Expire Caches for Redirected Links

[[!redirect foo]] should expire all pages which reference "foo".
Sounds simple, but this was a really gnarly bug to fix.

app/models/page.rb

@@ -71,10 +71,6 @@ class Page < ActiveRecord::Base
   def linked_from
     web.select.pages_that_link_to(name)
   end
-  
-  def redirects_for
-    wiki_references.select { |ref| ref.redirected_page?}.map { |ref| ref.referenced_name }
-  end
 
   def included_from
     web.select.pages_that_include(name)

app/models/wiki_reference.rb

@@ -54,14 +54,9 @@ class WikiReference < ActiveRecord::Base
 
   def self.pages_redirected_to(web, page_name)
     names = []
-    if web.has_page?(page_name) 
-      page = web.page(page_name)
-      redirected_names = page.redirects_for
-      redirected_names.each do |name|
-        names = names | self.pages_that_reference(web, name)
-      end
-    end
-    names
+    page = web.page(page_name)
+    Thread.current[:page_redirects][page.name].each { |name| names = names + self.pages_that_reference(web, name) }
+    names.uniq    
   end
 
   def self.page_that_redirects_for(web, page_name)
@@ -70,8 +65,8 @@ class WikiReference < ActiveRecord::Base
       'WHERE wiki_references.referenced_name = ? ' +
       "AND wiki_references.link_type = '#{REDIRECTED_PAGE}' " +
       "AND pages.web_id = '#{web.id}'"
-    names = connection.select_all(sanitize_sql([query, page_name])).map { |row| row['name'] }
-    names[0] 
+    row = connection.select_one(sanitize_sql([query, page_name]))
+    row['name'] if row
   end
   
   def self.pages_in_category(web, category)

app/views/wiki/edit.rhtml

@@ -12,6 +12,9 @@
 	<% form_tag({ :action => 'save', :web => @web.address, :id => @page.name },
 	             { 'id' => 'editForm', 'method' => 'post', 'onsubmit' => 'cleanAuthorName()',
 	               'accept-charset' => 'utf-8' }) do %>
+	   <div>	
+		<textarea name="content" id="content" rows="24" cols="60"><%= h(flash[:content] || 
+                         ((params['content'] && params['content'].is_utf8?) ?  params['content'] : @page.content).purify) %></textarea>
 <% if @page_name != 'HomePage' -%>
 	   <p>
 	      <%= check_box_tag :alter_title, value = "1", checked=false,
@@ -22,9 +25,6 @@
 <% else -%>
        <%= hidden_field_tag 'new_name', @page_name %>
 <% end%> 
-	   <div>	
-		<textarea name="content" id="content" rows="24" cols="60"><%= h(flash[:content] || 
-                         ((params['content'] && params['content'].is_utf8?) ?  params['content'] : @page.content).purify) %></textarea>
 		<div id="editFormButtons">
 			<input type="submit" value="Submit" accesskey="s"/> as 
 			<%= text_field_tag :author, h(@author.purify), 

lib/page_renderer.rb

@@ -179,7 +179,12 @@ class PageRenderer
       references.build :referenced_name => redirected_page_name, 
           :link_type => WikiReference::REDIRECTED_PAGE
     end
-
+    
+    # ugly hack: store these in a thread-local variable, so that the cache-sweeper has access to it.
+    Thread.current[:page_redirects] ?
+      Thread.current[:page_redirects].update({ @revision.page.name => redirects}) :
+      Thread.current[:page_redirects] = { @revision.page.name => redirects}
+    
     categories = rendering_result.find_chunks(Category).map { |cat| cat.list }.flatten
     categories.each do |category|
       references.build :referenced_name => category, :link_type => WikiReference::CATEGORY

test/unit/page_renderer_test.rb

@@ -524,6 +524,7 @@ END_THM
   end
   
   def test_revisions_diff
+    Thread.current[:page_redirects] = { @page.name => []}
     Revision.create(:page => @page, :content => 'What a blue and lovely morning', 
         :author => Author.new('DavidHeinemeierHansson'), :revised_at => Time.now)
     Revision.create(:page => @page, :content => 'What a red and lovely morning today',