MDLSITE-6364 Fix displayed parent of English grand-child language packs

It was not correct to assume that all language packs with code starting
with 'en_' would have 'en' as their parent language. For example, the
'en_us_k12' has 'en_us' as parent.

Author: mudrd8mz

classes/stats_manager.php

@@ -360,8 +360,8 @@ public function get_language_pack_ratio_stats(?int $vercode = null): array {
                 continue;
             }
 
-            if (substr($langpack->langcode, 0, 3) === 'en_') {
-                $parent = 'en';
+            if ($langpack->langcode === 'en') {
+                $parent = '';
 
             } else {
                 $langconfig = mlang_component::from_snapshot('langconfig', $langpack->langcode, $version);

tests/stats_manager_test.php

@@ -244,22 +244,29 @@ public function test_get_language_pack_download_page_data() {
         $this->helper_add_language('cs', 'Czech', 'Čeština');
         $this->helper_add_language('de_du', 'German (personal)', 'Deutsch (Du)', 'de');
         $this->helper_add_language('de', 'German', 'Deutsch');
+        $this->helper_add_language('en_us', 'English (US)', 'English (US)', 'en');
+        $this->helper_add_language('en_us_k12', 'English (US) K12', 'English (US) K12', 'en_us');
 
         $statsman->update_stats('400', 'en', 'moodle', 10);
         $statsman->update_stats('400', 'de_du', 'moodle', 1);
         $statsman->update_stats('400', 'cs', 'moodle', 9);
         $statsman->update_stats('400', 'de', 'moodle', 10);
+        $statsman->update_stats('400', 'en_us', 'moodle', 2);
+        $statsman->update_stats('400', 'en_us_k12', 'moodle', 3);
 
         $data = $statsman->get_language_pack_download_page_data(400);
 
-        $this->assertEquals(4, count($data));
+        $this->assertEquals(6, count($data));
         $this->assertEquals('cs', $data[0]['langcode']);
         $this->assertEquals('Czech / Čeština', $data[0]['langname']);
         $this->assertEquals('9', $data[0]['totalstrings']);
         $this->assertEquals('en', $data[1]['langcode']);
-        $this->assertEquals('de', $data[2]['langcode']);
-        $this->assertEquals('de_du', $data[3]['langcode']);
-        $this->assertEquals('de', $data[3]['parentlanguagecode']);
+        $this->assertEquals('en_us', $data[2]['langcode']);
+        $this->assertEquals('en_us_k12', $data[3]['langcode']);
+        $this->assertEquals('en_us', $data[3]['parentlanguagecode']);
+        $this->assertEquals('de', $data[4]['langcode']);
+        $this->assertEquals('de_du', $data[5]['langcode']);
+        $this->assertEquals('de', $data[5]['parentlanguagecode']);
     }
 
     /**