Don't request locales we don't have; use fallback locales

build.js

@@ -123,5 +123,6 @@ fs.writeFileSync('data/data.js', 'iD.data = ' + stringify({
     },
     imperial: r('imperial.json'),
     maki: r('maki-sprite.json'),
+    locales: r('locales.json'),
     en: read('dist/locales/en.json')
 }) + ';');

data/data_dev.js

@@ -15,6 +15,7 @@ iD.data = {
             path + 'data/presets/fields.json',
             path + 'data/imperial.json',
             path + 'data/maki-sprite.json',
+            path + 'data/locales.json',
             path + 'dist/locales/en.json'
             ], d3.json, function (err, data) {
 
@@ -31,7 +32,8 @@ iD.data = {
                 },
                 imperial: data[8],
                 maki: data[9],
-                en: data[10]
+                locales: data[10],
+                en: data[11]
             };
 
             callback();

data/locales.json

@@ -0,0 +1,25 @@
+[
+    "af",
+    "bs",
+    "zh",
+    "zh_TW",
+    "cs",
+    "da",
+    "nl",
+    "fr",
+    "de",
+    "hu",
+    "it",
+    "ja",
+    "lv",
+    "pl",
+    "pt",
+    "ru",
+    "sr",
+    "sk",
+    "es",
+    "sv",
+    "tr",
+    "uk",
+    "vi"
+]

data/update_locales.js

@@ -56,6 +56,7 @@ function getResource(resource, callback) {
 
         });
 
+        fs.writeFileSync('data/locales.json', JSON.stringify(codes, null, 4));
     });
 }
 

js/id/id.js

@@ -38,7 +38,12 @@ window.iD = function () {
             context.container(container);
 
             var detectedLocale = iD.detect().locale;
-            if (detectedLocale !== 'en') {
+
+            if (iD.data.locales.indexOf(detectedLocale) === -1) {
+                detectedLocale = detectedLocale.split('-')[0];
+            }
+
+            if (detectedLocale !== 'en' && iD.data.locales.indexOf(detectedLocale) !== -1) {
                 d3.json(context.assetPath() + 'locales/' + detectedLocale + '.json', function(err, result) {
                     locale[detectedLocale] = result;
                     locale.current(detectedLocale);