title: NoMethodError: undefined method `+' for nil:NilClass / 'additional_paths' [capistrano+webpacker]
body: <p>I had to update my rails version from 5 to 6, before that everything was working just fine.</p>
  
  <p>the problem only happens with capistrano... when I run <code>rake assets:precompile</code> everything works as well even with the new version.</p>
  
  <p>this is the error:</p>
  
  <pre class="lang-sh prettyprint-override"><code>deploy:assets:precompile
        01 $HOME/.rbenv/bin/rbenv exec bundle exec rake assets:precompile
        01 warning: parser/current is loading parser/ruby25, which recognizes
        01 warning: 2.5.7-compliant syntax, but you are running 2.5.3.
        01 warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
  
  yarn install v1.16.0
  [1/4] Resolving packages...
  ⠁
  
  success Already up-to-date.
  Done in 0.71s.
        01 Warning: you are using an unstable release of Node.js (v11.15.0). If you encounter issues with Node.js, consider switching to an Active LTS release. More info: https://docs.npmjs.com/try-the-latest-stable-version-of-node
        01 Webpacker::Compiler.watched_paths has been deprecated. Set additional_paths in webpacker.yml instead.
        01 rake aborted!
        01 NoMethodError: undefined method `+' for nil:NilClass
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/configuration.rb:31:in `additional_paths'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/configuration.rb:35:in `additional_paths_globbed'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/compiler.rb:93:in `default_watched_paths'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/compiler.rb:57:in `watched_files_digest'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/compiler.rb:38:in `fresh?'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/compiler.rb:43:in `stale?'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/compiler.rb:22:in `compile'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker/commands.rb:51:in `compile'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker.rb:35:in `compile'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/tasks/webpacker/compile.rake:23:in `block (4 levels) in &lt;top (required)&gt;'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker.rb:28:in `ensure_log_goes_to_stdout'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/tasks/webpacker/compile.rake:22:in `block (3 levels) in &lt;top (required)&gt;'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/webpacker.rb:20:in `with_node_env'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/tasks/webpacker/compile.rake:21:in `block (2 levels) in &lt;top (required)&gt;'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/bundler/gems/webpacker-d099e066931b/lib/tasks/webpacker/compile.rake:14:in `block in enhance_assets_precompile'
        01 /web/export-at-ibm/shared/bundle/ruby/2.5.0/gems/rake-12.3.3/exe/rake:27:in `&lt;top (required)&gt;'
        01 /home/glbrgit/.rbenv/versions/2.5.3/bin/bundle:23:in `load'
        01 /home/glbrgit/.rbenv/versions/2.5.3/bin/bundle:23:in `&lt;main&gt;'
        01 Tasks: TOP =&gt; webpacker:compile
        01 (See full trace by running task with --trace)
  #&lt;Thread:0x00007fec80b805a0@/Users/thiagogs/.rvm/gems/ruby-2.5.3/gems/sshkit-1.21.0/lib/sshkit/runners/parallel.rb:10 run&gt; terminated with exception (report_on_exception is true):
  Traceback (most recent call last):
      1: from /Users/thiagogs/.rvm/gems/ruby-2.5.3/gems/sshkit-1.21.0/lib/sshkit/runners/parallel.rb:11:in `block (2 levels) in execute'
  /Users/thiagogs/.rvm/gems/ruby-2.5.3/gems/sshkit-1.21.0/lib/sshkit/runners/parallel.rb:15:in `rescue in block (2 levels) in execute': Exception while executing as glbrgit@test-export.w3-969.ibm.com: rake exit status: 1 (SSHKit::Runner::ExecuteError)
  rake stdout: warning: parser/current is loading parser/ruby25, which recognizes
  warning: 2.5.7-compliant syntax, but you are running 2.5.3.
  warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
  yarn install v1.16.0
  [1/4] Resolving packages...
  success Already up-to-date.
  Done in 0.71s.
  </code></pre>
  
