From 337311662d344c90590ca5cee34b8a87da933430 Mon Sep 17 00:00:00 2001
From: daniel <dkinzler@wikimedia.org>
Date: Wed, 23 Jan 2019 11:17:21 +0100
Subject: [PATCH] Fix Title::getFragmentForURL for bad interwiki prefix.

Calling Title::getLinkURL or any other method that relies on
getFragmentForURL on a title with an unknown interwiki prefix
was triggering a fatal error. With this patch, that situation is
handled more gracefully.

Bug: T204800
Change-Id: I665cd5e983a80c15c68c89541d9c856082c460bb
---
 includes/Title.php                          |  12 ++-
 tests/phpunit/includes/TitleMethodsTest.php | 108 ++++++++++++++++++++
 2 files changed, 116 insertions(+), 4 deletions(-)

diff --git a/includes/Title.php b/includes/Title.php
index 34966686b9..1bb54df6f9 100644
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -1609,11 +1609,15 @@ class Title implements LinkTarget, IDBAccessObject {
 	public function getFragmentForURL() {
 		if ( !$this->hasFragment() ) {
 			return '';
-		} elseif ( $this->isExternal()
-			&& !self::getInterwikiLookup()->fetch( $this->mInterwiki )->isLocal()
-		) {
-			return '#' . Sanitizer::escapeIdForExternalInterwiki( $this->mFragment );
+		} elseif ( $this->isExternal() ) {
+			// Note: If the interwiki is unknown, it's treated as a namespace on the local wiki,
+			// so we treat it like a local interwiki.
+			$interwiki = self::getInterwikiLookup()->fetch( $this->mInterwiki );
+			if ( $interwiki && !$interwiki->isLocal() ) {
+				return '#' . Sanitizer::escapeIdForExternalInterwiki( $this->mFragment );
+			}
 		}
+
 		return '#' . Sanitizer::escapeIdForLink( $this->mFragment );
 	}
 
diff --git a/tests/phpunit/includes/TitleMethodsTest.php b/tests/phpunit/includes/TitleMethodsTest.php
index 44d440f3ec..25dc9b3e30 100644
--- a/tests/phpunit/includes/TitleMethodsTest.php
+++ b/tests/phpunit/includes/TitleMethodsTest.php
@@ -1,5 +1,6 @@
 <?php
 
+use MediaWiki\Interwiki\InterwikiLookup;
 use MediaWiki\MediaWikiServices;
 
 /**
@@ -353,6 +354,113 @@ class TitleMethodsTest extends MediaWikiLangTestCase {
 		$this->assertEquals( 0, $linkCache->getGoodLinkID( 'Foo' ), 'link cache should be empty' );
 	}
 
+	public function provideGetLinkURL() {
+		yield 'Simple' => [
+			'/wiki/Goats',
+			NS_MAIN,
+			'Goats'
+		];
+
+		yield 'Fragment' => [
+			'/wiki/Goats#Goatificatiön',
+			NS_MAIN,
+			'Goats',
+			'Goatificatiön'
+		];
+
+		yield 'Unknown interwiki with fragment' => [
+			'https://xx.wiki.test/wiki/xyzzy:Goats#Goatificatiön',
+			NS_MAIN,
+			'Goats',
+			'Goatificatiön',
+			'xyzzy'
+		];
+
+		yield 'Interwiki with fragment' => [
+			'https://acme.test/Goats#Goatificati.C3.B6n',
+			NS_MAIN,
+			'Goats',
+			'Goatificatiön',
+			'acme'
+		];
+
+		yield 'Interwiki with query' => [
+			'https://acme.test/Goats?a=1&b=blank+blank#Goatificati.C3.B6n',
+			NS_MAIN,
+			'Goats',
+			'Goatificatiön',
+			'acme',
+			[
+				'a' => 1,
+				'b' => 'blank blank'
+			]
+		];
+
+		yield 'Local interwiki with fragment' => [
+			'https://yy.wiki.test/wiki/Goats#Goatificatiön',
+			NS_MAIN,
+			'Goats',
+			'Goatificatiön',
+			'yy'
+		];
+	}
+
+	/**
+	 * @dataProvider provideGetLinkURL
+	 *
+	 * @covers Title::getLinkURL
+	 * @covers Title::getFullURL
+	 * @covers Title::getLocalURL
+	 * @covers Title::getFragmentForURL
+	 */
+	public function testGetLinkURL(
+		$expected,
+		$ns,
+		$title,
+		$fragment = '',
+		$interwiki = '',
+		$query = '',
+		$query2 = false,
+		$proto = false
+	) {
+		$this->setMwGlobals( [
+			'wgServer' => 'https://xx.wiki.test',
+			'wgArticlePath' => '/wiki/$1',
+			'wgExternalInterwikiFragmentMode' => 'legacy',
+			'wgFragmentMode' => [ 'html5', 'legacy' ]
+		] );
+
+		$interwikiLookup = $this->getMock( InterwikiLookup::class );
+
+		$interwikiLookup->method( 'fetch' )
+			->willReturnCallback( function ( $interwiki ) {
+				switch ( $interwiki ) {
+					case '':
+						return null;
+					case 'acme':
+						return new Interwiki(
+							'acme',
+							'https://acme.test/$1'
+						);
+					case 'yy':
+						return new Interwiki(
+							'yy',
+							'https://yy.wiki.test/wiki/$1',
+							'/w/api.php',
+							'yywiki',
+							true
+						);
+					default:
+						return false;
+				}
+			} );
+
+		$this->setService( 'InterwikiLookup', $interwikiLookup );
+
+		$title = Title::makeTitle( $ns, $title, $fragment, $interwiki );
+		$this->assertSame( $expected, $title->getLinkURL( $query, $query2, $proto ) );
+	}
+
 	function tearDown() {
 		Title::clearCaches();
 		parent::tearDown();
-- 
2.20.1