How to serde Locale?

[xuxiaocheng0201]

Cargo.toml:

[dependencies]
serde = { version = "^1.0", features = ["derive"] }
icu_locale = { version = "^2.0", features = ["serde"] }

lib.rs:

#[derive(serde::Serialize, serde::Deserialize)]
struct Language {
    locale: icu_locale::Locale,
}

Run cargo build and report errores:

error[E0277]: the trait bound `Locale: Serialize` is not satisfied
    --> src/lib.rs:1:10
     |
1    | #[derive(serde::Serialize, serde::Deserialize)]
     |          ^^^^^^^^^^^^^^^^ the trait `Serialize` is not implemented for `Locale`
2    | struct Language {
3    |     locale: icu_locale::Locale,
     |     ------ required by a bound introduced by this call
     |
     = note: for local types consider adding `#[derive(serde::Serialize)]` to your `Locale` type
     = note: for types from other crates check whether the crate offers a `serde` feature flag
...
error[E0277]: the trait bound `Locale: Deserialize<'_>` is not satisfied
    --> src/lib.rs:3:13
     |
3    |     locale: icu_locale::Locale,
     |             ^^^^^^^^^^^^^^^^^^ the trait `Deserialize<'_>` is not implemented for `Locale`
     |
     = note: for local types consider adding `#[derive(serde::Deserialize)]` to your `Locale` type
     = note: for types from other crates check whether the crate offers a `serde` feature flag
...
error[E0277]: the trait bound `Locale: Deserialize<'_>` is not satisfied
  --> src/main.rs:1:28
   |
1  | #[derive(serde::Serialize, serde::Deserialize)]
   |                            ^^^^^^^^^^^^^^^^^^ the trait `Deserialize<'_>` is not implemented for `Locale`
   |
   = note: for local types consider adding `#[derive(serde::Deserialize)]` to your `Locale` type
   = note: for types from other crates check whether the crate offers a `serde` feature flag

[sffc]

You can serialize them as strings. The following docs page suggests an architecture that you can use for locale serialization to maximize efficiency:

https://unicode-org.github.io/icu4x/rustdoc/icu/locale/zerovec/index.html

[xuxiaocheng0201]

Alright, I will use LanguageIdentifier and ignore Extensions as a temporary solution.
I think this issue will be fixed soon, right? Thank you very much.

[sffc]

The LanguageIdentifier impl is very old: #89

It's unclear why a Locale impl wasn't included at the same time.

[sffc]

@sffc is there a reason we do not support non zerocopy ser/de for these types? Most users don't care about zerocopy when it comes to serialization.

I was posting an answer to the question, and the answer to the question is that we currently implement serializing Locale as a string only. I agree that we should revisit this in the TC in another issue.

[sffc]

Follow-up issue: #6824

If you'd like to make a PR @xuxiaocheng0201, you're welcome to do so. :)