Fix installer issues introduces by MediaWikiServices

This fixes three issues with the installer:

1) Make sure LocalizationCache can find the installer's i18n files.
2) Make sure we don't try to use an SqlBagOStuff for caching before we have
   a functioning database.
3) Don't try to output HTML when redirecting (this is unrelated to
   MediaWikiServices, but came up during testing)

Bug: T135169
Change-Id: I7caa932024cd771d6fa226a3ac6001c3148ecc9c

1 files changed, 29 insertions, 0 deletions

diff --git a/includes/cache/CacheDependency.php b/includes/cache/CacheDependency.php
index 2d29d8651306..a59ba97d0a00 100644
--- a/includes/cache/CacheDependency.php
+++ b/includes/cache/CacheDependency.php
@@ -20,6 +20,7 @@
  * @file
  * @ingroup Cache
  */
+use MediaWiki\MediaWikiServices;
 
 /**
  * This class stores an arbitrary value along with its dependencies.
@@ -247,6 +248,34 @@ class GlobalDependency extends CacheDependency {
 /**
  * @ingroup Cache
  */
+class MainConfigDependency extends CacheDependency {
+	private $name;
+	private $value;
+
+	function __construct( $name ) {
+		$this->name = $name;
+		$this->value = $this->getConfig()->get( $this->name );
+	}
+
+	private function getConfig() {
+		return MediaWikiServices::getInstance()->getMainConfig();
+	}
+
+	/**
+	 * @return bool
+	 */
+	function isExpired() {
+		if ( !$this->getConfig()->has( $this->name ) ) {
+			return true;
+		}
+
+		return $this->getConfig()->get( $this->name ) != $this->value;
+	}
+}
+
+/**
+ * @ingroup Cache
+ */
 class ConstantDependency extends CacheDependency {
 	private $name;
 	private $value;