  <p>these are my files:</p>
  
  <p><strong>config/application.rb</strong></p>
  
  <pre class="lang-rb prettyprint-override"><code>require 'rails'
  # Pick the frameworks you want:
  require 'active_model/railtie'
  require 'active_job/railtie'
  # require "active_record/railtie"
  # require "active_storage/engine"
  require 'action_controller/railtie'
  require 'action_mailer/railtie'
  require 'action_view/railtie'
  require 'action_cable/engine'
  require 'sprockets/railtie'
  # require "rails/test_unit/railtie"
  require 'i18n/backend/fallbacks'
  
  # Require the gems listed in Gemfile, including any gems
  # you've limited to :test, :development, or :production.
  Bundler.require(*Rails.groups)
  
  # Webpacker::Compiler.watched_paths &lt;&lt; '../app/javascript'
  I18n::Backend::Simple.send(:include, I18n::Backend::Fallbacks)
  
  module ExportAtIbm
      class Application &lt; Rails::Application
          I18n.available_locales = %w[en br]
          config.i18n.default_locale = :br
          config.i18n.fallbacks = [I18n.default_locale]
  
          config.middleware.use I18n::JS::Middleware
  
          # Initialize configuration defaults for originally generated Rails version.
          config.load_defaults 5.2
  
          config.autoload_paths &lt;&lt; "#{Rails.root}/lib"
          config.eager_load_paths &lt;&lt; "#{Rails.root}/lib"
  
          config.assets.paths &lt;&lt; Rails.root.join('app', 'assets', 'font', 'roboto')
          config.assets.paths &lt;&lt; Rails.root.join('vendor', 'assets', 'img')
          config.assets.paths &lt;&lt; Rails.root.join('vendor', 'assets', 'mdb-addons')
  
          config.generators do |generator|
              generator.stylesheets = false
              generator.javascripts = false
              generator.helper = false
  
              generator.fixture_replacement :factory_bot, dir: 'spec/support/factory_bot/'
          end
  
          # Settings in config/environments/* take precedence over those specified here.
          # Application configuration should go into files in config/initializers
          # -- all .rb files in that directory are automatically loaded.
          Apipie.configure do |config|
              config.validate = false
          end
  
          config.assets.precompile &lt;&lt; %w[i18n i18n/*]
  
          # Don't generate system test files.
          config.generators.system_tests = nil
          config.customs = {
              integrations: JSON.parse(config_for(:integrations).to_json, symbolize_names: true)
          }
      end
  end
  </code></pre>
  
  <p><strong>config/deploy.rb</strong></p>
  
  <pre class="lang-rb prettyprint-override"><code># Server info
  server 'test-export.w3-969.ibm.com', user: 'glbrgit', roles: %w[app worker], primary: true
  
  # General configs
  set :ssh_options,     forward_agent: true, user: 'glbrgit', keys: %w[~/.ssh/id_rsa.pub]
  set :pty,             true
  set :use_sudo,        false
  set :stage,           :staging
  set :deploy_via,      :remote_cache
  set :deploy_to,       '/web/export-at-ibm'
  set :rbenv_ruby,      '2.5.3'
  set :branch,          'test-qa'
  set :linked_files,    %w[config/master.key]
  set :linked_dirs,     %w[assets/uploads]
  append :rbenv_map_bins, 'puma', 'pumactl'
  
  # Puma configs
  set :puma_threads, [4, 16]
  set :puma_workers, 6
  set :puma_bind,       'tcp://0.0.0.0:3007'
  set :puma_state,      "#{shared_path}/tmp/pids/puma.state"
  set :puma_pid,        "#{shared_path}/tmp/pids/puma.pid"
  set :puma_access_log, "#{release_path}/log/puma.access.log"
  set :puma_error_log,  "#{release_path}/log/puma.error.log"
  set :puma_worker_timeout, nil
  set :puma_init_active_record, false # Change to false when not using ActiveRecord
  
