Records and annotations
john.r.rose at oracle.com
Thu Jun 6 22:18:17 UTC 2019
On Jun 6, 2019, at 1:48 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
> But, I’m not particularly compelled by this — I think the strategy we took for enums is mostly good enough. So I’m voting for pure B.
Yes, I track with your reasoning. Pure B is perfectly
fine as wherever there is a mandated translation strategy
to inform the user where (in the reflective APIs) to look
for the annotation.
You can achieve A-like effects with appropriate conventions.
For example, if I have a little library of annotations just for
record components, I can target them to fields, and look for
them in Class.getDeclaredFields, even if the fields happen to
be private. (Right?) I'd kind of like to call this B+-. No new
channels or API points, but a known way to find component
annotations, by looking at the fields.
If we wanted to make things more explicit, we could incrementally
modify a plan B with A-like conventions to a plan B+ in which
there's a new annotation target for components, but it still gets
passed through the field channels. This wouldn't require new
API points or classfile formats. Strictly speaking a new annotation
target isn't required either, just some marker or other; another
meta-annotation, but not a target type.
The net of the above is B seems sufficient, although it also seems
necessary to specify a deterministic place to find component
annotations per se (fields, I suppose). And if we want to do
more it's easy to add a bit meta-data with a meta-annotation,
not necessarily a target type.
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