Support language fallbacks for Special:MyLanguage

Add fallback lookup based on the interface language to
Special:MyLanguage. Lookup order:

  <user lang> -> <explicit lang> -> <fallback lang(s)> -> <base>

Example when the user's lang is arz:

  arz -> <explicit lang> -> ar -> en -> <base>

Bug: T50292
Change-Id: I245cab71fdd4b4585f86dde808493cd69841b09a

diff --git a/includes/specials/SpecialMyLanguage.php b/includes/specials/SpecialMyLanguage.php
index 9cb6d4b..37d96f4 100644 (file)
--- a/includes/specials/SpecialMyLanguage.php
+++ b/includes/specials/SpecialMyLanguage.php
@@ -81,6 +81,7 @@ class SpecialMyLanguage extends RedirectSpecialArticle {
                }
 
                if ( !$base ) {
+                       // No subpage provided or base page does not exist
                        return null;
                }
 
@@ -90,14 +91,38 @@ class SpecialMyLanguage extends RedirectSpecialArticle {
                }
 
                $uiCode = $this->getLanguage()->getCode();
+               $wikiLangCode = $this->getConfig()->get( 'LanguageCode' );
+
+               if ( $uiCode === $wikiLangCode ) {
+                       // Short circuit when the current UI language is the
+                       // wiki's default language to avoid unnecessary page lookups.
+                       return $base;
+               }
+
+               // Check for a subpage in current UI language
                $proposed = $base->getSubpage( $uiCode );
-               if ( $proposed && $proposed->exists() && $uiCode !== $base->getPageLanguage()->getCode() ) {
+               if ( $proposed && $proposed->exists() ) {
                        return $proposed;
-               } elseif ( $provided && $provided->exists() ) {
+               }
+
+               if ( $provided !== $base && $provided->exists() ) {
+                       // Explicit language code given and the page exists
                        return $provided;
-               } else {
-                       return $base;
                }
+
+               // Check for fallback languages specified by the UI language
+               $possibilities = Language::getFallbacksFor( $uiCode );
+               foreach ( $possibilities as $lang ) {
+                       if ( $lang !== $wikiLangCode ) {
+                               $proposed = $base->getSubpage( $lang );
+                               if ( $proposed && $proposed->exists() ) {
+                                       return $proposed;
+                               }
+                       }
+               }
+
+               // When all else has failed, return the base page
+               return $base;
        }
 
        /**

diff --git a/tests/phpunit/includes/specials/SpecialMyLanguageTest.php b/tests/phpunit/includes/specials/SpecialMyLanguageTest.php
index 89fd1b0..84fa71a 100644 (file)
--- a/tests/phpunit/includes/specials/SpecialMyLanguageTest.php
+++ b/tests/phpunit/includes/specials/SpecialMyLanguageTest.php
@@ -8,7 +8,10 @@ class SpecialMyLanguageTest extends MediaWikiTestCase {
        public function addDBDataOnce() {
                $titles = [
                        'Page/Another',
+                       'Page/Another/ar',
+                       'Page/Another/en',
                        'Page/Another/ru',
+                       'Page/Another/zh-hans',
                ];
                foreach ( $titles as $title ) {
                        $page = WikiPage::factory( Title::newFromText( $title ) );
@@ -54,12 +57,22 @@ class SpecialMyLanguageTest extends MediaWikiTestCase {
        }
 
        public static function provideFindTitle() {
+               // See addDBDataOnce() for page declarations
                return [
+                       // [ $expected, $subpage, $langCode, $userLang ]
                        [ null, '::Fail', 'en', 'en' ],
                        [ 'Page/Another', 'Page/Another/en', 'en', 'en' ],
                        [ 'Page/Another', 'Page/Another', 'en', 'en' ],
                        [ 'Page/Another/ru', 'Page/Another', 'en', 'ru' ],
                        [ 'Page/Another', 'Page/Another', 'en', 'es' ],
+                       [ 'Page/Another/zh-hans', 'Page/Another', 'en', 'zh-hans' ],
+                       [ 'Page/Another/zh-hans', 'Page/Another', 'en', 'zh-mo' ],
+                       [ 'Page/Another/en', 'Page/Another', 'de', 'es' ],
+                       [ 'Page/Another/ar', 'Page/Another', 'en', 'ar' ],
+                       [ 'Page/Another/ar', 'Page/Another', 'en', 'arz' ],
+                       [ 'Page/Another/ar', 'Page/Another/de', 'en', 'arz' ],
+                       [ 'Page/Another/ru', 'Page/Another/ru', 'en', 'arz' ],
+                       [ 'Page/Another/ar', 'Page/Another/ru', 'en', 'ar' ],
                ];
        }
 }