Removed `Application::preload` in favor of `Application::bootstrap`

apps/advanced/backend/config/main.php

@@ -9,7 +9,6 @@ $params = array_merge(
 return [
     'id' => 'app-backend',
     'basePath' => dirname(__DIR__),
-    'preload' => ['log'],
     'controllerNamespace' => 'backend\controllers',
     'modules' => [],
     'components' => [

apps/advanced/environments/dev/backend/config/main-local.php

@@ -4,7 +4,7 @@ $config = [];
 
 if (!YII_ENV_TEST) {
     // configuration adjustments for 'dev' environment
-    $config['preload'][] = 'debug';
+    $config['bootstrap'][] = 'debug';
     $config['modules']['debug'] = 'yii\debug\Module';
     $config['modules']['gii'] = 'yii\gii\Module';
 }

apps/advanced/environments/dev/frontend/config/main-local.php

@@ -4,7 +4,7 @@ $config = [];
 
 if (!YII_ENV_TEST) {
     // configuration adjustments for 'dev' environment
-    $config['preload'][] = 'debug';
+    $config['bootstrap'][] = 'debug';
     $config['modules']['debug'] = 'yii\debug\Module';
     $config['modules']['gii'] = 'yii\gii\Module';
 }

apps/basic/config/console.php

@@ -8,7 +8,6 @@ $db = require(__DIR__ . '/db.php');
 return [
     'id' => 'basic-console',
     'basePath' => dirname(__DIR__),
-    'preload' => ['log'],
     'controllerNamespace' => 'app\commands',
     'extensions' => require(__DIR__ . '/../vendor/yiisoft/extensions.php'),
     'components' => [

apps/basic/config/web.php

@@ -38,7 +38,7 @@ $config = [
 
 if (YII_ENV_DEV) {
     // configuration adjustments for 'dev' environment
-    $config['preload'][] = 'debug';
+    $config['bootstrap'][] = 'debug';
     $config['modules']['debug'] = 'yii\debug\Module';
     $config['modules']['gii'] = 'yii\gii\Module';
 }

docs/guide/extensions.md

@@ -129,9 +129,9 @@ namespace myname\mywidget;
 use yii\base\BootstrapInterface;
 use yii\base\Application;
 
-class Bootstrap implements BootstrapInterface
+class MyBootstrapClass implements BootstrapInterface
 {
-    public function bootstrap(Application $app)
+    public function bootstrap($app)
     {
         $app->on(Application::EVENT_BEFORE_REQUEST, function () {
              // do something here
@@ -145,7 +145,7 @@ You then list this bootstrap class in `composer.json` as follows,
 ```json
 {
     "extra": {
-        "bootstrap": "path\\to\\MyBootstrapClass"
+        "bootstrap": "myname\\mywidget\\MyBootstrapClass"
     }
 }
 ```

docs/guide/gii.md

@@ -58,7 +58,7 @@ In basic application template configuration structure is a bit different so Gii
 if (YII_ENV_DEV)
 {
     // configuration adjustments for 'dev' environment
-    $config['preload'][] = 'debug';
+    $config['bootstrap'][] = 'debug';
     $config['modules']['debug'] = 'yii\debug\Module';
     $config['modules']['gii'] = 'yii\gii\Module'; // <--- here
 }
@@ -70,7 +70,7 @@ So in order to adjust IP address you need to do it like the following:
 if (YII_ENV_DEV)
 {
     // configuration adjustments for 'dev' environment
-    $config['preload'][] = 'debug';
+    $config['bootstrap'][] = 'debug';
     $config['modules']['debug'] = 'yii\debug\Module';
     $config['modules']['gii'] = [
         'class' => 'yii\gii\Module',

docs/guide/module-debug.md

@@ -23,7 +23,7 @@ Installing and configuring
 To enable these features, add these lines to your configuration file to enable the debug module:
 
 ```php
-'preload' => ['debug'],
+'bootstrap' => ['debug'],
 'modules' => [
     'debug' => 'yii\debug\Module',
 ]
@@ -32,7 +32,7 @@ To enable these features, add these lines to your configuration file to enable t
 By default, the debug module only works when browsing the website from localhost. If you want to use it on a remote (staging) server, add the parameter `allowedIPs` to the configuration to whitelist your IP:
 
