Fix root redirects stripping the #fragment from the original URL

assets/javascripts/app/router.coffee

@@ -107,16 +107,23 @@ class app.Router
     if (path = location.pathname.replace /^\/{2,}/g, '/') isnt location.pathname
       page.replace path + location.search + location.hash, null, true
 
-    # When the path is "/#/path", replace it with "/path"
+    if @isRoot()
-    if @isRoot() and path = @getInitialPath()
+      if path = @getInitialPathFromHash()
         page.replace path + location.search, null, true
+      else if path = @getInitialPathFromCookie()
+        page.replace path + location.search + location.hash, null, true
     return
 
-  getInitialPath: ->
+  getInitialPathFromHash: ->
     try
       (new RegExp "#/(.+)").exec(decodeURIComponent location.hash)?[1]
     catch
 
+  getInitialPathFromCookie: ->
+    if path = Cookies.get('initial_path')
+      Cookies.expire('initial_path')
+      path
+
   replaceHash: (hash) ->
     page.replace location.pathname + location.search + (hash or ''), null, true
     return

lib/app.rb

@@ -157,6 +157,15 @@ class App < Sinatra::Application
     def dark_theme?
       app_theme == 'dark'
     end
+
+    def redirect_via_js(path) # courtesy of HTML5 App Cache
+      response.set_cookie :initial_path, value: path, expires: Time.now + 15, path: '/'
+      redirect '/', 302
+    end
+
+    def supports_js_redirection?
+      browser.modern? && !cookies.empty?
+    end
   end
 
   before do
@@ -170,15 +179,19 @@ class App < Sinatra::Application
   end
 
   get '/' do
-    return redirect '/' unless request.query_string.empty?
+    return redirect '/' unless request.query_string.empty? # courtesy of HTML5 App Cache
     erb :index
   end
 
   %w(offline about news help).each do |page|
     get "/#{page}" do
+      if supports_js_redirection?
+        redirect_via_js "/#{page}"
+      else
         redirect "/#/#{page}", 302
       end
     end
+  end
 
   get '/search' do
     redirect "/#q=#{params[:q]}"
@@ -228,8 +241,8 @@ class App < Sinatra::Application
       redirect "/#{doc}#{type}/#{query_string_for_redirection}"
     elsif rest.length > 1 && rest.end_with?('/')
       redirect "/#{doc}#{type}#{rest[0...-1]}#{query_string_for_redirection}"
-    elsif docs.include?(doc) && browser.modern?
+    elsif docs.include?(doc) && supports_js_redirection?
-      redirect "/##{request.path}", 302
+      redirect_via_js(request.path)
     else
       erb :other
     end

test/app_test.rb

@@ -5,6 +5,8 @@ require 'app'
 class AppTest < MiniTest::Spec
   include Rack::Test::Methods
 
+  MODERN_BROWSER = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:39.0) Gecko/20100101 Firefox/39.0'
+
   def app
     App
   end
@@ -40,13 +42,23 @@ class AppTest < MiniTest::Spec
   end
 
   describe "/[static-page]" do
-    it "redirects to /#/[static-page]" do
+    it "redirects to /#/[static-page] by default" do
       %w(offline about news help).each do |page|
-        get "/#{page}"
+        get "/#{page}", {}, 'HTTP_USER_AGENT' => MODERN_BROWSER
         assert last_response.redirect?
         assert_equal "http://example.org/#/#{page}", last_response['Location']
       end
     end
+
+    it "redirects via JS cookie when a cookie exists" do
+      %w(offline about news help).each do |page|
+        set_cookie('foo=bar')
+        get "/#{page}", {}, 'HTTP_USER_AGENT' => MODERN_BROWSER
+        assert last_response.redirect?
+        assert_equal 'http://example.org/', last_response['Location']
+        assert last_response['Set-Cookie'].start_with?("initial_path=%2F#{page}; path=/; expires=")
+      end
+    end
   end
 
   describe "/search" do
@@ -109,15 +121,16 @@ class AppTest < MiniTest::Spec
   describe "/[doc]" do
     it "renders when the doc exists and isn't enabled" do
       set_cookie('docs=css')
-      get '/html/', {}, 'HTTP_USER_AGENT' => 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:39.0) Gecko/20100101 Firefox/39.0'
+      get '/html/', {}, 'HTTP_USER_AGENT' => MODERN_BROWSER
       assert last_response.ok?
     end
 
-    it "redirects to root when the doc exists and is enabled" do
+    it "redirects via JS cookie when the doc exists and is enabled" do
       set_cookie('docs=html')
-      get '/html/', {}, 'HTTP_USER_AGENT' => 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:39.0) Gecko/20100101 Firefox/39.0'
+      get '/html/', {}, 'HTTP_USER_AGENT' => MODERN_BROWSER
       assert last_response.redirect?
-      assert_equal 'http://example.org/#/html/', last_response['Location']
+      assert_equal 'http://example.org/', last_response['Location']
+      assert last_response['Set-Cookie'].start_with?("initial_path=%2Fhtml%2F; path=/; expires=")
     end
 
     it "renders when the doc exists and is enabled, and the request is from Googlebot" do