wikis: disallow renaming unless tag is empty (fix #2964).

app/models/tag_alias.rb

@@ -254,9 +254,7 @@ class TagAlias < ActiveRecord::Base
     if antecedent_wiki.present? 
       if WikiPage.titled(consequent_name).blank?
         CurrentUser.scoped(creator, creator_ip_addr) do
-          antecedent_wiki.update_attributes(
-            :title => consequent_name
-          )
+          antecedent_wiki.update(title: consequent_name, skip_secondary_validations: true)
         end
       else
         message = "The tag alias [[#{antecedent_name}]] -> [[#{consequent_name}]] (alias ##{id}) has conflicting wiki pages. [[#{consequent_name}]] should be updated to include information from [[#{antecedent_name}]] if necessary."

app/models/wiki_page.rb

@@ -10,9 +10,11 @@ class WikiPage < ActiveRecord::Base
   belongs_to :updater, :class_name => "User"
   validates_uniqueness_of :title, :case_sensitive => false
   validates_presence_of :title
+  validate :validate_rename
   validate :validate_locker_is_builder
   validate :validate_not_locked
-  attr_accessible :title, :body, :is_locked, :is_deleted, :other_names
+  attr_accessor :skip_secondary_validations
+  attr_accessible :title, :body, :is_locked, :is_deleted, :other_names, :skip_secondary_validations
   has_one :tag, :foreign_key => "name", :primary_key => "title"
   has_one :artist, lambda {where(:is_active => true)}, :foreign_key => "name", :primary_key => "title"
   has_many :versions, lambda {order("wiki_page_versions.id ASC")}, :class_name => "WikiPageVersion", :dependent => :destroy
@@ -120,6 +122,15 @@ class WikiPage < ActiveRecord::Base
     end
   end
 
+  def validate_rename
+    return if !title_changed? || skip_secondary_validations
+
+    tag_was = Tag.find_by_name(Tag.normalize_name(title_was))
+    if tag_was.present? && tag_was.post_count > 0
+      errors.add(:title, "cannot be changed: '#{tag_was.name}' still has #{tag_was.post_count} posts. Move the posts and update any wikis linking to this page first.")
+    end
+  end
+
   def revert_to(version)
     if id != version.wiki_page_id
       raise RevertError.new("You cannot revert to a previous version of another wiki page.")
@@ -145,6 +156,10 @@ class WikiPage < ActiveRecord::Base
     self.other_names = normalized_other_names.uniq.join(" ")
   end
 
+  def skip_secondary_validations=(value)
+    @skip_secondary_validations = (value == true || value == "1")
+  end
+
   def creator_name
     User.id_to_name(creator_id).tr("_", " ")
   end