move enabled check into it's own mixin, and cleaned up how you disable a plugin

src/server/kbn_server.js

@@ -28,7 +28,10 @@ module.exports = class KbnServer {
       // find plugins and set this.plugins
       require('./plugins/scan'),
 
-      // make sure that all plugins expect the current version of Kibana
+      // disable the plugins that are disabled through configuration
+      require('./plugins/check_enabled'),
+
+      // disable the plugins that are incompatible with the current version of Kibana
       require('./plugins/check_version'),
 
       // tell the config we are done loading plugins

src/server/plugins/check_enabled.js

@@ -0,0 +1,15 @@
+import toPath from 'lodash/internal/toPath';
+
+export default async function (kbnServer, server, config) {
+  const { plugins } = kbnServer;
+
+  for (let plugin of plugins) {
+    const enabledInConfig = config.get([...toPath(plugin.configPrefix), 'enabled']);
+
+    if (!enabledInConfig) {
+      plugins.disable(plugin);
+    }
+  }
+
+  return;
+};

src/server/plugins/check_version.js

@@ -24,7 +24,7 @@ export default async function (kbnServer, server, config) {
     if (!compatibleWithKibana(kbnServer, plugin)) {
       const message = `Plugin "${name}" was disabled because it expected Kibana version "${version}", and found "${kbnServer.version}".`;
       warningMessages.add(message);
-      plugins.delete(plugin);
+      plugins.disable(plugin);
     }
   }
 

src/server/plugins/plugin.js

@@ -1,5 +1,4 @@
 import _ from 'lodash';
-import toPath from 'lodash/internal/toPath';
 import Joi from 'joi';
 import Bluebird, { attempt, fromNode } from 'bluebird';
 import { basename, resolve } from 'path';
@@ -68,7 +67,7 @@ module.exports = class Plugin {
     this.externalPreInit = opts.preInit || _.noop;
     this.externalInit = opts.init || _.noop;
     this.configPrefix = opts.configPrefix || this.id;
-    this.getConfigSchema = opts.config || _.noop;
+    this.getExternalConfigSchema = opts.config || _.noop;
     this.preInit = _.once(this.preInit);
     this.init = _.once(this.init);
     this[extendInitFns] = [];
@@ -95,16 +94,11 @@ module.exports = class Plugin {
     };
   }
 
-  async readConfigSchema() {
-    let schema = await this.getConfigSchema(Joi);
+  async getConfigSchema() {
+    let schema = await this.getExternalConfigSchema(Joi);
     return schema || defaultConfigSchema;
   }
 
-  get enabled() {
-    const { config } = this.kbnServer;
-    return config.get([...toPath(this.configPrefix), 'enabled']);
-  }
-
   async preInit() {
     return await this.externalPreInit(this.kbnServer.server);
   }

src/server/plugins/plugin_collection.js

@@ -9,7 +9,7 @@ let byIdCache = Symbol('byIdCache');
 let pluginApis = Symbol('pluginApis');
 
 async function addPluginConfig(pluginCollection, plugin) {
-  const configSchema = await plugin.readConfigSchema();
+  const configSchema = await plugin.getConfigSchema();
   let { config } = pluginCollection.kbnServer;
   config.extendSchema(plugin.configPrefix, configSchema);
 }
@@ -44,19 +44,14 @@ module.exports = class Plugins extends Collection {
         throw new TypeError('unexpected plugin export ' + inspect(plugin));
       }
 
-      await this.add(plugin);
-      if (!plugin.enabled) this.delete(plugin);
+      await addPluginConfig(this, plugin);
+      this.add(plugin);
     }
   }
 
-  async add(plugin) {
-    await addPluginConfig(this, plugin);
-    super.add(plugin);
-  }
-
-  delete(plugin) {
+  async disable(plugin) {
     removePluginConfig(this, plugin);
-    super.delete(plugin);
+    this.delete(plugin);
   }
 
   get byId() {