How to do locale fallback lookup?

[faassen]

I think that when I ask, for instance, for a collator given a locale, and that specific locale does not exist, it cannot find a collator. Instead I'd like it to fall back on another locale if possible.

I also found this document:

https://docs.google.com/document/d/1Mp7EUyl-sFh_HZYgyeVwj88vJGpCBIWxzlCwGgLCDwM/edit#heading=h.3jl4998lrpbp

which seems to have inspired this code:

https://docs.rs/icu_provider_adapters/latest/icu_provider_adapters/fallback/index.html

I want to try using this, but I don't understand how to turn a BlobDataProvider into a LocalFallbackProvider, because it doesn't have a try_new_with_buffer_provider constructor.

Is this intentional? Is it that buffer providers don't provide enough information yet, and this is not yet in the CLDR, as hinted at here:

#2243

But maybe I'm on the wrong tack altogether. I can implement "subtag stripping" (as referenced by the google doc) manually but I was hoping there was something already.

So let's backtrack to the base question: how do I implement a locale fallback mechanism using icu4x?

[Manishearth]

The constructors you need are available with the serde feature enabled, looks like for this crate we do not have the all-features = true docs.rs key set for 1.2 (it's fixed in 1.3), but the functions exist. A local docs build should turn up the functions you need.

[sffc]

looks like for this crate we do not have the all-features = true docs.rs key set for 1.2 (it's fixed in 1.3)

oops!

[faassen]

Ah, thanks, I will add the feature!

[sffc]

I just hit merge on #3334 which adds a tutorial example for this.

[faassen]

The missing serde dependency was indeed the problem. Now I'm using a fallback provider, and an either provider too (as fallback can be turned on and off), and it all appears to work the way I expect! Thank you so much for the good work!