Fix s3 writes with style procs

S3#flush_writes was accessing the styles option without checking for a
proc. We can just use the instance's styles method to have it done for
us.

lib/paperclip/storage/s3.rb

@@ -310,7 +310,7 @@ module Paperclip
               write_options[:server_side_encryption] = @s3_server_side_encryption
               write_options[:server_side_encryption] = @s3_server_side_encryption
             end
             end
 
 
-            style_specific_options = @options[:styles][style]
+            style_specific_options = styles[style]
             if style_specific_options.is_a?(Hash)
             if style_specific_options.is_a?(Hash)
               merge_s3_headers( style_specific_options[:s3_headers], @s3_headers, @s3_metadata) if style_specific_options.has_key?(:s3_headers)
               merge_s3_headers( style_specific_options[:s3_headers], @s3_headers, @s3_metadata) if style_specific_options.has_key?(:s3_headers)
               @s3_metadata.merge!(style_specific_options[:s3_metadata]) if style_specific_options.has_key?(:s3_metadata)
               @s3_metadata.merge!(style_specific_options[:s3_metadata]) if style_specific_options.has_key?(:s3_metadata)

test/storage/s3_test.rb

@@ -292,6 +292,43 @@ class S3Test < Test::Unit::TestCase
     end
     end
   end
   end
 
 
+  context "An attachment that uses S3 for storage and has a proc for styles" do
+    setup do
+      rebuild_model :styles  => lambda { |attachment| attachment.instance.counter; {:thumbnail => '20x20#'} },
+                    :storage => :s3,
+                    :bucket  => "bucket",
+                    :path => ":attachment/:style/:basename.:extension",
+                    :s3_credentials => {
+                      'access_key_id' => "12345",
+                      'secret_access_key' => "54321"
+                    }
+
+      @file = File.new(fixture_file('5k.png'), 'rb')
+
+      Dummy.class_eval do
+        def counter
+          @counter ||= 0
+          @counter += 1
+          @counter
+        end
+      end
+
+      @dummy = Dummy.new
+      @dummy.avatar = @file
+
+      object = stub
+      @dummy.avatar.stubs(:s3_object).returns(object)
+      object.expects(:write).with(anything, anything).twice
+      @dummy.save
+    end
+
+    teardown { @file.close }
+
+    should "succeed" do
+      assert_equal @dummy.counter, 7
+    end
+  end
+
   context "An attachment that uses S3 for storage and has spaces in file name" do
   context "An attachment that uses S3 for storage and has spaces in file name" do
     setup do
     setup do
       rebuild_model :styles  => { :large => ['500x500#', :jpg] },
       rebuild_model :styles  => { :large => ['500x500#', :jpg] },