Lambda (or Proc) support in validation messages

lib/paperclip.rb

@@ -276,6 +276,7 @@ def validates_attachment_size name, options = {}
       max     = options[:less_than]    || (options[:in] && options[:in].last)  || (1.0/0)
       range   = (min..max)
       message = options[:message] || "file size must be between :min and :max bytes."
+      message = message.call if message.respond_to?(:call)
       message = message.gsub(/:min/, min.to_s).gsub(/:max/, max.to_s)
 
       validates_inclusion_of :"#{name}_file_size",
@@ -330,6 +331,7 @@ def validates_attachment_content_type name, options = {}
         if !allowed_types.any?{|t| t === value } && !(value.nil? || value.blank?)
           if record.errors.method(:add).arity == -2
             message = options[:message] || "is not one of #{allowed_types.join(", ")}"
+            message = message.call if message.respond_to?(:call)
             record.errors.add(:"#{name}_content_type", message)
           else
             record.errors.add(:"#{name}_content_type", :inclusion, :default => options[:message], :value => value)

test/paperclip_test.rb

@@ -252,6 +252,21 @@ def self.should_validate validation, options, valid_file, invalid_file
       should_validate validation, options, valid_file, invalid_file
     end
 
+    context "with content_type validation and lambda message" do
+      context "and assigned an invalid file" do
+        setup do
+          Dummy.send(:"validates_attachment_content_type", :avatar, :content_type => %r{image/.*}, :message => lambda {'lambda content type message'})
+          @dummy = Dummy.new
+          @dummy.avatar &&= File.open(File.join(FIXTURES_DIR, "text.txt"), "rb")
+          @dummy.valid?
+        end
+
+        should "have a content type error message" do
+          assert [@dummy.errors[:avatar_content_type]].flatten.any?{|error| error =~ %r/lambda content type message/ }
+        end
+      end
+    end
+
     context "with size validation and less_than 10240 option" do
       context "and assigned an invalid file" do
         setup do
@@ -267,5 +282,20 @@ def self.should_validate validation, options, valid_file, invalid_file
       end
     end
 
+    context "with size validation and less_than 10240 option with lambda message" do
+      context "and assigned an invalid file" do
+        setup do
+          Dummy.send(:"validates_attachment_size", :avatar, :less_than => 10240, :message => lambda {'lambda between 0 and 10240 bytes'})
+          @dummy = Dummy.new
+          @dummy.avatar &&= File.open(File.join(FIXTURES_DIR, "12k.png"), "rb")
+          @dummy.valid?
+        end
+
+        should "have a file size min/max error message" do
+          assert [@dummy.errors[:avatar_file_size]].flatten.any?{|error| error =~ %r/lambda between 0 and 10240 bytes/ }
+        end
+      end
+    end
+
   end
 end