Extra checking on the content type detector

lib/paperclip/content_type_detector.rb

 module Paperclip
   class ContentTypeDetector
+    EMPTY_TYPE = "inode/x-empty"
+    SENSIBLE_DEFAULT = "application/octet-stream"
+
     def initialize(filename)
       @filename = filename
     end
 
     def detect
-      if !match?
+      if blank?
+        SENSIBLE_DEFAULT
+      elsif empty?
+        EMPTY_TYPE
+      elsif !match?
         type_from_file_command
       elsif !multiple?
         possible_types.first
@@ -16,6 +23,14 @@ module Paperclip
 
     private
 
+    def empty?
+      File.exists?(@filename) && File.size(@filename) == 0
+    end
+
+    def blank?
+      @filename.nil? || @filename.empty?
+    end
+
     def possible_types
       @possible_types ||= MIME::Types.type_for(@filename)
     end
@@ -37,7 +52,7 @@ module Paperclip
       # On BSDs, `file` doesn't give a result code of 1 if the file doesn't exist.
       type = Paperclip.run("file", "-b --mime :file", :file => @filename)
       if type.match(/\(.*?\)/)
-        type = "application/octet-stream"
+        type = SENSIBLE_DEFAULT
       end
       type.split(/[:;\s]+/)[0]
     end

test/content_type_detector_test.rb

@@ -15,6 +15,17 @@ class ContentTypeDetectorTest < Test::Unit::TestCase
       assert_equal "text/plain", Paperclip::ContentTypeDetector.new(tempfile.path).detect
     end
 
+    should 'return an empty content type if the file is empty' do
+      tempfile = Tempfile.new("something")
+      tempfile.rewind
+
+      assert_equal "inode/x-empty", Paperclip::ContentTypeDetector.new(tempfile.path).detect
+    end
+
+    should 'return a sensible default if no filename is supplied' do
+      assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new('').detect
+    end
+
     should 'return a sensible default if something goes wrong' do
       @filename = "/path/to/something"
       assert_equal "application/octet-stream", Paperclip::ContentTypeDetector.new(@filename).detect

test/io_adapters/abstract_adapter_test.rb

@@ -5,15 +5,14 @@ class AbstractAdapterTest < Test::Unit::TestCase
     attr_accessor :original_file_name, :tempfile
 
     def content_type
-      type_from_file_command
+      Paperclip::ContentTypeDetector.new(path).detect
     end
   end
 
   context "content type from file command" do
     setup do
       @adapter = TestAdapter.new
-      @adapter.stubs(:path)
-      Paperclip.stubs(:run).returns("image/png\n")
+      @adapter.stubs(:path).returns("image.png")
     end
 
     should "return the content type without newline" do