Refactor datefield to use proper fallbacks for HTML5

src/Forms/DateField.php

@@ -266,8 +266,8 @@ protected function getInternalFormatter()
     public function getAttributes()
     {
         $attributes = parent::getAttributes();
-
-        $attributes['lang'] = i18n::convert_rfc1766($this->getLocale());
+        $lang = $this->getLocale();
+        $attributes['lang'] = i18n::convert_rfc1766($lang);
 
         if ($this->getHTML5()) {
             $attributes['min'] = $this->getMinDate();
@@ -284,6 +284,7 @@ public function getSchemaDataDefaults()
         $defaults = parent::getSchemaDataDefaults();
         return array_merge($defaults, [
             'lang' => i18n::convert_rfc1766($this->getLocale()),
+            'isoLang' => i18n::convert_rfc1766(DBDate::ISO_LOCALE),
             'data' => array_merge($defaults['data'], [
                 'html5' => $this->getHTML5(),
                 'min' => $this->getMinDate(),
@@ -445,10 +446,6 @@ public function validate($validator)
      */
     public function getLocale()
     {
-        // Use iso locale for html5
-        if ($this->getHTML5()) {
-            return DBDate::ISO_LOCALE;
-        }
         return $this->locale ?: i18n::get_locale();
     }
 

src/Forms/DatetimeField.php

@@ -94,7 +94,8 @@ public function getAttributes()
     {
         $attributes = parent::getAttributes();
 
-        $attributes['lang'] = i18n::convert_rfc1766($this->getLocale());
+        $lang = $this->getLocale();
+        $attributes['lang'] = i18n::convert_rfc1766($lang);
 
         if ($this->getHTML5()) {
             $attributes['min'] = $this->internalToFrontend($this->getMinDatetime());
@@ -114,6 +115,7 @@ public function getSchemaDataDefaults()
         $defaults = parent::getSchemaDataDefaults();
         return array_merge($defaults, [
             'lang' => i18n::convert_rfc1766($this->getLocale()),
+            'isoLang' => i18n::convert_rfc1766(DBDate::ISO_LOCALE),
             'data' => array_merge($defaults['data'], [
                 'html5' => $this->getHTML5(),
                 'min' => $this->internalToFrontend($this->getMinDatetime()),

src/View/Requirements.php

@@ -327,17 +327,18 @@ public static function include_in_response(HTTPResponse $response)
      * directory will contain a number of JavaScript files named by language: en_US.js, de_DE.js,
      * etc.
      *
-     * @param string $langDir  The JavaScript lang directory, relative to the site root, e.g.,
+     * @param string $langDir The JavaScript lang directory, relative to the site root, e.g.,
      *                         'framework/javascript/lang'
-     * @param bool   $return   Return all relative file paths rather than including them in
+     * @param bool $return Return all relative file paths rather than including them in
      *                         requirements
      * @param bool $langOnly @deprecated 4.1.0:5.0.0 as i18n.js should be included manually in your project
      *
+     * @param bool $convertRFC1766 converts file candidates to be RFC1766 compatible
      * @return array
      */
-    public static function add_i18n_javascript($langDir, $return = false, $langOnly = false)
+    public static function add_i18n_javascript($langDir, $return = false, $langOnly = false, $convertRFC1766 = false)
     {
-        return self::backend()->add_i18n_javascript($langDir, $return);
+        return self::backend()->add_i18n_javascript($langDir, $return, $convertRFC1766);
     }
 
     /**

src/View/Requirements_Backend.php

@@ -996,9 +996,10 @@ public function includeInResponse(HTTPResponse $response)
      * @param bool $return Return all relative file paths rather than including them in
      *                         requirements
      *
+     * @param bool $convertRFC1766 converts file candidates to be RFC1766 compatible
      * @return array|null All relative files if $return is true, or null otherwise
      */
-    public function add_i18n_javascript($langDir, $return = false)
+    public function add_i18n_javascript($langDir, $return = false, $convertRFC1766 = false)
     {
         $langDir = ModuleResourceLoader::singleton()->resolvePath($langDir);
 
@@ -1012,6 +1013,9 @@ public function add_i18n_javascript($langDir, $return = false)
             i18n::get_locale() . '.js',
         );
         foreach ($candidates as $candidate) {
+            if ($convertRFC1766) {
+                $candidate = i18n::convert_rfc1766($candidate);
+            }
             $relativePath = Path::join($langDir, $candidate);
             $absolutePath = Director::getAbsFile($relativePath);
             if (file_exists($absolutePath)) {

src/i18n/i18n.php

@@ -303,7 +303,7 @@ public static function get_closest_translation($locale)
      */
     public static function convert_rfc1766($locale)
     {
-        return str_replace('_', '-', $locale);
+        return strtolower(str_replace('_', '-', $locale));
     }
 
     /**

tests/php/Forms/FormSchemaTest/testSchemaValidation.json

@@ -68,7 +68,8 @@
                 "min": null,
                 "max": null,
                 "maxlength": null
-            }
+            },
+            "isoLang": "en-US"
         },
         {
             "name": "Number",