Remember old post slugs and automatically redirect to the new slug. fixes #3202

git-svn-id: http://svn.automattic.com/wordpress/trunk@4556 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/admin-functions.php

@@ -2069,6 +2069,43 @@ function wp_reset_vars( $vars ) {
 	}
 }
 
+
+function wp_check_for_changed_slugs($post_id) {
+	if ( !strlen($_POST['wp-old-slug']) )
+		return $post_id;
+
+	$post = &get_post($post_id);
+
+	// we're only concerned with published posts
+	if ( $post->post_status != 'publish' || $post->post_type != 'post' )
+		return $post_id;
+
+	// only bother if the slug has changed
+	if ( $post->post_name == $_POST['wp-old-slug'] )
+		return $post_id;
+
+	$old_slugs = get_post_meta($post_id, '_wp_old_slug');
+
+	// if we haven't added this old slug before, add it now
+	if ( !count($old_slugs) || !in_array($_POST['wp-old-slug'], $old_slugs) )
+		add_post_meta($post_id, '_wp_old_slug', $_POST['wp-old-slug']);
+
+	// if the new slug was used previously, delete it from the list
+	if ( in_array($post->post_name, $old_slugs) )
+		delete_post_meta($post_id, '_wp_old_slug', $post->post_name);
+
+	return $post_id;
+}
+
+
+function wp_remember_old_slug() {
+	global $post;
+	$name = wp_specialchars($post->post_name); // just in case
+	if ( strlen($name) )
+		echo '<input type="hidden" id="wp-old-slug" name="wp-old-slug" value="' . $name . '" />';
+}
+
+
 // If siteurl or home changed, reset cookies and flush rewrite rules.
 function update_home_siteurl( $old_value, $value ) {
 	global $wp_rewrite, $user_login, $user_pass_md5;

wp-admin/upgrade-functions.php

@@ -175,6 +175,9 @@ function upgrade_all() {
 	if ( $wp_current_db_version < 3845 )
 		upgrade_210();
 
+	if ( $wp_current_db_version < 4351 )
+		upgrade_old_slugs();
+
 	$wp_rewrite->flush_rules();
 
 	update_option('db_version', $wp_db_version);
@@ -544,6 +547,13 @@ function upgrade_210() {
 	}
 }
 
+function upgrade_old_slugs() {
+	// upgrade people who were using the Redirect Old Slugs plugin
+	global $wpdb;
+	$wpdb->query("UPDATE $wpdb->postmeta SET meta_key = '_wp_old_slug' WHERE meta_key = 'old_slug'");
+}
+
+
 // The functions we use to actually do stuff
 
 // General

wp-includes/default-filters.php

@@ -146,6 +146,11 @@ add_filter('option_blog_charset', 'wp_specialchars');
 add_filter('mce_plugins', '_mce_load_rtl_plugin');
 add_filter('mce_buttons', '_mce_add_direction_buttons');
 
+// Redirect Old Slugs
+add_action('template_redirect', 'wp_old_slug_redirect');
+add_action('edit_post', 'wp_check_for_changed_slugs');
+add_action('edit_form_advanced', 'wp_remember_old_slug');
+
 // Actions
 add_action('wp_head', 'rsd_link');
 add_action('wp_head', 'locale_stylesheet');

wp-includes/query.php

@@ -1116,6 +1116,40 @@ class WP_Query {
 	}
 }
 
+
+// Redirect old slugs
+function wp_old_slug_redirect () {
+	global $wp_query;
+	if ( is_404() && '' != $wp_query->query_vars['name'] ) :
+		global $wpdb;
+
+		$query = "SELECT post_id FROM $wpdb->postmeta, $wpdb->posts WHERE ID = post_id AND meta_key = '_wp_old_slug' AND meta_value='" . $wp_query->query_vars['name'] . "'";
+
+		// if year, monthnum, or day have been specified, make our query more precise
+		// just in case there are multiple identical _wp_old_slug values
+		if ( '' != $wp_query->query_vars['year'] )
+			$query .= " AND YEAR(post_date) = '{$wp_query->query_vars['year']}'";
+		if ( '' != $wp_query->query_vars['monthnum'] )
+			$query .= " AND MONTH(post_date) = '{$wp_query->query_vars['monthnum']}'";
+		if ( '' != $wp_query->query_vars['day'] )
+			$query .= " AND DAYOFMONTH(post_date) = '{$wp_query->query_vars['day']}'";
+
+		$id = (int) $wpdb->get_var($query);
+
+		if ( !$id )
+			return;
+
+		$link = get_permalink($id);
+
+		if ( !$link )
+			return;
+
+		wp_redirect($link, '301'); // Permanent redirect
+		exit;
+	endif;
+}
+
+
 //
 // Private helper functions
 //

wp-includes/version.php

@@ -3,6 +3,6 @@
 // This holds the version number in a separate file so we can bump it without cluttering the SVN
 
 $wp_version = '2.1-alpha3';
-$wp_db_version = 4350;
+$wp_db_version = 4351;
 
 ?>