Intl.NumberFormat’s formatToParts not implemented for iOS

[hector-del-rio]

Problem

Intl.NumberFormat.prototype.formatToParts works on Android but is not implemented for iOS.

Previously mentioned here.

Filing this as a separate issue as requested.

[dwxw]

This is a blocker for us adopting Hermes too.

[mattbfb]

I believe this is currently unavailable for iOS, and will be tacked as a part of a move to ICU (#1172)

[darshan09200]

We recently updated from 0.72.14 to 0.74.1 and started facing an issue where formatToParts is missing on iOS. We have added intl-numberformat polyfill to temporarily fix this.

Is there any official solution to resolve this issue?

[neildhar]

Our current Intl implementation uses APIs provided by the iOS or Android platform, but unfortunately, Intl often requires things that cannot be mapped onto the platform APIs. formatToParts is one such case, as we could not find a practical way to implement it on iOS.

We did previously expose a formatToParts method, but it had severe problems and we removed it last year. We did not take removing it lightly, but it seemed clear that Hermes users could not rely on it to serve them across locales.

We have a long term plan to fix this, and you can read about that in #1211.