500: TypeError (no implicit conversion of nil into String)

[jgrannas]

I cannot figure out what is causing this TypeError. I have another rails app on Rails 4.0.3 where it works, and this Rails 4.1.5 app does not work.

class ImagesController < ApplicationController
  load_and_authorize_resource

  before_action :set_image, only: [:destroy]

  def create

    p_attr = params[:image]
    p_attr[:gallery_id] = params[:image][:gallery_id]
    p_attr[:file] = params[:image][:file].first if params[:image][:file].class == Array

    @image = Image.new(p_attr)
    if @image.save
      respond_to do |format|
        format.js
        format.html {  
          render :json => [@image.to_jq_upload].to_json, 
          :content_type => 'text/html',
          :layout => false
        }
        format.json {  
          render :json => { :files => [@image.to_jq_upload] }     
        }
      end
    else 
      render :json => [{:error => "custom_failure"}], :status => 304
    end

  end

  def destroy
    @image.destroy
    render :json => true
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_image
      @image = Image.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def image_params
      params.require(:image).permit(:gallery_id, file:[])
    end

end

Started POST "/images" for 127.0.0.1 at 2014-10-02 13:48:39 -0400
Processing by ImagesController#create as JSON
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"6pvN7Ssl0Epye/CaUXKuakDItf1MkJi3KGA200Kwgvs=", "image"=>{"gallery_id"=>"3", "file"=>[#<ActionDispatch::Http::UploadedFile:0x007ff23c3d0730 @tempfile=#<Tempfile:/var/folders/3m/t1v11gzj32n0fdbhwr823y600000gn/T/RackMultipart20141002-38945-pt6cs6>, @original_filename="P7310618.JPG", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"image[file][]\"; filename=\"P7310618.JPG\"\r\nContent-Type: image/jpeg\r\n">]}}
Completed 500 Internal Server Error in 24ms

