From 72e98e4e6ab24df27ecd9b1301e62ab4bfcec474 Mon Sep 17 00:00:00 2001
From: Aryeh Gregor <simetrical@users.mediawiki.org>
Date: Mon, 5 Jan 2009 15:59:46 +0000
Subject: [PATCH] When $wgEnforceHtmlIds=false, add legacy anchors

This means that old links will still work in a lot of cases.  However,
if the legacy anchor is invalid XML, we omit it.  In particular, on
non-Latin wikis, practically all old section links (from external
sources or using external links) are likely to break, since the first
character of legacy anchors starting with a non-ASCII character will be
".", which is invalid in XML as well as in HTML4.
---
 includes/Linker.php        | 14 ++++++--
 includes/parser/Parser.php | 68 +++++++++++++++++++++++++++++++++-----
 2 files changed, 72 insertions(+), 10 deletions(-)

diff --git a/includes/Linker.php b/includes/Linker.php
index 3eddbcc819..f116fb4a03 100644
--- a/includes/Linker.php
+++ b/includes/Linker.php
@@ -1515,11 +1515,21 @@ class Linker {
 	 * @param string $anchor  The anchor to give the headline (the bit after the #)
 	 * @param string $text    The text of the header
 	 * @param string $link    HTML to add for the section edit link
+	 * @param mixed  $legacyAnchor A second, optional anchor to give for
+	 *   backward compatibility (false to omit)
 	 *
 	 * @return string HTML headline
 	 */
-	public function makeHeadline( $level, $attribs, $anchor, $text, $link ) {
-		return "<a name=\"$anchor\" id=\"$anchor\"></a><h$level$attribs$link <span class=\"mw-headline\">$text</span></h$level>";
+	public function makeHeadline( $level, $attribs, $anchor, $text, $link, $legacyAnchor = false ) {
+		$ret = "<a name=\"$anchor\" id=\"$anchor\"></a>"
+			. "<h$level$attribs"
+			. $link
+			. " <span class=\"mw-headline\">$text</span>"
+			. "</h$level>";
+		if ( $legacyAnchor !== false ) {
+			$ret = "<a name=\"$legacyAnchor\" id=\"$legacyAnchor\"></a>$ret";
+		}
+		return $ret;
 	}
 
 	/**
diff --git a/includes/parser/Parser.php b/includes/parser/Parser.php
index 11cbc11d5c..e3ee5e74b2 100644
--- a/includes/parser/Parser.php
+++ b/includes/parser/Parser.php
@@ -3617,14 +3617,60 @@ class Parser
 
 			# Save headline for section edit hint before it's escaped
 			$headlineHint = $safeHeadline;
-			$safeHeadline = Sanitizer::escapeId( $safeHeadline,
-				$wgEnforceHtmlIds ? 'noninitial' : 'xml' );
-			# HTML names must be case-insensitively unique (bug 10721)
+
+			if ( $wgEnforceHtmlIds ) {
+				$legacyHeadline = false;
+				$safeHeadline = Sanitizer::escapeId( $safeHeadline,
+					'noninitial' );
+			} else {
+				# For reverse compatibility, provide an id that's
+				# HTML4-compatible, like we used to.
+				#
+				# It may be worth noting, academically, that it's possible for
+				# the legacy anchor to conflict with a non-legacy headline
+				# anchor on the page.  In this case likely the "correct" thing
+				# would be to either drop the legacy anchors or make sure
+				# they're numbered first.  However, this would require people
+				# to type in section names like "abc_.D7.93.D7.90.D7.A4"
+				# manually, so let's not bother worrying about it.
+				$legacyHeadline = Sanitizer::escapeId( $safeHeadline,
+					'noninitial' );
+				$safeHeadline = Sanitizer::escapeId( $safeHeadline, 'xml' );
+
+				if ( $legacyHeadline == $safeHeadline ) {
+					# No reason to have both (in fact, we can't)
+					$legacyHeadline = false;
+				} elseif ( $legacyHeadline != Sanitizer::escapeId(
+				$legacyHeadline, 'xml' ) ) {
+					# The legacy id is invalid XML.  We used to allow this, but
+					# there's no reason to do so anymore.  Backward
+					# compatibility will fail slightly in this case, but it's
+					# no big deal.
+					$legacyHeadline = false;
+				}
+			}
+
+			# HTML names must be case-insensitively unique (bug 10721).  FIXME:
+			# Does this apply to Unicode characters?  Because we aren't
+			# handling those here.
 			$arrayKey = strtolower( $safeHeadline );
+			if ( $legacyHeadline === false ) {
+				$legacyArrayKey = false;
+			} else {
+				$legacyArrayKey = strtolower( $legacyHeadline );
+			}
 
 			# count how many in assoc. array so we can track dupes in anchors
-			isset( $refers[$arrayKey] ) ? $refers[$arrayKey]++ : $refers[$arrayKey] = 1;
-			$refcount[$headlineCount] = $refers[$arrayKey];
+			if ( isset( $refers[$arrayKey] ) ) {
+				$refers[$arrayKey]++;
+			} else {
+				$refers[$arrayKey] = 1;
+			}
+			if ( isset( $refers[$legacyArrayKey] ) ) {
+				$refers[$legacyArrayKey]++;
+			} else {
+				$refers[$legacyArrayKey] = 1;
+			}
 
 			# Don't number the heading if it is the only one (looks silly)
 			if( $doNumberHeadings && count( $matches[3] ) > 1) {
@@ -3634,8 +3680,12 @@ class Parser
 
 			# Create the anchor for linking from the TOC to the section
 			$anchor = $safeHeadline;
-			if($refcount[$headlineCount] > 1 ) {
-				$anchor .= '_' . $refcount[$headlineCount];
+			$legacyAnchor = $legacyHeadline;
+			if ( $refers[$arrayKey] > 1 ) {
+				$anchor .= '_' . $refers[$arrayKey];
+			}
+			if ( $legacyHeadline !== false && $refers[$legacyArrayKey] > 1 ) {
+				$legacyAnchor .= '_' . $refers[$legacyArrayKey];
 			}
 			if( $enoughToc && ( !isset($wgMaxTocLevel) || $toclevel<$wgMaxTocLevel ) ) {
 				$toc .= $sk->tocLine($anchor, $tocline, $numbering, $toclevel);
@@ -3653,7 +3703,9 @@ class Parser
 			} else {
 				$editlink = '';
 			}
-			$head[$headlineCount] = $sk->makeHeadline( $level, $matches['attrib'][$headlineCount], $anchor, $headline, $editlink );
+			$head[$headlineCount] = $sk->makeHeadline( $level,
+				$matches['attrib'][$headlineCount], $anchor, $headline,
+				$editlink, $legacyAnchor );
 
 			$headlineCount++;
 		}
-- 
2.20.1