 ```php
-'preload' => ['debug'],
+'bootstrap' => ['debug'],
 'modules' => [
     'debug' => [
         'class' => 'yii\debug\Module',
@@ -169,7 +169,7 @@ Now it's time to tell the debugger to use the new panel. In `config/web.php`, th
 ```php
 if (YII_ENV_DEV) {
     // configuration adjustments for 'dev' environment
-    $config['preload'][] = 'debug';
+    $config['bootstrap'][] = 'debug';
     $config['modules']['debug'] = [
         'class' => 'yii\debug\Module',
         'panels' => [

extensions/debug/Module.php

@@ -9,6 +9,7 @@ namespace yii\debug;
 
 use Yii;
 use yii\base\Application;
+use yii\base\BootstrapInterface;
 use yii\helpers\Url;
 use yii\web\View;
 use yii\web\ForbiddenHttpException;
@@ -19,7 +20,7 @@ use yii\web\ForbiddenHttpException;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class Module extends \yii\base\Module
+class Module extends \yii\base\Module implements BootstrapInterface
 {
     /**
      * @var array the list of IPs that are allowed to access this module.
@@ -72,10 +73,6 @@ class Module extends \yii\base\Module
         parent::init();
         $this->dataPath = Yii::getAlias($this->dataPath);
         $this->logTarget = Yii::$app->getLog()->targets['debug'] = new LogTarget($this);
-        // do not initialize view component before application is ready (needed when debug in preload)
-        Yii::$app->on(Application::EVENT_BEFORE_REQUEST, function () {
-            Yii::$app->getView()->on(View::EVENT_END_BODY, [$this, 'renderToolbar']);
-        });
 
         // merge custom panels and core panels so that they are ordered mainly by custom panels
         if (empty($this->panels)) {
@@ -100,6 +97,17 @@ class Module extends \yii\base\Module
     /**
      * @inheritdoc
      */
+    public function bootstrap($app)
+    {
+        // delay attaching event handler to the view component after it is fully configured
+        $app->on(Application::EVENT_BEFORE_REQUEST, function () use ($app) {
+            $app->getView()->on(View::EVENT_END_BODY, [$this, 'renderToolbar']);
+        });
+    }
+
+    /**
+     * @inheritdoc
+     */
     public function beforeAction($action)
     {
         Yii::$app->getView()->off(View::EVENT_END_BODY, [$this, 'renderToolbar']);

extensions/debug/README.md

@@ -33,7 +33,7 @@ Once the extension is installed, simply modify your application configuration as
 
 ```php
 return [
-	'preload' => ['debug'],
+	'bootstrap' => ['debug'],
 	'modules' => [
 		'debug' => 'yii\debug\Module',
 		...

