paperclip validations causing Error in Rails 3

I've recently installed the paperclip gem to my Rails 3 app. I am trying to allow users to upload an avatar to their profile. I followed the install instructions and here is what my models/views look like:

My 'user.rb' model has the following code:

has_attached_file :avatar, 
                  :styles => { :small => "70x70>"},
                  :url  => "/users/:attachment/:id/:style/:basename.:extension",
                  :path => ":rails_root/public/users/:attachment/:id/:style/:basename.:extension"

validates_attachment_size :avatar, :less_than => 1.megabytes
validates_attachment_content_type :avatar, :content_type => ['image/jpeg', 'image/png']

I have added the following to the edit form html (I'm using HAML btw):

= form_for (@user || User.new), :html => { :multipart => true } do |f|
...
.profile_picture.text_field
  = image_tag current_profile.avatar.url(:small)
  %br
  = f.file_field :avatar

When I upload a picture (jpeg or png) that is under 1mb everything works smoothly; the image is uploaded, and there are no errors. If I try to upload any other type of file (MP3, txt, whatever) or the file/image is greater than 1mb rails gives me the following error:

TypeError in UsersController#update

can't dump File

Request

Parameters:

{"utf8"=>"✓",
 "_method"=>"put",
 "authenticity_token"=>"LaiYjEEfgsE8JzzLsfkzk6TK8D4uxzIo5ASlu6ax2rY=",
 "user"=>{"avatar"=>#<ActionDispatch::Http::UploadedFile:0x000001053f0bf0 @original_filename="GT1_22HS_1_std.jpg",
 @content_type="image/jpeg",
 @headers="Content-Disposition: form-data; name=\"user[avatar]\"; filename=\"GT1_22HS_1_std.jpg\"\r\nContent-Type: image/jpeg\r\n",
 @tempfile=#<File:/var/folders/Ud/Udv4OlryEzWrHedR8pIe1E+++TI/-Tmp-/RackMultipart20110817-17075-1ikqcc0>>,
 "first_name"=>"First",
 "last_name"=>"Last",
 "country"=>"United States",
 "state"=>"California",
 "city"=>"City",
 "date_of_birth(1i)"=>"2011",
 "date_of_birth(2开发者_高级运维i)"=>"7",
 "date_of_birth(3i)"=>"12",
 "account_attributes"=>{"email"=>"email@email.com",
 "id"=>"6",
 "password"=>"[FILTERED]",
 "password_confirmation"=>"[FILTERED]"},
 "commit"=>"Save & Continue",
 "id"=>"2"}

I apologize if all of that was not required, but the error is a little non-descriptive, so I figured it's better to post in just in case.

I would like to know what I'm doing wrong with my validations that errors are not being generated, and the application is breaking. Any help on this matter would be greatly appreciated. I sincerely thank everyone who took the time to read this, and I kindly appreciate any help! Thanks!

UPDATE:

update method form user_controller.rb:

  def update
    session[:user_params] ||= {}
    session[:user_params].deep_merge!(params[:user]) if params[:user].present?

    @user.attributes = session[:user_params]

    respond_to do |format|
      if @user.save
        session[:user_params] = nil
        sign_in(@user.account, :bypass => true)
        format.html { redirect_to(root_url, :notice => 'User was successfully updated.') }
        format.xml  { render :xml => @user, :status => :created, :location => @user }
      else
        format.html { render :action => "edit", :layout => "userhome" }
        format.xml  { render :xml => @user.errors, :status => :unprocessable_entity }
      end
    end
  end

can't dump File is the error Ruby raises when it is asked to dump a File object using Marshal.dump.

Marshal.dump(File.new(".gemrc")) # => TypeError: can't dump File

So the problem lies probably in what you do when the validation fails. If you're putting the params (which contains a File object) in the session or the flash objects (which are dumped by Rails), this is your problem.

The problem in my case that clearing out the paperclip attachment with Attachment#clear was not enough because it still wanted to save some File.

I've found out that the problem was with the @queued_for_write attribute in Attachment which still contained the data.

So the following two lines solved my problem:

unless @model.valid?
  @model.image.clear
  @model.image.queued_for_write.clear
end

This was a paperclip bug and was corrected in this commit.

Did you try

@user.attachment.destroy

before assigning @user.errors in your response?