Use date comparison instead of string comparison for last_modified helper. Fixes #98.

lib/sinatra/base.rb

@@ -312,13 +312,9 @@ module Sinatra
       return unless time
       time = time.to_time if time.respond_to?(:to_time)
       time = Time.parse time.strftime('%FT%T%:z') if time.respond_to?(:strftime)
-      time = time.httpdate if time.respond_to?(:httpdate)
+      response['Last-Modified'] = time.respond_to?(:httpdate) ? time.httpdate : time.to_s
-      response['Last-Modified'] = time.to_s
+      halt 304 if Time.httpdate(request.env['HTTP_IF_MODIFIED_SINCE']) >= time
-      begin
+    rescue ArgumentError
-        halt 304 if time <= Time.httpdate(request.env['HTTP_IF_MODIFIED_SINCE']).httpdate
-      rescue ArgumentError
-      end
-      time
     end
 
     # Set the response entity tag (HTTP 'ETag' header) and halt if conditional

test/helpers_test.rb

@@ -522,6 +522,19 @@ class HelpersTest < Test::Unit::TestCase
             assert_equal 200, status
             assert_equal 'Boo!', body
           end
+
+          it 'does not rely on string comparison' do
+            mock_app do
+              get '/compare' do
+                last_modified "Mon, 18 Oct 2010 20:57:11 GMT"
+                "foo"
+              end
+            end
+
+            get '/compare', {}, { 'HTTP_IF_MODIFIED_SINCE' => 'Sun, 26 Sep 2010 23:43:52 GMT' }
+            assert_equal 200, status
+            assert_equal 'foo', body
+          end
         end
 
         context "when the resource has been modified on the exact If-Modified-Since header date" do