feat: introduce navigator.language (#12322)

Link to the spec:
https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-language-dev

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

7 files changed, 62 insertions, 0 deletions

diff --git a/cli/dts/lib.deno.window.d.ts b/cli/dts/lib.deno.window.d.ts
index 77204fcbd..4ce288a4d 100644
--- a/cli/dts/lib.deno.window.d.ts
+++ b/cli/dts/lib.deno.window.d.ts
@@ -97,6 +97,8 @@ declare class Navigator {
   readonly gpu: GPU;
   readonly hardwareConcurrency: number;
   readonly userAgent: string;
+  readonly language: string;
+  readonly languages: string[];
 }
 
 /** @category Web APIs */
diff --git a/cli/dts/lib.deno.worker.d.ts b/cli/dts/lib.deno.worker.d.ts
index 10a771807..d274d4c05 100644
--- a/cli/dts/lib.deno.worker.d.ts
+++ b/cli/dts/lib.deno.worker.d.ts
@@ -61,6 +61,8 @@ declare class WorkerNavigator {
   readonly gpu: GPU;
   readonly hardwareConcurrency: number;
   readonly userAgent: string;
+  readonly language: string;
+  readonly languages: string[];
 }
 
 /** @category Web APIs */
diff --git a/cli/standalone.rs b/cli/standalone.rs
index 0c454ce77..528c55f1c 100644
--- a/cli/standalone.rs
+++ b/cli/standalone.rs
@@ -276,6 +276,7 @@ pub async fn run(
         .unwrap_or(1),
       debug_flag: metadata.log_level.map_or(false, |l| l == Level::Debug),
       enable_testing_features: false,
+      locale: deno_core::v8::icu::get_language_tag(),
       location: metadata.location,
       no_color: !colors::use_color(),
       is_tty: colors::is_tty(),
diff --git a/cli/tests/integration/run_tests.rs b/cli/tests/integration/run_tests.rs
index 004acb469..156940185 100644
--- a/cli/tests/integration/run_tests.rs
+++ b/cli/tests/integration/run_tests.rs
@@ -2377,6 +2377,59 @@ itest!(eval_context_throw_dom_exception {
   output: "run/eval_context_throw_dom_exception.js.out",
 });
 
+#[test]
+#[cfg(unix)]
+fn navigator_language_unix() {
+  let (res, _) = util::run_and_collect_output(
+    true,
+    "run navigator_language.ts",
+    None,
+    Some(vec![("LC_ALL".to_owned(), "pl_PL".to_owned())]),
+    false,
+  );
+  assert_eq!(res, "pl-PL\n")
+}
+
+#[test]
+fn navigator_language() {
+  let (res, _) = util::run_and_collect_output(
+    true,
+    "run navigator_language.ts",
+    None,
+    None,
+    false,
+  );
+  assert!(!res.is_empty())
+}
+
+#[test]
+#[cfg(unix)]
+fn navigator_languages_unix() {
+  let (res, _) = util::run_and_collect_output(
+    true,
+    "run navigator_languages.ts",
+    None,
+    Some(vec![
+      ("LC_ALL".to_owned(), "pl_PL".to_owned()),
+      ("NO_COLOR".to_owned(), "1".to_owned()),
+    ]),
+    false,
+  );
+  assert_eq!(res, "[ \"pl-PL\" ]\n")
+}
+
+#[test]
+fn navigator_languages() {
+  let (res, _) = util::run_and_collect_output(
+    true,
+    "run navigator_languages.ts",
+    None,
+    None,
+    false,
+  );
+  assert!(!res.is_empty())
+}
+
 /// Regression test for https://github.com/denoland/deno/issues/12740.
 #[test]
 fn issue12740() {
diff --git a/cli/tests/testdata/navigator_language.ts b/cli/tests/testdata/navigator_language.ts
new file mode 100644
index 000000000..1cdbc2fe6
--- /dev/null
+++ b/cli/tests/testdata/navigator_language.ts
@@ -0,0 +1 @@
+console.log(navigator.language);
diff --git a/cli/tests/testdata/navigator_languages.ts b/cli/tests/testdata/navigator_languages.ts
new file mode 100644
index 000000000..41dece950
--- /dev/null
+++ b/cli/tests/testdata/navigator_languages.ts
@@ -0,0 +1 @@
+console.log(navigator.languages);
diff --git a/cli/worker.rs b/cli/worker.rs
index 581d4f90f..10fe5b36f 100644
--- a/cli/worker.rs
+++ b/cli/worker.rs
@@ -418,6 +418,7 @@ pub async fn create_main_worker(
         .log_level()
         .map_or(false, |l| l == log::Level::Debug),
       enable_testing_features: ps.options.enable_testing_features(),
+      locale: deno_core::v8::icu::get_language_tag(),
       location: ps.options.location_flag().map(ToOwned::to_owned),
       no_color: !colors::use_color(),
       is_tty: colors::is_tty(),
@@ -534,6 +535,7 @@ fn create_web_worker_callback(
           .log_level()
           .map_or(false, |l| l == log::Level::Debug),
         enable_testing_features: ps.options.enable_testing_features(),
+        locale: deno_core::v8::icu::get_language_tag(),
         location: Some(args.main_module.clone()),
         no_color: !colors::use_color(),
         is_tty: colors::is_tty(),