feat: Add v8::icu::get_language_tag() (#953)

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>
Co-authored-by: Bert Belder <bertbelder@gmail.com>

src/binding.cc

@@ -4,6 +4,7 @@
 #include <iostream>
 
 #include "support.h"
+#include "unicode/locid.h"
 #include "v8-callbacks.h"
 #include "v8/include/libplatform/libplatform.h"
 #include "v8/include/v8-fast-api-calls.h"
@@ -3148,3 +3149,24 @@ void v8__CompiledWasmModule__DELETE(v8::CompiledWasmModule* self) {
   delete self;
 }
 }  // extern "C"
+
+// icu
+
+extern "C" {
+
+size_t icu_get_default_locale(char* output, size_t output_len) {
+  const icu_71::Locale& default_locale = icu::Locale::getDefault();
+  icu_71::CheckedArrayByteSink sink(output, static_cast<uint32_t>(output_len));
+  UErrorCode status = U_ZERO_ERROR;
+  default_locale.toLanguageTag(sink, status);
+  assert(status == U_ZERO_ERROR);
+  assert(!sink.Overflowed());
+  return sink.NumberOfBytesAppended();
+}
+
+void icu_set_default_locale(const char* locale) {
+  UErrorCode status = U_ZERO_ERROR;
+  icu::Locale::setDefault(icu::Locale(locale), status);
+}
+
+}  // extern "C"

src/icu.rs

@@ -1,4 +1,8 @@
+use std::{ffi::CString, os::raw::c_char};
+
 extern "C" {
+  fn icu_get_default_locale(output: *mut c_char, output_len: usize) -> usize;
+  fn icu_set_default_locale(locale: *const c_char);
   fn udata_setCommonData_71(this: *const u8, error_code: *mut i32);
 }
 
@@ -47,3 +51,19 @@ pub fn set_common_data_71(data: &'static [u8]) -> Result<(), i32> {
     Err(error_code)
   }
 }
+
+/// Returns BCP47 language tag.
+pub fn get_language_tag() -> String {
+  let mut output = [0u8; 1024];
+  let len = unsafe {
+    icu_get_default_locale(output.as_mut_ptr() as *mut c_char, output.len())
+  };
+  std::str::from_utf8(&output[..len]).unwrap().to_owned()
+}
+
+pub fn set_default_locale(locale: &str) {
+  unsafe {
+    let c_str = CString::new(locale).expect("Invalid locale");
+    icu_set_default_locale(c_str.as_ptr());
+  }
+}

tests/test_api.rs

@@ -6764,6 +6764,13 @@ fn instance_of() {
   assert!(array.instance_of(&mut scope, array_constructor).unwrap());
 }
 
+#[test]
+fn get_default_locale() {
+  v8::icu::set_default_locale("nb_NO");
+  let default_locale = v8::icu::get_language_tag();
+  assert_eq!(default_locale, "nb-NO");
+}
+
 #[test]
 fn weak_handle() {
   let _setup_guard = setup();