feat(os): add `locale` API

Ref https://github.com/tauri-apps/tauri/pull/5960

Cargo.lock

@@ -4895,6 +4895,16 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "sys-locale"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea0b9eefabb91675082b41eb94c3ecd91af7656caee3fb4961a07c0ec8c7ca6f"
+dependencies = [
+ "libc",
+ "windows-sys 0.45.0",
+]
+
 [[package]]
 name = "system-deps"
 version = "6.0.4"
@@ -5271,6 +5281,7 @@ dependencies = [
  "os_info",
  "serde",
  "serde_json",
+ "sys-locale",
  "tauri",
  "thiserror",
 ]

plugins/os/Cargo.toml

@@ -12,3 +12,4 @@ tauri = { workspace = true }
 log = { workspace = true }
 thiserror = { workspace = true }
 os_info = "3"
+sys-locale = "0.3"

plugins/os/guest-js/index.ts

@@ -123,5 +123,22 @@ async function tempdir(): Promise<string> {
   return invoke("plugin:os|tempdir");
 }
 
-export { EOL, platform, version, type, arch, tempdir };
+/**
+ * Returns a String with a `BCP-47` language tag inside. If the locale couldn’t be obtained, `null` is returned instead.
+ * @example
+ * ```typescript
+ * import { locale } from '@tauri-apps/plugin-os';
+ * const locale = await locale();
+ * if (locale) {
+ *    // use the locale string here
+ * }
+ * ```
+ *
+ * @since 1.3.0
+ */
+async function locale(): Promise<string | null> {
+  return invoke("plugin:os|locale");
+}
+
+export { EOL, platform, version, type, arch, tempdir, locale };
 export type { Platform, OsType, Arch };

plugins/os/src/commands.rs

@@ -28,3 +28,8 @@ pub fn arch() -> &'static str {
 pub fn tempdir() -> PathBuf {
     crate::tempdir()
 }
+
+#[tauri::command]
+pub fn locale() -> Option<String> {
+    crate::locale()
+}

plugins/os/src/lib.rs

@@ -68,6 +68,11 @@ pub fn tempdir() -> PathBuf {
     std::env::temp_dir()
 }
 
+/// Returns the locale with the `BCP-47` language tag. If the locale couldn’t be obtained, `None` is returned instead.
+pub fn locale() -> Option<String> {
+    sys_locale::get_locale()
+}
+
 pub fn init<R: Runtime>() -> TauriPlugin<R> {
     Builder::new("os")
         .invoke_handler(tauri::generate_handler![
@@ -75,7 +80,8 @@ pub fn init<R: Runtime>() -> TauriPlugin<R> {
             commands::version,
             commands::kind,
             commands::arch,
-            commands::tempdir
+            commands::tempdir,
+            commands::locale
         ])
         .build()
 }