Do not load javascripts for disabled plugins (#5103)

* Do not load javascript for disabled plugins

* Appease rubocop

app/assets/javascripts/discourse.js.es6

@@ -1,7 +1,9 @@
 import { buildResolver } from 'discourse-common/resolver';
 import { default as computed, observes } from 'ember-addons/ember-computed-decorators';
+import PreloadStore from 'preload-store';
 
 const _pluginCallbacks = [];
+const _pluginDefinitions = {};
 
 const Discourse = Ember.Application.extend({
   rootElement: '#main',
@@ -101,6 +103,16 @@ const Discourse = Ember.Application.extend({
 
     $('noscript').remove();
 
+    // Load plugin definions.
+    const disabledPlugins = PreloadStore.get('site').disabled_plugins;
+    Object.keys(_pluginDefinitions).forEach((key) => {
+      if(!(disabledPlugins.includes(key))){ // Not disabled, so load it
+        _pluginDefinitions[key].forEach((func) => {
+          func();
+        });
+      }
+    });
+
     Object.keys(requirejs._eak_seen).forEach(function(key) {
       if (/\/pre\-initializers\//.test(key)) {
         const module = requirejs(key, null, null, true);
@@ -154,6 +166,13 @@ const Discourse = Ember.Application.extend({
     _pluginCallbacks.push({ version, code });
   },
 
+  _registerPluginScriptDefinition(pluginName, definition) {
+    if(!(pluginName in _pluginDefinitions)){
+      _pluginDefinitions[pluginName] = [];
+    }
+    _pluginDefinitions[pluginName].push(definition);
+  },
+
   assetVersion: Ember.computed({
     get() {
       return this.get("currentAssetVersion");

config/initializers/014-wrap_plugin_js.rb

@@ -0,0 +1,5 @@
+require 'discourse_wrap_plugin_js'
+
+Rails.application.config.assets.configure do |env|
+  env.register_preprocessor('application/javascript', DiscourseWrapPluginJS)
+end

lib/discourse_wrap_plugin_js.rb

@@ -0,0 +1,31 @@
+class DiscourseWrapPluginJS
+  def initialize(options = {}, &block)
+  end
+
+  def self.instance
+    @instance ||= new
+  end
+
+  def self.call(input)
+    instance.call(input)
+  end
+
+  # Add stuff around javascript
+  def call(input)
+    path = input[:environment].context_class.new(input).pathname.to_s
+    data = input[:data]
+
+    # Only apply to plugin paths
+    return data unless (path =~ /\/plugins\//)
+
+    # Find the folder name of the plugin
+    folder_name = path[/\/plugins\/(\S+?)\//, 1]
+
+    # Lookup plugin name
+    plugin = Discourse.plugins.find { |p| p.path =~ /\/plugins\/#{folder_name}\// }
+    plugin_name = plugin.name
+
+    "Discourse._registerPluginScriptDefinition('#{plugin_name}', function(){#{data}}); \n"
+  end
+
+end