[icu-design] ICU API proposal: change the value of UIDNA_DEFAULT to nontransitional processing

Dear ICU team & users,

I would like to propose the following API for: ICU 76
Please provide feedback by: next Wednesday, 2024-09-11
Designated API reviewer: Mark

Ticket: ICU-22294 “UTS #46: mark transitional processing as deprecated, maybe change DEFAULT value”

After all major browsers have switched to nontransitional processing, Unicode 15.1 (a year ago) changed the UTS #46 spec to declare transitional processing deprecated.

I propose that we change the "DEFAULT" API constants from 0 to UIDNA_NONTRANSITIONAL_TO_ASCII | UIDNA_NONTRANSITIONAL_TO_UNICODE.

I will not change the behavior of using options value 0. That would change the behavior of existing binaries linking with new ICU libraries. However, when code is recompiled against a new version of ICU, and when it uses the DEFAULT constant, then it will pass these option flags into the factory method.

In C/C++: unicode/uidna.h UIDNA_DEFAULT

In Java: IDNA.java DEFAULT

This also involves some documentation changes, of course.

Sincerely,

markus