Fix regional locale detection

2026-09-01 08:51:35 +02:00 · 2026-07-30 14:29:25 +05:30
parent 146c287aba
commit cb3f0b49a8
3 changed files with 124 additions and 6 deletions
@@ -0,0 +1,74 @@
+import { assertEquals } from "@test/assert";
+import { detectLocale } from "./detectLocale";
+
+function runTests() {
+    assertEquals(
+        detectLocale("zh-TW,zh;q=0.9,en-US;q=0.8,en;q=0.7,ja;q=0.6"),
+        "zh-TW",
+        "An exact regional match should take precedence over a language fallback"
+    );
+    assertEquals(
+        detectLocale("ZH-tw"),
+        "zh-TW",
+        "Locale matching should be case-insensitive"
+    );
+    assertEquals(
+        detectLocale("  zh-TW ; q=1 , zh-CN;q=0.8 "),
+        "zh-TW",
+        "Whitespace and quality parameters should not prevent an exact match"
+    );
+    assertEquals(
+        detectLocale("zh-CN,zh-TW;q=0.9"),
+        "zh-CN",
+        "Simplified Chinese should still match exactly"
+    );
+    assertEquals(
+        detectLocale("zh"),
+        "zh-CN",
+        "A generic Chinese preference should retain the existing fallback"
+    );
+    assertEquals(
+        detectLocale("en-GB,en;q=0.9"),
+        "en-US",
+        "An unsupported region should fall back to a supported locale for the language"
+    );
+    assertEquals(
+        detectLocale("ja-JP,zh-TW;q=0.9"),
+        "zh-TW",
+        "The next preference should be used when a language is unsupported"
+    );
+    assertEquals(
+        detectLocale("zh-CN;q=0.5,zh-TW;q=0.9"),
+        "zh-TW",
+        "Preferences should be evaluated by quality"
+    );
+    assertEquals(
+        detectLocale("zh-TW;q=0,fr-FR;q=0.8"),
+        "fr-FR",
+        "Locales with zero quality should be excluded"
+    );
+    assertEquals(
+        detectLocale("*,de-DE;q=0.8"),
+        "de-DE",
+        "A wildcard should not obscure a supported preference"
+    );
+    assertEquals(
+        detectLocale("ja-JP"),
+        undefined,
+        "An unsupported language should not match"
+    );
+    assertEquals(
+        detectLocale(""),
+        undefined,
+        "An empty Accept-Language header should not match"
+    );
+
+    console.log("All locale detection tests passed!");
+}
+
+try {
+    runTests();
+} catch (error) {
+    console.error("Locale detection test failed:", error);
+    process.exit(1);
+}