From a8c79f3d529db9d82d3740cf0a306d89b6ead2b3 Mon Sep 17 00:00:00 2001
From: Jan Drewniak <jan.drewniak@gmail.com>
Date: Wed, 15 Jul 2020 23:27:09 +0200
Subject: [PATCH] Add config to disable sidebar state persistence for logged-in
 users.

Bug: T255727
Change-Id: Id28e0bc5249ba68b5de2a078a259e9964f619ef7
---
 includes/Constants.php               |  5 +++++
 includes/Hooks.php                   | 28 ++++++++++++++++++++++++++++
 resources/skins.vector.js/sidebar.js |  3 +--
 skin.json                            |  7 ++++++-
 4 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/includes/Constants.php b/includes/Constants.php
index 0441d81ad..3e22aa614 100644
--- a/includes/Constants.php
+++ b/includes/Constants.php
@@ -104,6 +104,11 @@ final class Constants {
 	 */
 	public const FEATURE_LATEST_SKIN = 'LatestSkin';
 
+	/**
+	 * @var string
+	 */
+	public const CONFIG_KEY_DISABLE_SIDEBAR_PERSISTENCE = 'VectorDisableSidebarPersistence';
+
 	// These are used for query parameters.
 	/**
 	 * Override the skin version user preference and site Config. See readme.
diff --git a/includes/Hooks.php b/includes/Hooks.php
index 01f5e8029..f1c282dd9 100644
--- a/includes/Hooks.php
+++ b/includes/Hooks.php
@@ -224,6 +224,34 @@ class Hooks {
 		}
 	}
 
+	/**
+	 * NOTE: Please use ResourceLoaderGetConfigVars hook instead if possible
+	 * for adding config to the page.
+	 * Adds config variables to JS that depend on current page/request.
+	 *
+	 * Adds a config flag that can disable saving the VectorSidebarVisible
+	 * user preference when the sidebar menu icon is clicked.
+	 *
+	 * @param array &$vars Array of variables to be added into the output.
+	 * @param OutputPage $out OutputPage instance calling the hook
+	 */
+	public static function onMakeGlobalVariablesScript( &$vars, OutputPage $out ) {
+		if ( $out->getSkin() instanceof SkinVector ) {
+			$skinVersionLookup = new SkinVersionLookup(
+				$out->getRequest(),
+				$out->getUser(),
+				self::getServiceConfig()
+			);
+
+			if ( !$skinVersionLookup->isLegacy() ) {
+				$vars[ 'wgVectorDisableSidebarPersistence' ] =
+				self::getConfig(
+					Constants::CONFIG_KEY_DISABLE_SIDEBAR_PERSISTENCE
+				);
+			}
+		}
+	}
+
 	/**
 	 * Get a configuration variable such as `Constants::CONFIG_KEY_SHOW_SKIN_PREFERENCES`.
 	 *
diff --git a/resources/skins.vector.js/sidebar.js b/resources/skins.vector.js/sidebar.js
index dda1f1f33..e9a4a1ba6 100644
--- a/resources/skins.vector.js/sidebar.js
+++ b/resources/skins.vector.js/sidebar.js
@@ -79,8 +79,7 @@ function init( window ) {
 		button = window.document.getElementById( SIDEBAR_BUTTON_ID );
 
 	initCheckboxHack( checkbox, button );
-
-	if ( mw.config.get( 'wgUserName' ) ) {
+	if ( mw.config.get( 'wgUserName' ) && !mw.config.get( 'wgVectorDisableSidebarPersistence' ) ) {
 		bindSidebarClickEvent( checkbox, button );
 	}
 }
diff --git a/skin.json b/skin.json
index eacab0ea8..6da39c85f 100644
--- a/skin.json
+++ b/skin.json
@@ -37,7 +37,8 @@
 		"PreferencesFormPreSave": "Vector\\Hooks::onPreferencesFormPreSave",
 		"SkinTemplateNavigation": "Vector\\Hooks::onSkinTemplateNavigation",
 		"LocalUserCreated": "Vector\\Hooks::onLocalUserCreated",
-		"OutputPageBodyAttributes": "Vector\\Hooks::onOutputPageBodyAttributes"
+		"OutputPageBodyAttributes": "Vector\\Hooks::onOutputPageBodyAttributes",
+		"MakeGlobalVariablesScript": "Vector\\Hooks::onMakeGlobalVariablesScript"
 	},
 	"@note": "When modifying skins.vector.styles definition, make sure the installer still works",
 	"ResourceModules": {
@@ -164,6 +165,10 @@
 		"VectorLayoutMaxWidth": {
 			"value": false,
 			"description": "@var boolean Enables the max-width layout for the latest version of Vector. This is intended to be a very short-lived feature flag whose sole purpose is to derisk the deployment of T246420. It should be removed (and made the default) as quickly as possible."
+		},
+		"VectorDisableSidebarPersistence": {
+			"value": false,
+			"description": "@var boolean Temporary feature flag that disables saving the sidebar expanded/collapsed state as a user-preference (triggered via clicking the main menu icon). This is intended as a temporary kill-switch in the event that the DB is overloaded with writes to the user_options table."
 		}
 	},
 	"ServiceWiringFiles": [