
>> internal javac APIs, type-use annotations in even these basic locations in
>> class files are invisible until JDK 22. (And as Josiah points out, this
>> affects more tools than just "nullness checkers." We've also seen it with
>> AutoValue
>> <https://github.com/google/auto/blob/main/value/userguide/index.md>.)
>> This means that type-use annotations are worse than declaration annotations
>> in some ways, even as they're better in others. As a result, users can't
>> confidently pick even a set of nullness annotations without evaluating the
>> tradeoffs. It would be great to be able to tell users "Use type-use
>> annotations" without waiting for them all to update to JDK 22.
>>
>> Plus: Even if the fix is backported today, experience shows that users
>> will also have to wait for some annotation processors to be enhanced to
>> start looking for type-use annotations _at all_. I'd be happy to see us
>> continue to drive that positive feedback loop: As type-use annotations
>> become more visible to annotation processors, tools increasingly get
>> modified to recognize them, leading to more adoption of type-use
>> annotations and more opportunity to identify and iron out remaining
>> wrinkles.
>>
>> Thanks,
>> Chris
>>
>
>
> --
> https://ece.uwaterloo.ca/~wdietl/
>
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