MDL-67515 tool_customlang: Ignore invalid component strings

After uninstalling a plugin, the translated strings remain in
tool_customlang table, throwing an exception when trying to localise
any strings. Currently there is no mechanism to
clean up customlang tables and files during the uninstall process,
so with this patch the invalid components will be ignored.

admin/tool/customlang/locallib.php

@@ -39,7 +39,7 @@ class tool_customlang_utils {
     const ROUGH_NUMBER_OF_STRINGS = 16500;
 
     /** @var array cache of {@link self::list_components()} results */
-    protected static $components = null;
+    private static $components = null;
 
     /**
      * This class can not be instantiated
@@ -54,28 +54,30 @@ private function __construct() {
      */
     public static function list_components() {
 
-        $list['moodle'] = 'core';
+        if (self::$components === null) {
+            $list['moodle'] = 'core';
 
-        $coresubsystems = core_component::get_core_subsystems();
-        ksort($coresubsystems); // should be but just in case
-        foreach ($coresubsystems as $name => $location) {
-            $list[$name] = 'core_'.$name;
-        }
+            $coresubsystems = core_component::get_core_subsystems();
+            ksort($coresubsystems); // Should be but just in case.
+            foreach ($coresubsystems as $name => $location) {
+                $list[$name] = 'core_' . $name;
+            }
 
-        $plugintypes = core_component::get_plugin_types();
-        foreach ($plugintypes as $type => $location) {
-            $pluginlist = core_component::get_plugin_list($type);
-            foreach ($pluginlist as $name => $ununsed) {
-                if ($type == 'mod') {
-                    // Plugin names are now automatically validated.
-                    $list[$name] = $type.'_'.$name;
-                } else {
-                    $list[$type.'_'.$name] = $type.'_'.$name;
+            $plugintypes = core_component::get_plugin_types();
+            foreach ($plugintypes as $type => $location) {
+                $pluginlist = core_component::get_plugin_list($type);
+                foreach ($pluginlist as $name => $ununsed) {
+                    if ($type == 'mod') {
+                        // Plugin names are now automatically validated.
+                        $list[$name] = $type . '_' . $name;
+                    } else {
+                        $list[$type . '_' . $name] = $type . '_' . $name;
+                    }
                 }
             }
+            self::$components = $list;
         }
-
-        return $list;
+        return self::$components;
     }
 
     /**
@@ -211,14 +213,18 @@ public static function checkin($lang) {
             return false;
         }
 
-        // get all customized strings from updated components
+        list($insql, $inparams) = $DB->get_in_or_equal(self::list_components());
+
+        // Get all customized strings from updated valid components.
         $sql = "SELECT s.*, c.name AS component
                   FROM {tool_customlang} s
                   JOIN {tool_customlang_components} c ON s.componentid = c.id
                  WHERE s.lang = ?
                        AND (s.local IS NOT NULL OR s.modified = 1)
+                       AND c.name $insql
               ORDER BY componentid, stringid";
-        $strings = $DB->get_records_sql($sql, array($lang));
+        array_unshift($inparams, $lang);
+        $strings = $DB->get_records_sql($sql, $inparams);
 
         $files = array();
         foreach ($strings as $string) {
@@ -336,11 +342,9 @@ protected static function dump_strings($lang, $component, $strings) {
      * @return string|boolean filename eg 'moodle.php' or 'workshop.php', false if not found
      */
     protected static function get_component_filename($component) {
-        if (is_null(self::$components)) {
-            self::$components = self::list_components();
-        }
+
         $return = false;
-        foreach (self::$components as $legacy => $normalized) {
+        foreach (self::list_components() as $legacy => $normalized) {
             if ($component === $normalized) {
                 $return = $legacy.'.php';
                 break;