From 821505367e41597e23d3547ca70c2485f1d9da26 Mon Sep 17 00:00:00 2001
From: Timo Tijhof <krinklemail@gmail.com>
Date: Sat, 13 Apr 2019 04:27:31 +0100
Subject: [PATCH] title: Allow passing MessageLocalizer to newMainPage()

The method could not be used in session-less endpoints. This was
worked around once in the Startup module.

I plan to use this method in an extension module as well,
and would prefer not to duplicate core's logic for determining
the main page, outside this repository.

As general dependency-injection pattern, it seems desirable
to allow injecting a MessageLocalizer here.

Change-Id: I76cd02b2f489882e9404b93270f76aad9f0a4d9d
---
 includes/Title.php                            | 26 +++++++++++---
 .../ResourceLoaderStartUpModule.php           | 12 ++-----
 tests/phpunit/includes/TitleTest.php          | 35 +++++++++++++++++++
 3 files changed, 60 insertions(+), 13 deletions(-)

diff --git a/includes/Title.php b/includes/Title.php
index 3891c82418..12ab532558 100644
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -623,15 +623,33 @@ class Title implements LinkTarget, IDBAccessObject {
 	/**
 	 * Create a new Title for the Main Page
 	 *
+	 * This uses the 'mainpage' interface message, which could be specified in
+	 * `$wgForceUIMsgAsContentMsg`. If that is the case, then calling this method
+	 * will use the user language, which would involve initialising the session
+	 * via `RequestContext::getMain()->getLanguage()`. For session-less endpoints,
+	 * be sure to pass in a MessageLocalizer (such as your own RequestContext,
+	 * or ResourceloaderContext) to prevent an error.
+	 *
 	 * @note The Title instance returned by this method is not guaranteed to be a fresh instance.
 	 * It may instead be a cached instance created previously, with references to it remaining
 	 * elsewhere.
 	 *
-	 * @return Title The new object
+	 * @param MessageLocalizer|null $localizer An optional context to use (since 1.34)
+	 * @return Title
 	 */
-	public static function newMainPage() {
-		$title = self::newFromText( wfMessage( 'mainpage' )->inContentLanguage()->text() );
-		// Don't give fatal errors if the message is broken
+	public static function newMainPage( MessageLocalizer $localizer = null ) {
+		if ( $localizer ) {
+			$msg = $localizer->msg( 'mainpage' );
+		} else {
+			$msg = wfMessage( 'mainpage' );
+		}
+
+		$title = self::newFromText( $msg->inContentLanguage()->text() );
+
+		// Every page renders at least one link to the Main Page (e.g. sidebar).
+		// If the localised value is invalid, don't produce fatal errors that
+		// would make the wiki inaccessible (and hard to fix the invalid message).
+		// Gracefully fallback...
 		if ( !$title ) {
 			$title = self::newFromText( 'Main Page' );
 		}
diff --git a/includes/resourceloader/ResourceLoaderStartUpModule.php b/includes/resourceloader/ResourceLoaderStartUpModule.php
index acc2503d90..da6063ea89 100644
--- a/includes/resourceloader/ResourceLoaderStartUpModule.php
+++ b/includes/resourceloader/ResourceLoaderStartUpModule.php
@@ -49,15 +49,9 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 	private function getConfigSettings( $context ) {
 		$conf = $this->getConfig();
 
-		// We can't use Title::newMainPage() if 'mainpage' is in
-		// $wgForceUIMsgAsContentMsg because that will try to use the session
-		// user's language and we have no session user. This does the
-		// equivalent but falling back to our ResourceLoaderContext language
-		// instead.
-		$mainPage = Title::newFromText( $context->msg( 'mainpage' )->inContentLanguage()->text() );
-		if ( !$mainPage ) {
-			$mainPage = Title::newFromText( 'Main Page' );
-		}
+		// Passing a context is important as Title::newMainPage() may otherwise
+		// try to intialise a session, which is not allowed on load.php requests.
+		$mainPage = Title::newMainPage( $context );
 
 		/**
 		 * Namespace related preparation
diff --git a/tests/phpunit/includes/TitleTest.php b/tests/phpunit/includes/TitleTest.php
index 149c25bc5f..e29b7e7a3e 100644
--- a/tests/phpunit/includes/TitleTest.php
+++ b/tests/phpunit/includes/TitleTest.php
@@ -2,6 +2,7 @@
 
 use MediaWiki\Linker\LinkTarget;
 use MediaWiki\MediaWikiServices;
+use Wikimedia\TestingAccessWrapper;
 
 /**
  * @group Database
@@ -20,6 +21,12 @@ class TitleTest extends MediaWikiTestCase {
 		$this->setContentLang( 'en' );
 	}
 
+	protected function tearDown() {
+		// For testNewMainPage
+		MessageCache::destroyInstance();
+		parent::tearDown();
+	}
+
 	/**
 	 * @covers Title::legalChars
 	 */
@@ -1097,4 +1104,32 @@ class TitleTest extends MediaWikiTestCase {
 			$firstValue->equals( $secondValue )
 		);
 	}
+
+	/**
+	 * @covers Title::newMainPage
+	 */
+	public function testNewMainPage() {
+		$msgCache = TestingAccessWrapper::newFromClass( MessageCache::class );
+		$msgCache->instance = $this->createMock( MessageCache::class );
+		$msgCache->instance->method( 'get' )->willReturn( 'Foresheet' );
+		$msgCache->instance->method( 'transform' )->willReturn( 'Foresheet' );
+
+		$this->assertSame(
+			'Foresheet',
+			Title::newMainPage()->getText()
+		);
+	}
+
+	/**
+	 * @covers Title::newMainPage
+	 */
+	public function testNewMainPageWithLocal() {
+		$local = $this->createMock( MessageLocalizer::class );
+		$local->method( 'msg' )->willReturn( new RawMessage( 'Prime Article' ) );
+
+		$this->assertSame(
+			'Prime Article',
+			Title::newMainPage( $local )->getText()
+		);
+	}
 }
-- 
2.20.1