Special case English translation fallback

We should not be listing this in LINGUAS as that gives the impression
that English has en explicit translation. Instead, it is a special case
that the code needs to be explicitly aware of.

This reverts 9a06058 in favour of a more robust fix.

app/localization.js

@@ -40,12 +40,6 @@ export class Localizer {
                 .replace("_", "-")
                 .split("-");
 
-            // Built-in default?
-            if ((userLang[0] === 'en') &&
-                ((userLang[1] === undefined) || (userLang[1] === 'us'))) {
-                return;
-            }
-
             // First pass: perfect match
             for (let j = 0; j < supportedLanguages.length; j++) {
                 const supLang = supportedLanguages[j]
@@ -64,7 +58,12 @@ export class Localizer {
                 return;
             }
 
-            // Second pass: fallback
+            // Second pass: English fallback
+            if (userLang[0] === 'en') {
+                return;
+            }
+
+            // Third pass pass: other fallback
             for (let j = 0;j < supportedLanguages.length;j++) {
                 const supLang = supportedLanguages[j]
                     .toLowerCase()

app/ui.js

@@ -1762,7 +1762,7 @@ const UI = {
 };
 
 // Set up translations
-const LINGUAS = ["cs", "de", "el", "en", "es", "fr", "it", "ja", "ko", "nl", "pl", "pt_BR", "ru", "sv", "tr", "zh_CN", "zh_TW"];
+const LINGUAS = ["cs", "de", "el", "es", "fr", "it", "ja", "ko", "nl", "pl", "pt_BR", "ru", "sv", "tr", "zh_CN", "zh_TW"];
 l10n.setup(LINGUAS);
 if (l10n.language === "en" || l10n.dictionary !== undefined) {
     UI.prime();

tests/test.localization.js

@@ -27,6 +27,16 @@ describe('Localization', function () {
             l10n.setup(["es", "fr"]);
             expect(l10n.language).to.equal('en');
         });
+        it('should fall back to generic English for other English', function () {
+            window.navigator.languages = ["en-AU", "de"];
+            l10n.setup(["de", "fr", "en-GB"]);
+            expect(l10n.language).to.equal('en');
+        });
+        it('should prefer specific English over generic', function () {
+            window.navigator.languages = ["en-GB", "de"];
+            l10n.setup(["de", "en-AU", "en-GB"]);
+            expect(l10n.language).to.equal('en-GB');
+        });
         it('should use the most preferred user language', function () {
             window.navigator.languages = ["nl", "de", "fr"];
             l10n.setup(["es", "fr", "de"]);