Exclude unused hljs languages from bundle

app/server/static/components/hljsLanguages.js

@@ -0,0 +1 @@
+module.exports = ['json'];

app/server/static/components/uploadMixin.js

@@ -1,7 +1,15 @@
-import hljs from 'highlight.js';
+import hljs from 'highlight.js/lib/highlight';
+import hljsLanguages from './hljsLanguages';
 import HTTP, { newHttpClient } from './http';
 import Messages from './messages.vue';
 
+hljsLanguages.forEach((languageName) => {
+  /* eslint-disable import/no-dynamic-require, global-require */
+  const languageModule = require(`highlight.js/lib/languages/${languageName}`);
+  /* eslint-enable import/no-dynamic-require, global-require */
+  hljs.registerLanguage(languageName, languageModule);
+});
+
 export default {
   components: { Messages },
 

app/server/static/webpack.config.js

@@ -3,6 +3,8 @@ const path = require('path');
 const process = require('process');
 const BundleTracker = require('webpack-bundle-tracker');
 const VueLoaderPlugin = require('vue-loader/lib/plugin')
+const { ContextReplacementPlugin } = require('webpack');
+const hljsLanguages = require('./components/hljsLanguages');
 
 const devMode = process.env.DEBUG !== 'False';
 const hotReload = process.env.HOT_RELOAD === '1';
@@ -58,6 +60,10 @@ module.exports = {
         ]
     },
     plugins: [
+        new ContextReplacementPlugin(
+            /highlight\.js\/lib\/languages$/,
+            new RegExp(`^./(${hljsLanguages.join('|')})$`)
+        ),
         new BundleTracker({ filename: './webpack-stats.json' }),
         new VueLoaderPlugin()
     ],