upload: Fix incorrect handling of missing file extension in UploadStash

The problematic code:

  $extensions = explode( ' ', $magic->getExtensionsForType( $mimeType ) );
  if ( count( $extensions ) ) {
    $extension = $extensions[0];
  }

If $mimeType is not known to MediaWiki,
   $magic->getExtensionsForType($mimeType) will return null.
explode( ' ', null ) is [""]. (Thank you so much, PHP!)
This means $extensions is nonempty (it contains the empty string), so
$extension is set to ''.

Change-Id: Icf387a9c93cb7351c2f48c69f413e7ad2224ba6b

includes/upload/UploadStash.php

@@ -485,9 +485,9 @@ class UploadStash {
 			// If not, assume that it should be related to the MIME type of the original file.
 			$magic = MediaWiki\MediaWikiServices::getInstance()->getMimeAnalyzer();
 			$mimeType = $magic->guessMimeType( $path );
-			$extensions = explode( ' ', $magic->getExtensionsForType( $mimeType ) );
-			if ( count( $extensions ) ) {
-				$extension = $extensions[0];
+			$extensions = $magic->getExtensionsForType( $mimeType );
+			if ( $extensions !== null ) {
+				$extension = strtok( $extensions, ' ' );
 			}
 		}
 

tests/phpunit/includes/upload/UploadStashTest.php

@@ -40,21 +40,14 @@ class UploadStashTest extends MediaWikiTestCase {
 		];
 	}
 
-	/**
-	 * @todo give this test a real name explaining what is being tested here
-	 */
-	public function testT31408() {
+	public function testExceptionNoFileExtension() {
 		$this->setMwGlobals( 'wgUser', self::$users['uploader']->getUser() );
 
 		$repo = MediaWikiServices::getInstance()->getRepoGroup()->getLocalRepo();
 		$stash = new UploadStash( $repo );
 
-		// Throws exception caught by PHPUnit on failure
+		$this->expectExceptionMessage( wfMessage( 'uploadstash-no-extension' )->text() );
 		$file = $stash->stashFile( $this->tmpFile );
-		// We'll never reach this point if we hit T31408
-		$this->assertTrue( true, 'Unrecognized file without extension' );
-
-		$stash->removeFile( $file->getFileKey() );
 	}
 
 	public static function provideInvalidRequests() {
@@ -99,9 +92,6 @@ class UploadStashTest extends MediaWikiTestCase {
 		$mockRepo = $this->getMockBuilder( FileRepo::class )
 			->disableOriginalConstructor()
 			->getMock();
-		$mockRepo->expects( $this->once() )
-			->method( 'storeTemp' )
-			->willReturn( $mockRepoStoreStatusResult );
 
 		$stash = new UploadStash( $mockRepo );
 		try {