Emit a warning message if a single page has multiple conflicting {{DEFAULTSORT:}} keys.

(Also, replace wfMsg() with wfMsgForContent() for the unknown_extension_tag message.)

RELEASE-NOTES

@@ -302,6 +302,8 @@ The following extensions are migrated into MediaWiki 1.14:
 * (bug 16160) Suggestions box should be resized from left for RTL wikis
 * (bug 11533) Fixed insane slowdown when in read-only mode for long periods
   of time with CACHE_NONE (default objectcache table configuration).
+* Trying to set two different default category sort keys for one page now produces
+  a warning
 
 === API changes in 1.14 ===
 

includes/parser/CoreParserFunctions.php

@@ -330,9 +330,18 @@ class CoreParserFunctions {
 
 	public static function defaultsort( $parser, $text ) {
 		$text = trim( $text );
-		if( strlen( $text ) > 0 )
-			$parser->setDefaultSort( $text );
-		return '';
+		if( strlen( $text ) == 0 )
+			return '';
+		$old = $parser->getCustomDefaultSort();
+		$parser->setDefaultSort( $text );
+		if( $old === false || $old == $text )
+			return '';
+		else
+			return( '<span class="error">' .
+				wfMsgForContent( 'duplicate_defaultsort',
+						 htmlspecialchars( $old ),
+						 htmlspecialchars( $text ) ) .
+				'</span>' );
 	}
 
 	public static function filepath( $parser, $name='', $option='' ) {
@@ -367,7 +376,7 @@ class CoreParserFunctions {
 		$stripList = $parser->getStripList();
 		if ( !in_array( $tagName, $stripList ) ) {
 			return '<span class="error">' .
-				wfMsg( 'unknown_extension_tag', $tagName ) .
+				wfMsgForContent( 'unknown_extension_tag', $tagName ) .
 				'</span>';
 		}
 

includes/parser/Parser.php

@@ -4713,6 +4713,16 @@ class Parser
 		}
 	}
 
+	/**
+	 * Accessor for $mDefaultSort
+	 * Unlike getDefaultSort(), will return false if none is set
+	 *
+	 * @return string or false
+	 */
+	public function getCustomDefaultSort() {
+		return $this->mDefaultSort;
+	}
+
 	/**
 	 * Try to guess the section anchor name based on a wikitext fragment
 	 * presumably extracted from a heading, for example "Header" from

languages/messages/MessagesEn.php

@@ -3661,6 +3661,7 @@ You can also [[Special:Watchlist/edit|use the standard editor]].',
 
 # Core parser functions
 'unknown_extension_tag' => 'Unknown extension tag "$1"',
+'duplicate_defaultsort' => 'Warning: Default sort key "$2" overrides earlier default sort key "$1".',
 
 # Special:Version
 'version'                          => 'Version', # Not used as normal message but as header for the special page itself