title: Webpacker can't find application
body: <p>I'm creating a new rails application according to "Getting Started with Rails". The application starts normally in step 4.1. But when i create my first controller, i have a webpack error.</p>
  
  <p>I'm new in webpack, i have red all documentation, but i don't understand what is wrong or missing...</p>
  
  <ul>
  <li>Windows 10 1903</li>
  <li>ruby 2.6 </li>
  <li>rails 6.0.0</li>
  <li>nodeJS 12.11.0</li>
  </ul>
  
  <hr>
  
  <pre><code>rails webpacker:install
     identical  config/webpacker.yml
  Copying webpack core config
         exist  config/webpack
     identical  config/webpack/development.js
     identical  config/webpack/environment.js
     identical  config/webpack/production.js
     identical  config/webpack/test.js
  Copying postcss.config.js to app root directory
     identical  postcss.config.js
  Copying babel.config.js to app root directory
     identical  babel.config.js
  Copying .browserslistrc to app root directory
     identical  .browserslistrc
  The JavaScript app source directory already exists
         apply  C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/webpacker-4.0.7/lib/install/binstubs.rb
    Copying binstubs
         exist    bin
     identical    bin/webpack
     identical    bin/webpack-dev-server
        append  .gitignore
  Installing all JavaScript dependencies [4.0.7]
           run  yarn add @rails/webpacker from "."
  yarn add v1.17.3
  [1/4] Resolving packages...
  [2/4] Fetching packages...
  info fsevents@1.2.9: The platform "win32" is incompatible with this module.
  info "fsevents@1.2.9" is an optional dependency and failed compatibility check. Excluding it from installation.
  [3/4] Linking dependencies...
  warning " &gt; webpack-dev-server@3.8.2" has unmet peer dependency "webpack@^4.0.0".
  warning "webpack-dev-server &gt; webpack-dev-middleware@3.7.2" has unmet peer dependency "webpack@^4.0.0".
  [4/4] Building fresh packages...
  success Saved 1 new dependency.
  info Direct dependencies
  └─ @rails/webpacker@4.0.7
  info All dependencies
  └─ @rails/webpacker@4.0.7
  Done in 4.48s.
  Installing dev server for live reloading
           run  yarn add --dev webpack-dev-server from "."
  yarn add v1.17.3
  [1/4] Resolving packages...
  [2/4] Fetching packages...
  info fsevents@1.2.9: The platform "win32" is incompatible with this module.
  info "fsevents@1.2.9" is an optional dependency and failed compatibility check. Excluding it from installation.
  [3/4] Linking dependencies...
  warning "webpack-dev-server &gt; webpack-dev-middleware@3.7.2" has unmet peer dependency "webpack@^4.0.0".
  warning " &gt; webpack-dev-server@3.8.2" has unmet peer dependency "webpack@^4.0.0".
  [4/4] Building fresh packages...
  success Saved 1 new dependency.
  info Direct dependencies
  └─ webpack-dev-server@3.8.2
  info All dependencies
  └─ webpack-dev-server@3.8.2
  Done in 4.92s.
  Webpacker successfully installed �
  </code></pre>
  
  <hr>
  
  <pre><code>Webpacker::Manifest::MissingEntryError in Welcome#index
  
  Showing C:/Users/[...]/site_test/app/views/layouts/application.html.erb where line #9 raised:
  
  Webpacker can't find application in C:/Users/[...]/site_test/public/packs/manifest.json. Possible causes:
  1. You want to set webpacker.yml value of compile to true for your environment
     unless you are using the `webpack -w` or the webpack-dev-server.
  2. webpack has not yet re-run to reflect updates.
  3. You have misconfigured Webpacker's config/webpacker.yml file.
  4. Your webpack configuration is not creating a manifest.
  Your manifest contains:
  {
  }
  
  Extracted source (around line #9):
  
  7
  8      &lt;%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %&gt;
  9      &lt;%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %&gt;
  10 &lt;/head&gt;
  11 &lt;body&gt;
  12
  </code></pre>