fixes #2378

app/models/tag_alias.rb

@@ -198,11 +198,15 @@ class TagAlias < ActiveRecord::Base
 
   def rename_wiki_and_artist
     antecedent_wiki = WikiPage.titled(antecedent_name).first
-    if antecedent_wiki.present? && WikiPage.titled(consequent_name).blank?
-      CurrentUser.scoped(creator, creator_ip_addr) do
-        antecedent_wiki.update_attributes(
-          :title => consequent_name
-        )
+    if antecedent_wiki.present? 
+      if WikiPage.titled(consequent_name).blank?
+        CurrentUser.scoped(creator, creator_ip_addr) do
+          antecedent_wiki.update_attributes(
+            :title => consequent_name
+          )
+        end
+      else
+        update_forum_topic_for_wiki_conflict
       end
     end
 
@@ -249,6 +253,16 @@ class TagAlias < ActiveRecord::Base
     end
   end
 
+  def update_forum_topic_for_wiki_conflict
+    if forum_topic
+      CurrentUser.scoped(User.admins.first, "127.0.0.1") do
+        forum_topic.posts.create(
+          :body => "The tag alias [[#{antecedent_name}]] -> [[#{consequent_name}]] has conflicting wiki pages. [[#{consequent_name}]] should be updated to include information from [[#{antecedent_name}]] if necessary."
+        )
+      end
+    end
+  end
+
   def reject!
     update_column(:status, "deleted")
     clear_all_cache

test/unit/tag_alias_test.rb

@@ -99,6 +99,19 @@ class TagAliasTest < ActiveSupport::TestCase
         @alias = FactoryGirl.create(:tag_alias, :antecedent_name => "aaa", :consequent_name => "bbb", :forum_topic => @topic)
       end
 
+      context "and conflicting wiki pages" do
+        setup do
+          @wiki1 = FactoryGirl.create(:wiki_page, :title => "aaa")
+          @wiki2 = FactoryGirl.create(:wiki_page, :title => "bbb")
+        end
+
+        should "update the topic when processed" do
+          assert_difference("ForumPost.count") do
+            @alias.rename_wiki_and_artist
+          end
+        end
+      end
+
       should "update the topic when processed" do
         assert_difference("ForumPost.count") do
           @alias.process!