title: stylesheet_pack_tag not finding app/javascript/src/application.css in rails 5.1 with webpacker gem
body: <p>I am receiving this error when I try to load a page in my new rails 5.1 app using webpacker. I would like webpacker to handle CSS as well. </p>
  
  <pre><code>Started GET "/" for ::1 at 2017-09-01 12:20:23 -0400
  Processing by HomeController#welcome as HTML
    Rendering home/welcome.html.erb within layouts/application
    Rendered home/welcome.html.erb within layouts/application (0.4ms)
  Completed 500 Internal Server Error in 28ms
  
  
  
  ActionView::Template::Error (Webpacker can't find application.css in /Users/myusername/Documents/testing-ground/myapp/public/packs/manifest.json. Possible causes:
  1. You want to set wepbacker.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:
  {
    "application.js": "/packs/application-1ba6db9cf5c0fb48c785.js",
    "hello_react.js": "/packs/hello_react-812cbb4d606734bec7a9.js"
  }
  ):
       7:     &lt;%= stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track': 'reload' %&gt;
       8:     &lt;%= javascript_include_tag 'application', 'data-turbolinks-track': 'reload' %&gt;
       9:     &lt;%= javascript_pack_tag 'application' %&gt;
      10: &lt;%= stylesheet_pack_tag 'application' %&gt;
      11:   &lt;/head&gt;
      12:
      13:   &lt;body&gt;
  
  app/views/layouts/application.html.erb:10:in `_app_views_layouts_application_html_erb__1178607493020013329_70339213085820'
  </code></pre>
  
  <p>I am running the <code>./bin/webpack-dev-server</code> alongside the <code>rails server</code>. I created the app using: </p>
  
  <p><code>rails new myapp --webpack</code> 
  <code>bundle</code>
  <code>bundle exec rails webpacker:install:react</code></p>
  
  <p>I have a single CSS file <code>app/javascript/src/application.css</code>. (Writing that makes me feel something is wrong. Putting css inside of a javascript directory seems improper.)</p>
  
  <p>I just have single root route defined <code>root to: 'home#welcome'</code>.</p>
  
  <p>Here is <code>app/views/layouts/application.html.erb</code></p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
    &lt;head&gt;
      &lt;title&gt;Myapp&lt;/title&gt;
      &lt;%= csrf_meta_tags %&gt;
  
      &lt;%= javascript_pack_tag 'application' %&gt;
      &lt;%= stylesheet_pack_tag 'application' %&gt;
    &lt;/head&gt;
  
    &lt;body&gt;
      &lt;%= yield %&gt;
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Here is my <code>config/webpacker.yml</code> (I have tried also setting compile to <code>false</code> in development.</p>
  
  <pre><code># Note: You must restart bin/webpack-dev-server for changes to take effect
  
  default: &amp;default
    source_path: app/javascript
    source_entry_path: packs
    public_output_path: packs
    cache_path: tmp/cache/webpacker
  
    # Additional paths webpack should lookup modules
    # ['app/assets', 'engine/foo/app/assets']
    resolved_paths: []
  
    # Reload manifest.json on all requests so we reload latest compiled packs
    cache_manifest: false
  
    extensions:
      - .coffee
      - .erb
      - .js
      - .jsx
      - .ts
      - .vue
      - .sass
      - .scss
      - .css
      - .png
      - .svg
      - .gif
      - .jpeg
      - .jpg
  
  development:
    &lt;&lt;: *default
    compile: true
  
    dev_server:
      host: localhost
      port: 3035
      hmr: false
      https: false
  
  test:
    &lt;&lt;: *default
    compile: true
  
    # Compile test packs to a separate directory
    public_output_path: packs-test
  
  production:
    &lt;&lt;: *default
  
    # Production demands on precompilation of packs prior to booting for performance.
    compile: false
  
    # Cache manifest.json for performance
    cache_manifest: true
  </code></pre>
  
  <p>I don't want to add too many details up-front incase they are more distracting then helpful. Please ask for anything else and I'll add to my question. Thanks!</p>