Linker: Avoid passing false to Title::newFromText

This is needed because the call to substr() returns false when the string
is only 1 character long, which occurs when parsing degenerate links like
[[:]] and [[::|foo]].

The seemingly unnecessary test for $match[1] !== '' is for forwards
compatibility with PHP 7.

Bug: T121706
Change-Id: Icc19ee990d01958d64b938d298e9a7e1df7181b5

diff --git a/includes/Linker.php b/includes/Linker.php
index 8e79d9c..43df839 100644 (file)
--- a/includes/Linker.php
+++ b/includes/Linker.php
@@ -1449,31 +1449,34 @@ class Linker {
                                        }
                                } else {
                                        # Other kind of link
-                                       if ( preg_match( $wgContLang->linkTrail(), $match[3], $submatch ) ) {
-                                               $trail = $submatch[1];
-                                       } else {
-                                               $trail = "";
-                                       }
-                                       $linkRegexp = '/\[\[(.*?)\]\]' . preg_quote( $trail, '/' ) . '/';
+                                       # Make sure its target is non-empty
                                        if ( isset( $match[1][0] ) && $match[1][0] == ':' ) {
                                                $match[1] = substr( $match[1], 1 );
                                        }
-                                       list( $inside, $trail ) = Linker::splitTrail( $trail );
-
-                                       $linkText = $text;
-                                       $linkTarget = Linker::normalizeSubpageLink( $title, $match[1], $linkText );
-
-                                       $target = Title::newFromText( $linkTarget );
-                                       if ( $target ) {
-                                               if ( $target->getText() == '' && !$target->isExternal()
-                                                       && !$local && $title
-                                               ) {
-                                                       $newTarget = clone $title;
-                                                       $newTarget->setFragment( '#' . $target->getFragment() );
-                                                       $target = $newTarget;
+                                       if ( $match[1] !== false && $match[1] !== '' ) {
+                                               if ( preg_match( $wgContLang->linkTrail(), $match[3], $submatch ) ) {
+                                                       $trail = $submatch[1];
+                                               } else {
+                                                       $trail = "";
                                                }
+                                               $linkRegexp = '/\[\[(.*?)\]\]' . preg_quote( $trail, '/' ) . '/';
+                                               list( $inside, $trail ) = Linker::splitTrail( $trail );
+
+                                               $linkText = $text;
+                                               $linkTarget = Linker::normalizeSubpageLink( $title, $match[1], $linkText );
+
+                                               $target = Title::newFromText( $linkTarget );
+                                               if ( $target ) {
+                                                       if ( $target->getText() == '' && !$target->isExternal()
+                                                               && !$local && $title
+                                                       ) {
+                                                               $newTarget = clone $title;
+                                                               $newTarget->setFragment( '#' . $target->getFragment() );
+                                                               $target = $newTarget;
+                                                       }
 
-                                               $thelink = Linker::makeCommentLink( $target, $linkText . $inside, $wikiId ) . $trail;
+                                                       $thelink = Linker::makeCommentLink( $target, $linkText . $inside, $wikiId ) . $trail;
+                                               }
                                        }
                                }
                                if ( $thelink ) {