[PP-1] Core Date field is serialized as String instead of timestamp/long

This is blocked on #2926508: Add DateTimeNormalizer+TimestampNormalizer, deprecate TimestampItemNormalizer: @DataType-level normalizers are reusable by JSON:API. Once that is fixed, this should be fixed too. The scope of this issue will then be to provide tests, to ensure BC.

Thanks for creating that core issue @Wim Leers. A workaround for the time being is to use JSON API Extras with the date field enhancers.

#2926508: Add DateTimeNormalizer+TimestampNormalizer, deprecate TimestampItemNormalizer: @DataType-level normalizers are reusable by JSON:API now has a patch that should mostly work. See #2926508-4: Add DateTimeNormalizer+TimestampNormalizer, deprecate TimestampItemNormalizer: @DataType-level normalizers are reusable by JSON:API + #2926508-5: Add DateTimeNormalizer+TimestampNormalizer, deprecate TimestampItemNormalizer: @DataType-level normalizers are reusable by JSON:API.

TimestampItem fields in JSON API should then in theory get the same normalization as in core. Will need tests of course. And we'll first need to see whether we can get this to land in core at all.

Oh wait, this is about DateTimeItem, not TimestampItem?

LOL, I had the same mixup in the jsonapi_extras issue queue @Wim Leers.

Hm, it looks/sounds like you created a date field (DateTimeItem) that is configured to store only a date (\Drupal\datetime\Plugin\Field\FieldType\DateTimeItem::DATETIME_TYPE_DATE).

Then #2870609: [PP-1] Core Date field is serialized as String instead of timestamp/long is the relevant issue.

FFS copy/paste is fragile. The links in #7 obviously didn't make sense.

We're fixing this in #2929932: Work around core's ill-designed @FieldType-level TimestampItemNormalizer normalization until #2926508 lands for timestamp fields. But it should also handle datetime and daterange fields, see #2929932-5: Work around core's ill-designed @FieldType-level TimestampItemNormalizer normalization until #2926508 lands.

#2929932: Work around core's ill-designed @FieldType-level TimestampItemNormalizer normalization until #2926508 lands is now green and RTBC! Closing this as a duplicate now :)