Handle /t/only-the-slug urls by trying to find the topic by slug (second try)

app/controllers/application_controller.rb

@@ -282,6 +282,7 @@ class ApplicationController < ActionController::Base
       @latest = f.order('views desc').take(10)
       @recent = f.order('created_at desc').take(10)
       @slug =  params[:slug].class == String ? params[:slug] : ''
+      @slug =  (params[:id].class == String ? params[:id] : '') if @slug.blank?
       @slug.gsub!('-',' ')
       render status: status, layout: 'no_js', template: '/exceptions/not_found'
     end

app/controllers/topics_controller.rb

@@ -21,19 +21,18 @@ class TopicsController < ApplicationController
 
   before_filter :consider_user_for_promotion, only: :show
 
-  skip_before_filter :check_xhr, only: [:avatar, :show, :feed, :redirect_to_show]
+  skip_before_filter :check_xhr, only: [:avatar, :show, :feed]
   caches_action :avatar, cache_path: Proc.new {|c| "#{c.params[:post_number]}-#{c.params[:topic_id]}" }
 
-  def redirect_to_show
-    topic_query = ((num = params[:id].to_i) > 0 and num.to_s == params[:id].to_s) ? Topic.where(id: num) : Topic.where(slug: params[:id])
-    topic = topic_query.includes(:category).first
-    raise Discourse::NotFound unless topic
-    redirect_to topic.relative_url
-  end
-
   def show
     opts = params.slice(:username_filters, :best_of, :page, :post_number, :posts_before, :posts_after, :best)
+    begin
       @topic_view = TopicView.new(params[:id] || params[:topic_id], current_user, opts)
+    rescue Discourse::NotFound
+      topic = Topic.where(slug: params[:id]).first
+      raise Discourse::NotFound unless topic
+      return redirect_to(topic.relative_url)
+    end
 
     raise Discourse::NotFound if @topic_view.posts.blank? && !(opts[:best].to_i > 0)
 

spec/controllers/topics_controller_spec.rb

@@ -373,6 +373,16 @@ describe TopicsController do
       response.should be_success
     end
 
+    it 'can find a topic given a slug in the id param' do
+      xhr :get, :show, id: topic.slug
+      expect(response).to redirect_to(topic.relative_url)
+    end
+
+    it 'returns 404 when an invalid slug is given and no id' do
+      xhr :get, :show, id: 'nope-nope'
+      expect(response.status).to eq(404)
+    end
+
     it 'records a view' do
       lambda { xhr :get, :show, topic_id: topic.id, slug: topic.slug }.should change(View, :count).by(1)
     end