#605880 by bleen18 and David_Rothstein: Fix weird bugs with settings and menus after install due to faulty caching.

includes/cache-install.inc

@@ -10,10 +10,7 @@
  * implementation during normal operations would have a negative impact
  * on performance.
  */
-class DrupalFakeCache implements DrupalCacheInterface {
+class DrupalFakeCache extends DrupalDatabaseCache implements DrupalCacheInterface {
-  function __construct($bin) {
-  }
-
   function get($cid) {
     return FALSE;
   }
@@ -22,11 +19,34 @@ class DrupalFakeCache implements DrupalCacheInterface {
     return array();
   }
 
-
   function set($cid, $data, $expire = CACHE_PERMANENT, array $headers = NULL) {
   }
 
   function clear($cid = NULL, $wildcard = FALSE) {
+    // If there is a database cache, attempt to clear it whenever possible. The
+    // reason for doing this is that the database cache can accumulate data
+    // during installation due to any full bootstraps that may occur at the
+    // same time (for example, AJAX requests triggered by the installer). If we
+    // didn't try to clear it whenever this function is called, the data in the
+    // cache would become stale; for example, the installer sometimes calls
+    // variable_set(), which updates the {variable} table and then clears the
+    // cache to make sure that the next page request picks up the new value.
+    // Not actually clearing the cache here therefore leads old variables to be
+    // loaded on the first page requests after installation, which can cause
+    // subtle bugs, some of which would not be fixed unless the site
+    // administrator cleared the cache manually.
+    try {
+      if (function_exists('drupal_install_initialize_database')) {
+        drupal_install_initialize_database();
+        parent::clear($cid, $wildcard);
+      }
+    }
+    // If the attempt at clearing the cache causes an error, that means that
+    // either the database connection is not set up yet or the relevant cache
+    // table in the database has not yet been created, so we can safely do
+    // nothing here.
+    catch (Exception $e) {
+    }
   }
 
   function isEmpty() {