Index: Parser.php
===================================================================
RCS file: /cvsroot/wikipedia/phase3/includes/Parser.php,v
retrieving revision 1.506
diff -u -r1.506 Parser.php
--- Parser.php	20 Sep 2005 18:15:25 -0000	1.506
+++ Parser.php	20 Sep 2005 19:30:22 -0000
@@ -1965,6 +1965,7 @@
 		wfProfileIn( $fname );
 
 		$titleChars = Title::legalChars();
+		$dtitleChars = "$titleChars|{}\[\]"; // [] so that {{{arg|[[foo|bar]]}} will work
 
 		# This function is called recursively. To keep track of arguments we need a stack:
 		array_push( $this->mArgStack, $args );
@@ -1972,9 +1973,12 @@
 		# Variable substitution
 		$text = preg_replace_callback( "/{{([$titleChars]*?)}}/", array( &$this, 'variableSubstitution' ), $text );
 
-		if ( $this->mOutputType == OT_HTML || $this->mOutputType == OT_WIKI ) {
+		if ( $this->mOutputType == OT_WIKI ) {
 			# Argument substitution
-			$text = preg_replace_callback( "/{{{([$titleChars]*?)}}}/", array( &$this, 'argSubstitution' ), $text );
+			$text = preg_replace_callback( "/{{{([$dtitleChars]*?)}}}/", array( &$this, 'argSubstitution' ), $text );
+		} elseif ( $this->mOutputType == OT_HTML ) {
+			# Argument substitution + default argument substitution
+			$text = preg_replace_callback( "/{{{([$dtitleChars]*?)}}}/", array( &$this, 'argSubstitutionWDefaults' ), $text );
 		}
 		# Template substitution
 		$regex = '/(\\n|{)?{{(['.$titleChars.']*)(\\|.*?|)}}/s';
@@ -2419,6 +2423,31 @@
 		if ( array_key_exists( $arg, $inputArgs ) ) {
 			$text = $inputArgs[$arg];
 		}
+		
+		return $text;
+	}
+
+	/**
+	 * Triple brace replacement with default arguments-- used for template arguments
+	 * @access private
+	 */
+	function argSubstitutionWDefaults( $matches ) {
+		$arg = trim( $matches[1] );
+		
+		if ( strpos( $arg, '|' ) !== false ) {
+			list( $arg, $default ) = explode( '|', $arg, 2 );
+			$arg = rtrim( $arg );
+			$default = ltrim( $default );
+		} else 
+			$default = null;
+
+		$text = $matches[0];
+		$inputArgs = end( $this->mArgStack );
+
+		if ( array_key_exists( $arg, $inputArgs ) ) {
+			$text = $inputArgs[$arg];
+		} else if ( $default !== null )
+			$text = $default;
 
 		return $text;
 	}