title: Webpack error on Heroku Deployment
body: <p>Running my rails app locally works fine. Then I deployed it to Heroku successfully but when opening the app I get the error: </p>
  
  <p><em>"We're sorry, but something went wrong.
  If you are the application owner check the logs for more information."</em></p>
  
  <p>I'm new to using Heroku, this is my first deployed app so not completely sure of how everything works. In my heroku logs it says that:</p>
  
  <blockquote>
    <p>ActionView::Template::Error (Webpacker can't find application.css in
    /app/public/packs/manifest.json. Possible causes:</p>
    
    <ol>
    <li>You want to set webpacker.yml value of compile to true for your environment</li>
    <li>Webpack has not yet re-run to reflect updates.</li>
    <li>You have misconfigured Webpacker's config/webpacker.yml file. unless you are using the <code>webpack -w</code> or the webpack-dev-server.</li>
    <li>Your Webpack configuration is not creating a manifest.</li>
    </ol>
  </blockquote>
  
  <p>Anyone that has had the same problem or has any tips on how to try and solve this? </p>
  
  <hr>
  
  <p><strong>This is the whole heroku log:</strong></p>
  
  <pre><code>2017-11-19T12:30:56.336758+00:00 app[web.1]: I, [2017-11-19T12:30:56.336675 #4]  INFO -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c] Started GET "/" for 85.228.31.12 at 2017-11-19 12:30:56 +0000
  2017-11-19T12:30:56.338912+00:00 app[web.1]: I, [2017-11-19T12:30:56.338848 #4]  INFO -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]   Rendered react_view/index.html.erb within layouts/application (0.7ms)
  2017-11-19T12:30:56.337434+00:00 app[web.1]: I, [2017-11-19T12:30:56.337362 #4]  INFO -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c] Processing by ReactViewController#index as HTML
  2017-11-19T12:30:56.338062+00:00 app[web.1]: I, [2017-11-19T12:30:56.337995 #4]  INFO -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]   Rendering react_view/index.html.erb within layouts/application
  2017-11-19T12:30:56.339074+00:00 app[web.1]: I, [2017-11-19T12:30:56.339014 #4]  INFO -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c] Completed 500 Internal Server Error in 2ms
  2017-11-19T12:30:56.339692+00:00 app[web.1]: F, [2017-11-19T12:30:56.339632 #4] FATAL -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]   
  2017-11-19T12:30:56.339766+00:00 app[web.1]: F, [2017-11-19T12:30:56.339696 #4] FATAL -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c] ActionView::Template::Error (Webpacker can't find application.css in /app/public/packs/manifest.json. Possible causes:
  2017-11-19T12:30:56.339768+00:00 app[web.1]: 1. You want to set webpacker.yml value of compile to true for your environment
  2017-11-19T12:30:56.339770+00:00 app[web.1]: 2. Webpack has not yet re-run to reflect updates.
  2017-11-19T12:30:56.339771+00:00 app[web.1]: 3. You have misconfigured Webpacker's config/webpacker.yml file.
  2017-11-19T12:30:56.339769+00:00 app[web.1]:    unless you are using the `webpack -w` or the webpack-dev-server.
  2017-11-19T12:30:56.339772+00:00 app[web.1]: 4. Your Webpack configuration is not creating a manifest.
  2017-11-19T12:30:56.339974+00:00 app[web.1]: [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]     3: &lt;%= javascript_pack_tag 'application' %&gt;
  2017-11-19T12:30:56.340038+00:00 app[web.1]: F, [2017-11-19T12:30:56.339975 #4] FATAL -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]   
  2017-11-19T12:30:56.340104+00:00 app[web.1]: F, [2017-11-19T12:30:56.340050 #4] FATAL -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c] app/views/react_view/index.html.erb:2:in `_app_views_react_view_index_html_erb___547572771215860275_34419720'
  2017-11-19T12:30:56.339974+00:00 app[web.1]: [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]     4: &lt;%= javascript_pack_tag 'ReactHome' %&gt;
  2017-11-19T12:30:56.339773+00:00 app[web.1]: Your manifest contains:
  2017-11-19T12:30:56.339775+00:00 app[web.1]: }
  2017-11-19T12:30:56.339774+00:00 app[web.1]: {
  2017-11-19T12:30:56.339775+00:00 app[web.1]: ):
  2017-11-19T12:30:56.339972+00:00 app[web.1]: F, [2017-11-19T12:30:56.339903 #4] FATAL -- : [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]     1: &lt;script&gt;window.__theme = 'bs4';&lt;/script&gt;
  2017-11-19T12:30:56.339973+00:00 app[web.1]: [0b584fb1-2c9e-41e9-bfe4-19cbf6523a6c]     2: &lt;%= stylesheet_pack_tag 'application' %&gt;
  </code></pre>
  
  <p>`</p>