fix stylesheets compilation with webpack

app/frontend/src/stylesheets/app.printer.scss

@@ -1,3 +1 @@
-/*
- *= require fullcalendar/dist/fullcalendar.print
- */
+@import "~fullcalendar/dist/fullcalendar.print";

config/webpack/loaders/sass.js

@@ -1,17 +1,19 @@
-module.exports = {
-  test: /\.(scss|sass)$/i,
-  use: [
-    {
-      loader: 'css-loader',
-      options: {
-        sourceMap: true
-      }
-    },
-    {
-      loader: 'resolve-url-loader'
-    },
-    {
-      loader: 'sass-loader'
+const getStyleRule = require('@rails/webpacker/package/utils/get_style_rule');
+
+module.exports = getStyleRule(/\.(scss|sass)$/i, false, [
+  {
+    loader: 'resolve-url-loader',
+    options: {
+      sourceMap: true
     }
-  ]
-};
+  },
+  {
+    loader: 'sass-loader',
+    options: {
+      sourceMap: true,
+      sassOptions: {
+        includePaths: ['app/frontend/src/stylesheets']
+      }
+    }
+  }
+]);

config/webpack/loaders/sass_erb.js

@@ -1,9 +1,22 @@
-module.exports = {
-  test: /\.(scss|sass)\.erb$/,
-  enforce: 'pre',
-  exclude: /node_modules/,
-  loader: [
-    'sass-loader',
-    'rails-erb-loader'
-  ]
-};
+const getStyleRule = require('@rails/webpacker/package/utils/get_style_rule');
+
+module.exports = getStyleRule(/\.(scss|sass)\.erb$/, false, [
+  {
+    loader: 'resolve-url-loader',
+    options: {
+      sourceMap: true
+    }
+  },
+  {
+    loader: 'sass-loader',
+    options: {
+      sourceMap: true,
+      sassOptions: {
+        includePaths: ['app/frontend/src/stylesheets']
+      }
+    }
+  },
+  {
+    loader: 'rails-erb-loader'
+  }
+]);

config/webpacker.yml

@@ -16,7 +16,7 @@ default: &default
   cache_manifest: false
 
   # Extract and emit a css file
-  extract_css: false
+  extract_css: true
 
   static_assets_extensions:
     - .jpg