  # Create puma directories
  namespace :puma do
      desc 'Pre-config and Create Directories for Puma Pids and Socket'
      task :make_dirs do
          on roles(:app) do
              execute "mkdir #{shared_path}/tmp/sockets -p"
              execute "mkdir #{shared_path}/tmp/pids -p"
          end
      end
  
      before :start, :make_dirs
  end
  
  # Deploys tasks
  namespace :deploy do
      desc 'Make sure local git is in sync with remote.'
      task :check_revision do
          on roles(:app) do
              unless `git rev-parse HEAD` == `git rev-parse origin/test-qa`
                  puts 'WARNING: HEAD is not the same as origin/test-qa'
                  puts 'Run `git push` to sync changes.'
                  exit
              end
          end
      end
  
      desc 'Initial Deploy'
      task :initial do
          on roles(:app) do
              before 'deploy:restart', 'puma:start'
              invoke 'deploy'
          end
      end
  
      desc 'Compile static dependencies'
      task :compile_assets do
          on roles(:app) do
              execute "cd #{release_path}/ &amp;&amp; RAILS_ENV=staging ~/.rbenv/shims/bundle exec rake assets:svg"
          end
      end
  
      desc 'Run rake yarn:install'
      task :yarn_install do
          on roles(:app) do
              execute "cd #{release_path} &amp;&amp; yarn install --force"
          end
      end
  
      desc 'Run rake i18n_js_export'
      task :i18n_js_export do
          on roles(:app) do
              execute "cd #{release_path}/ &amp;&amp; RAILS_ENV=staging ~/.rbenv/shims/bundle exec rake i18n:js:export"
          end
      end
  
      before 'compile_assets', 'deploy:i18n_js_export'
      before 'compile_assets', 'deploy:yarn_install'
      after :finishing, :compile_assets
      after :finishing, 'deploy:cleanup'
      after :finishing, :restart
  end
  
  </code></pre>
  
  <p><strong>config/webpacker.yml</strong></p>
  
  <pre class="lang-yaml prettyprint-override"><code># Note: You must restart bin/webpack-dev-server for changes to take effect
  
  default: &amp;default
    source_path: app/javascript
    source_entry_path: .
    public_root_path: public
    public_output_path: packs
    cache_path: tmp/cache/webpacker
    check_yarn_integrity: false
    compile: true
  
    # Additional paths webpack should lookup modules
    # ['app/assets', 'engine/foo/app/assets']
    resolved_paths: []
  
    additional_paths:
      - /app/javascript
  
    # Reload manifest.json on all requests so we reload latest compiled packs
    cache_manifest: false
  
    # Extract and emit a css file
    extract_css: true
  
    static_assets_extensions:
      - .jpg
      - .jpeg
      - .png
      - .gif
      - .tiff
      - .ico
      - .svg
      - .eot
      - .otf
      - .ttf
      - .woff
      - .woff2
  
    extensions:
      - .vue
      - .mjs
      - .js
      - .sass
      - .scss
      - .css
      - .module.sass
      - .module.scss
      - .module.css
      - .png
      - .svg
      - .gif
      - .jpeg
      - .jpg
      - .vue
  
  development:
    &lt;&lt;: *default
  
    # Verifies that versions and hashed value of the package contents in the project's package.json
    check_yarn_integrity: true
    webpack_compile_output: true
  
    # Reference: https://webpack.js.org/configuration/dev-server/
    dev_server:
      https: false
      host: localhost
      port: 3035
      public: localhost:3035
      hmr: false
      # Inline should be set to true if using HMR
      inline: true
      overlay: true
      compress: true
      disable_host_check: true
      use_local_ip: false
      quiet: false
      headers:
        'Access-Control-Allow-Origin': '*'
      watch_options:
        ignored: '**/node_modules/**'
      mode: development
  
  test:
    &lt;&lt;: *default
    compile: false
    cache_manifest: true
  
    # Compile test packs to a separate directory
    public_output_path: packs-test
  
  staging:
    &lt;&lt;: *default
  
    # Production depends on precompilation of packs prior to booting for performance.
    compile: false
  
    # Extract and emit a css file
    extract_css: true
  
    # Cache manifest.json for performance
    cache_manifest: false
  
  production:
    &lt;&lt;: *default
  
    # Production depends on precompilation of packs prior to booting for performance.
    compile: false
  
    # Extract and emit a css file
    extract_css: true
  
    # Cache manifest.json for performance
    cache_manifest: false
  
  </code></pre>
  
  <p>can anyone help me out on this?</p>