extensions/elasticsearch/README.md

@@ -176,7 +176,7 @@ enabled, it is sufficient to just add the panels configuration):
 
 ```php
 	// ...
-	'preload' => 'debug',
+	'bootstrap' => ['debug'],
 	'modules' => [
 		'debug' => [
 			'class' => 'yii\\debug\\Module',

framework/CHANGELOG.md

@@ -279,6 +279,7 @@ Yii Framework 2 Change Log
 - Chg: Removed `yii\grid\Column::getDataCellContent()` and renamed `yii\grid\DataColumn::getDataCellContent()` to `yii\grid\DataColumn::getDataCellValue()` (cebe)
 - Chg: `yii\log\Logger` is split into `yii\log\Logger` and `yii\log\Dispatcher`. (qiangxue)
 - Chg: Moved all filter classes to namespace `yii\filters` (qiangxue)
+- Chg: Removed `Application::preload` in favor of `Application::bootstrap` (qiangxue)
 - New #66: [Auth client library](https://github.com/yiisoft/yii2-authclient) OpenId, OAuth1, OAuth2 clients (klimov-paul)
 - New #303: Added built-in support for REST API (qiangxue)
 - New #503: Added `yii\di\Container` and `yii\di\ServiceLocator` (qiangxue)

framework/base/Application.php

@@ -8,8 +8,6 @@
 namespace yii\base;
 
 use Yii;
-use yii\helpers\Console;
-use yii\web\HttpException;
 
 /**
  * Application is the base class for all application classes.
@@ -145,9 +143,19 @@ abstract class Application extends Module
      */
     public $extensions = [];
     /**
-     * @var array list of bootstrap classes or their configurations. A bootstrap class must implement
-     * [[BootstrapInterface]]. The [[BootstrapInterface::bootstrap()]] method of each bootstrap class
-     * will be invoked at the beginning of [[init()]].
+     * @var array list of bootstrap components that should be run right after
+     * the application is configured.
+     *
+     * Each bootstrap component may be specified in one of the following formats:
+     *
+     * - an application component ID as specified via [[components]].
+     * - a module ID as specified via [[modules]].
+     * - a class name.
+     * - a configuration array.
+     *
+     * Note that a bootstrap component must implement [[BootstrapInterface]], or an exception will be thrown.
+     * The [[BootstrapInterface::bootstrap()]] method of each bootstrap component will be called
+     * when the component is instantiated and run in in [[bootstrap()]].
      */
     public $bootstrap = [];
     /**
@@ -233,45 +241,53 @@ abstract class Application extends Module
     public function init()
     {
         $this->state = self::STATE_INIT;
-
-        $this->initExtensions($this->extensions);
-        foreach ($this->bootstrap as $class) {
-            /** @var BootstrapInterface $bootstrap */
-            $bootstrap = Yii::createObject($class);
-            $bootstrap->bootstrap($this);
-        }
-        parent::init();
+        $this->get('log');
+        $this->bootstrap();
     }
 
     /**
-     * Initializes the extensions.
-     * @param array $extensions the extensions to be initialized. Please refer to [[extensions]]
-     * for the structure of the extension array.
+     * Initializes extensions and executes bootstrap components.
+     * This method is called by [[init()]] after the application has been fully configured.
+     * If you override this method, make sure you also call the parent implementation.
+     * @throws InvalidConfigException if a bootstrap component does not implement BootstrapInterface
      */
-    protected function initExtensions($extensions)
+    protected function bootstrap()
     {
-        foreach ($extensions as $extension) {
+        foreach ($this->extensions as $extension) {
             if (!empty($extension['alias'])) {
                 foreach ($extension['alias'] as $name => $path) {
                     Yii::setAlias($name, $path);
                 }
             }
             if (isset($extension['bootstrap'])) {
-                /** @var BootstrapInterface $bootstrap */
-                $bootstrap = Yii::createObject($extension['bootstrap']);
-                $bootstrap->bootstrap($this);
+                $component = Yii::createObject($extension['bootstrap']);
+                if ($component instanceof BootstrapInterface) {
+                    $component->bootstrap($this);
+                } else {
+                    $class = is_array($extension['bootstrap']) ? $extension['bootstrap']['class'] : $extension['bootstrap'];
+                    throw new InvalidConfigException("$class must implement \\yii\\base\\BootstrapInterface");
                 }
             }
         }
 
-    /**
-     * Loads components that are declared in [[preload]].
-     * @throws InvalidConfigException if a component or module to be preloaded is unknown
-     */
-    public function preloadComponents()
-    {
-        $this->get('log');
-        parent::preloadComponents();
+        foreach ($this->bootstrap as $class) {
+            if (is_string($class)) {
+                if ($this->has($class)) {
+                    $component = $this->get($class);
+                } elseif ($this->hasModule($class)) {
+                    $component = $this->getModule($class);
+                }
+            }
+            if (!isset($component)) {
+                $component = Yii::createObject($class);
+            }
+
+            if ($component instanceof BootstrapInterface) {
+                $component->bootstrap($this);
+            } else {
+                throw new InvalidConfigException((is_array($class) ? $class['class'] : $class) . " must implement \\yii\\base\\BootstrapInterface");
+            }
+        }
     }
 
     /**

framework/base/BootstrapInterface.php

@@ -56,5 +56,5 @@ interface BootstrapInterface
      * Bootstrap method to be called during application bootstrap stage.
      * @param Application $app the application currently running
      */
-    public function bootstrap(Application $app);
+    public function bootstrap($app);
 }

framework/base/Module.php

@@ -52,10 +52,6 @@ class Module extends ServiceLocator
      */
     public $params = [];
     /**
-     * @var array the IDs of the components or modules that should be preloaded right after initialization.
-     */
-    public $preload = [];
-    /**
      * @var string an ID that uniquely identifies this module among other modules which have the same [[module|parent]].
      */
     public $id;
@@ -137,9 +133,10 @@ class Module extends ServiceLocator
 
     /**
      * Initializes the module.
+     *
      * This method is called after the module is created and initialized with property values
-     * given in configuration. The default implementation will call [[preloadComponents()]] to
-     * load components that are declared in [[preload]].
+     * given in configuration. The default implementation will initialize [[controllerNamespace]]
+     * if it is not set.
      *
      * If you override this method, please make sure you call the parent implementation.
      */
@@ -151,7 +148,6 @@ class Module extends ServiceLocator
                 $this->controllerNamespace = substr($class, 0, $pos) . '\\controllers';
             }
         }
-        $this->preloadComponents();
     }
 
     /**
@@ -407,23 +403,6 @@ class Module extends ServiceLocator
     }
 
     /**
-     * Loads components that are declared in [[preload]].
-     * @throws InvalidConfigException if a component or module to be preloaded is unknown
-     */
-    public function preloadComponents()
-    {
-        foreach ($this->preload as $id) {
-            if ($this->has($id)) {
-                $this->get($id);
-            } elseif ($this->hasModule($id)) {
-                $this->getModule($id);
-            } else {
-                throw new InvalidConfigException("Unknown component or module: $id");
-            }
-        }
-    }
-
-    /**
      * Runs a controller action specified by a route.
      * This method parses the specified route and creates the corresponding child module(s), controller and action
      * instances. It then calls [[Controller::runAction()]] to run the action with the given parameters.

framework/web/Application.php

@@ -56,12 +56,13 @@ class Application extends \yii\base\Application
     /**
      * @inheritdoc
      */
-    public function preloadComponents()
+    protected function bootstrap()
     {
-        parent::preloadComponents();
         $request = $this->getRequest();
         Yii::setAlias('@webroot', dirname($request->getScriptFile()));
         Yii::setAlias('@web', $request->getBaseUrl());
+
+        parent::bootstrap();
     }
 
     /**