From 4de667f3c2dd2fea0f246a313a9ed848a793ed2f Mon Sep 17 00:00:00 2001
From: Kunal Mehta <legoktm@member.fsf.org>
Date: Thu, 28 Jul 2016 14:44:06 -0700
Subject: [PATCH] maintenance: Allow having a nicer error message if an
 extension isn't enabled

Maintenance scripts can be invoked regardless of whether an extension is
enabled on a wiki or not. On wiki farms where some wikis may have an
extension or not, this can potentially be rather confusing. Especially
when the script bails out with a fatal class missing error or a database
table missing.

This allows maintenance scripts to specify that they require an
extension by calling:
 $this->requireExtension( 'ExtensionName' );
in the script's constructor.

Bug: T141531
Change-Id: Icfbf063bb9c9ac9e55c3a5a8ed815528a2c1ce1e
---
 RELEASE-NOTES-1.28            |  2 ++
 maintenance/Maintenance.php   | 42 +++++++++++++++++++++++++++++++++++
 maintenance/doMaintenance.php |  3 +++
 3 files changed, 47 insertions(+)

diff --git a/RELEASE-NOTES-1.28 b/RELEASE-NOTES-1.28
index cff734b796..41e94be634 100644
--- a/RELEASE-NOTES-1.28
+++ b/RELEASE-NOTES-1.28
@@ -36,6 +36,8 @@ production.
 * Added a new hook, 'UploadVerifyUpload', which can be used to reject a file
   upload. Unlike 'UploadVerifyFile' it provides information about upload comment
   and the file description page, but does not run for uploads to stash.
+* (T141604) Extensions can now provide a better error message when their
+  maintenance scripts are run without the extension being installed.
 
 === External library changes in 1.28 ===
 
diff --git a/maintenance/Maintenance.php b/maintenance/Maintenance.php
index 27d816115e..8368aabebb 100644
--- a/maintenance/Maintenance.php
+++ b/maintenance/Maintenance.php
@@ -123,6 +123,12 @@ abstract class Maintenance {
 	 */
 	private $config;
 
+	/**
+	 * @see Maintenance::requireExtension
+	 * @var array
+	 */
+	private $requiredExtensions = [];
+
 	/**
 	 * Used to read the options in the order they were passed.
 	 * Useful for option chaining (Ex. dumpBackup.php). It will
@@ -506,6 +512,42 @@ abstract class Maintenance {
 		$this->config = $config;
 	}
 
+	/**
+	 * Indicate that the specified extension must be
+	 * loaded before the script can run.
+	 *
+	 * This *must* be called in the constructor.
+	 *
+	 * @since 1.28
+	 * @param string $name
+	 */
+	protected function requireExtension( $name ) {
+		$this->requiredExtensions[] = $name;
+	}
+
+	/**
+	 * Verify that the required extensions are installed
+	 *
+	 * @since 1.28
+	 */
+	public function checkRequiredExtensions() {
+		$registry = ExtensionRegistry::getInstance();
+		$missing = [];
+		foreach ( $this->requiredExtensions as $name ) {
+			if ( !$registry->isLoaded( $name ) ) {
+				$missing[] = $name;
+			}
+		}
+
+		if ( $missing ) {
+			$joined = implode( ', ', $missing );
+			$msg = "The following extensions are required to be installed "
+				. "for this script to run: $joined. Please enable them and then try again.";
+			$this->error( $msg, 1 );
+		}
+
+	}
+
 	/**
 	 * Run a child maintenance script. Pass all of the current arguments
 	 * to it.
diff --git a/maintenance/doMaintenance.php b/maintenance/doMaintenance.php
index 000e5f9f08..1272ca221a 100644
--- a/maintenance/doMaintenance.php
+++ b/maintenance/doMaintenance.php
@@ -99,6 +99,9 @@ require_once "$IP/includes/Setup.php";
 // Initialize main config instance
 $maintenance->setConfig( ConfigFactory::getDefaultInstance()->makeConfig( 'main' ) );
 
+// Sanity-check required extensions are installed
+$maintenance->checkRequiredExtensions();
+
 // Do the work
 $maintenance->execute();
 
-- 
2.20.1