From 4ffebd80f2205da4bc96d05f5101b2ea72895e5a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartosz=20Dziewo=C5=84ski?= <matma.rex@gmail.com>
Date: Tue, 16 Aug 2022 20:11:05 +0200
Subject: [PATCH] Add config option to enable/disable permalinks backend

From in-person code review with Amir: using tableExists() is a bad
idea, because the table might not consistently exists on all replicas.
It's better to have a config option despite the inconvenience.

Bug: T315353
Change-Id: I728759634c454c0dcbdc4603c15cab60415c7c03
---
 extension.json               |  4 ++++
 includes/ThreadItemStore.php | 13 +++++--------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/extension.json b/extension.json
index 3f094d927..36729fb04 100644
--- a/extension.json
+++ b/extension.json
@@ -620,6 +620,10 @@
 			"value": "default",
 			"description": "Override availability of DiscussionTools visual enhancements's reply buttons sub-feature. 'default', 'available', or 'unavailable'."
 		},
+		"DiscussionToolsEnablePermalinksBackend": {
+			"value": true,
+			"description": "Enable the permalinks backend. Do not enable this unless the database tables exist."
+		},
 		"DiscussionToolsAutoTopicSubEditor": {
 			"value": "discussiontoolsapi",
 			"description": "Editor which triggers automatic topic subscriptions. Either 'discussiontoolsapi' for edits made using DiscussionTools' API (e.g. reply and new topic tools), or 'any' for any editor."
diff --git a/includes/ThreadItemStore.php b/includes/ThreadItemStore.php
index 195c88ea3..e2d7d3d71 100644
--- a/includes/ThreadItemStore.php
+++ b/includes/ThreadItemStore.php
@@ -16,9 +16,9 @@ use MWTimestamp;
 use ReadOnlyMode;
 use stdClass;
 use TitleFormatter;
+use Wikimedia\Rdbms\IDatabase;
 use Wikimedia\Rdbms\ILBFactory;
 use Wikimedia\Rdbms\ILoadBalancer;
-use Wikimedia\Rdbms\IMaintainableDatabase;
 use Wikimedia\Rdbms\IResultWrapper;
 use Wikimedia\Rdbms\SelectQueryBuilder;
 
@@ -81,19 +81,16 @@ class ThreadItemStore {
 	 * @return bool
 	 */
 	private function isDisabled(): bool {
-		static $tablesCreated = null;
-		if ( $tablesCreated === null ) {
-			$tablesCreated = $this->getConnectionRef( DB_REPLICA )->tableExists( 'discussiontools_items', __METHOD__ );
-		}
-		return !$tablesCreated;
+		$dtConfig = $this->configFactory->makeConfig( 'discussiontools' );
+		return !$dtConfig->get( 'DiscussionToolsEnablePermalinksBackend' );
 	}
 
 	/**
 	 * @param int $dbIndex DB_PRIMARY or DB_REPLICA
 	 *
-	 * @return IMaintainableDatabase
+	 * @return IDatabase
 	 */
-	private function getConnectionRef( int $dbIndex ): IMaintainableDatabase {
+	private function getConnectionRef( int $dbIndex ): IDatabase {
 		return $this->loadBalancer->getConnectionRef( $dbIndex, [ 'watchlist' ] );
 	}