TypeError (no implicit conversion of nil into String):
  carrierwave (0.10.0) lib/carrierwave/uploader/cache.rb:159:in `join'
  carrierwave (0.10.0) lib/carrierwave/uploader/cache.rb:159:in `cache_path'
  carrierwave (0.10.0) lib/carrierwave/uploader/cache.rb:131:in `block in cache!'
  carrierwave (0.10.0) lib/carrierwave/uploader/callbacks.rb:17:in `with_callbacks'
  carrierwave (0.10.0) lib/carrierwave/uploader/cache.rb:122:in `cache!'
  carrierwave (0.10.0) lib/carrierwave/mount.rb:329:in `cache'
  carrierwave (0.10.0) lib/carrierwave/mount.rb:163:in `file='
  carrierwave (0.10.0) lib/carrierwave/orm/activerecord.rb:39:in `file='
  activerecord (4.1.5) lib/active_record/attribute_assignment.rb:45:in `public_send'
  activerecord (4.1.5) lib/active_record/attribute_assignment.rb:45:in `_assign_attribute'
  activerecord (4.1.5) lib/active_record/attribute_assignment.rb:32:in `block in assign_attributes'
  activerecord (4.1.5) lib/active_record/attribute_assignment.rb:26:in `each'
  activerecord (4.1.5) lib/active_record/attribute_assignment.rb:26:in `assign_attributes'
  activerecord (4.1.5) lib/active_record/core.rb:455:in `init_attributes'
  activerecord (4.1.5) lib/active_record/core.rb:198:in `initialize'
  actionpack (4.1.5) lib/action_dispatch/routing/url_for.rb:104:in `initialize'
  activerecord (4.1.5) lib/active_record/inheritance.rb:30:in `new'
  activerecord (4.1.5) lib/active_record/inheritance.rb:30:in `new'
  cancancan (1.9.2) lib/cancan/controller_resource.rb:85:in `build_resource'
  cancancan (1.9.2) lib/cancan/controller_resource.rb:66:in `load_resource_instance'
  cancancan (1.9.2) lib/cancan/controller_resource.rb:32:in `load_resource'
  cancancan (1.9.2) lib/cancan/controller_resource.rb:25:in `load_and_authorize_resource'
  cancancan (1.9.2) lib/cancan/controller_resource.rb:10:in `block in add_before_filter'
  activesupport (4.1.5) lib/active_support/callbacks.rb:440:in `instance_exec'
  activesupport (4.1.5) lib/active_support/callbacks.rb:440:in `block in make_lambda'
  activesupport (4.1.5) lib/active_support/callbacks.rb:160:in `call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:160:in `block in halting'
  activesupport (4.1.5) lib/active_support/callbacks.rb:229:in `call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:229:in `block in halting'
  activesupport (4.1.5) lib/active_support/callbacks.rb:229:in `call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:229:in `block in halting'
  activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.5) lib/active_support/callbacks.rb:86:in `call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:86:in `run_callbacks'
  actionpack (4.1.5) lib/abstract_controller/callbacks.rb:19:in `process_action'
  actionpack (4.1.5) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (4.1.5) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
  activesupport (4.1.5) lib/active_support/notifications.rb:159:in `block in instrument'
  activesupport (4.1.5) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.1.5) lib/active_support/notifications.rb:159:in `instrument'
  actionpack (4.1.5) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  actionpack (4.1.5) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  activerecord (4.1.5) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  actionpack (4.1.5) lib/abstract_controller/base.rb:136:in `process'
  actionview (4.1.5) lib/action_view/rendering.rb:30:in `process'
  actionpack (4.1.5) lib/action_controller/metal.rb:196:in `dispatch'
  actionpack (4.1.5) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  actionpack (4.1.5) lib/action_controller/metal.rb:232:in `block in action'
  actionpack (4.1.5) lib/action_dispatch/routing/route_set.rb:82:in `call'
  actionpack (4.1.5) lib/action_dispatch/routing/route_set.rb:82:in `dispatch'
  actionpack (4.1.5) lib/action_dispatch/routing/route_set.rb:50:in `call'
  actionpack (4.1.5) lib/action_dispatch/journey/router.rb:71:in `block in call'
  actionpack (4.1.5) lib/action_dispatch/journey/router.rb:59:in `each'
  actionpack (4.1.5) lib/action_dispatch/journey/router.rb:59:in `call'
  actionpack (4.1.5) lib/action_dispatch/routing/route_set.rb:678:in `call'
  jquery-fileupload-rails (0.4.1) lib/jquery/fileupload/rails/middleware.rb:14:in `_call'
  jquery-fileupload-rails (0.4.1) lib/jquery/fileupload/rails/middleware.rb:10:in `call'
  warden (1.2.3) lib/warden/manager.rb:35:in `block in call'
  warden (1.2.3) lib/warden/manager.rb:34:in `catch'
  warden (1.2.3) lib/warden/manager.rb:34:in `call'
  rack (1.5.2) lib/rack/etag.rb:23:in `call'
  rack (1.5.2) lib/rack/conditionalget.rb:35:in `call'
  rack (1.5.2) lib/rack/head.rb:11:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/flash.rb:254:in `call'
  rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
  rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/cookies.rb:560:in `call'
  activerecord (4.1.5) lib/active_record/query_cache.rb:36:in `call'
  activerecord (4.1.5) lib/active_record/connection_adapters/abstract/connection_pool.rb:621:in `call'
  activerecord (4.1.5) lib/active_record/migration.rb:380:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.1.5) lib/active_support/callbacks.rb:82:in `run_callbacks'
  actionpack (4.1.5) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/reloader.rb:73:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.1.5) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.1.5) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.1.5) lib/active_support/tagged_logging.rb:68:in `block in tagged'
  activesupport (4.1.5) lib/active_support/tagged_logging.rb:26:in `tagged'
  activesupport (4.1.5) lib/active_support/tagged_logging.rb:68:in `tagged'
  railties (4.1.5) lib/rails/rack/logger.rb:20:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
  rack (1.5.2) lib/rack/runtime.rb:17:in `call'
  activesupport (4.1.5) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  actionpack (4.1.5) lib/action_dispatch/middleware/static.rb:64:in `call'
  rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
  railties (4.1.5) lib/rails/engine.rb:514:in `call'
  railties (4.1.5) lib/rails/application.rb:144:in `call'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:155:in `handle'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:109:in `rescue in block (2 levels) in start'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:106:in `block (2 levels) in start'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:96:in `each'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:96:in `block in start'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:76:in `loop'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:76:in `start'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/lib/nack/server.rb:12:in `run'
  /Users/joel/Library/Application Support/Pow/Versions/0.4.3/node_modules/nack/bin/nack_worker:4:in `<main>'

  Rendered /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.1.5/lib/action_dispatch/middleware/templates/rescues/_source.erb (0.5ms)
  Rendered /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.1.5/lib/action_dispatch/middleware/templates/rescues/_trace.text.erb (0.5ms)
  Rendered /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.1.5/lib/action_dispatch/middleware/templates/rescues/_request_and_response.text.erb (0.7ms)
  Rendered /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.1.5/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb (13.5ms)

[felixbuenemann]

Not a bug, exception happens in carrierwave. My guess wrong params hash or form encoding (should be multipart when using form upload).