Check attachment paths for duplicates, not URLs

As per discussion in issue #660, attachments using alias interpolations
for the attachment URL mistakenly get flagged as being duplicates,
although the interpolation expands to a unique location.

This commit (partially) addresses the issue by checking the attachment path
instead. However, the problem will remain for users who use
interpolations other than :class to distinguish attachment paths for
different models.

lib/paperclip.rb

@@ -179,7 +179,7 @@ module Paperclip
 
       attachment_definitions[name] = Paperclip::AttachmentOptions.new(options)
       Paperclip.classes_with_attachments << self.name
-      Paperclip.check_for_url_clash(name,attachment_definitions[name][:url],self.name)
+      Paperclip.check_for_path_clash(name,attachment_definitions[name][:path],self.name)
 
       after_save :save_attached_files
       before_destroy :prepare_for_destroy

lib/paperclip/helpers.rb

@@ -49,13 +49,13 @@ module Paperclip
       end
     end
 
-    def check_for_url_clash(name,url,klass)
-      @names_url ||= {}
-      default_url = url || Attachment.default_options[:url]
-      if @names_url[name] && @names_url[name][:url] == default_url && @names_url[name][:class] != klass && @names_url[name][:url] !~ /:class/
-        log("Duplicate URL for #{name} with #{default_url}. This will clash with attachment defined in #{@names_url[name][:class]} class")
+    def check_for_path_clash(name,path,klass)
+      @names_path ||= {}
+      default_path = path || Attachment.default_options[:path]
+      if @names_path[name] && @names_path[name][:path] == default_path && @names_path[name][:class] != klass && @names_path[name][:path] !~ /:class/
+        log("Duplicate path for #{name} with #{default_path}. This will clash with attachment defined in #{@names_path[name][:class]} class")
       end
-      @names_url[name] = {:url => default_url, :class => klass}
+      @names_path[name] = {:path => default_path, :class => klass}
     end
 
     def reset_duplicate_clash_check!

test/paperclip_test.rb

@@ -114,24 +114,34 @@ class PaperclipTest < Test::Unit::TestCase
       end
     end
 
-    should "generate warning if attachment is redefined with the same url string" do
-      expected_log_msg = "Duplicate URL for blah with /system/:id/:style/:filename. This will clash with attachment defined in Dummy class"
+    should "generate warning if attachment is redefined with the same path string" do
+      expected_log_msg = "Duplicate path for blah with /system/:id/:style/:filename. This will clash with attachment defined in Dummy class"
       Paperclip.expects(:log).with(expected_log_msg)
       Dummy.class_eval do
-        has_attached_file :blah, :url => '/system/:id/:style/:filename'
+        has_attached_file :blah, :path => '/system/:id/:style/:filename'
       end
       Dummy2.class_eval do
-        has_attached_file :blah, :url => '/system/:id/:style/:filename'
+        has_attached_file :blah, :path => '/system/:id/:style/:filename'
       end
     end
 
-    should "not generate warning if attachment is redifined with the same url string but has :class in it" do
+    should "not generate warning if attachment is redefined with the same path string but has :class in it" do
       Paperclip.expects(:log).never
       Dummy.class_eval do
-        has_attached_file :blah, :url => "/system/:class/:attachment/:id/:style/:filename"
+        has_attached_file :blah, :path => "/system/:class/:attachment/:id/:style/:filename"
       end
       Dummy2.class_eval do
-        has_attached_file :blah, :url => "/system/:class/:attachment/:id/:style/:filename"
+        has_attached_file :blah, :path => "/system/:class/:attachment/:id/:style/:filename"
+      end
+    end
+
+    should "not generate warning if attachment is defined with the same URL string" do
+      Paperclip.expects(:log).never
+      Dummy.class_eval do
+        has_attached_file :blah, :path => "/system/:class/:attachment/:id/:style/:filename", :url => ":s3_alias_url"
+      end
+      Dummy2.class_eval do
+        has_attached_file :blah, :path => "/system/:class/:attachment/:id/:style/:filename", :url => ":s3_alias_url"
       end
     end
   end