Yii2 一个隐藏的小坑，致使我的组件的bootstrap方法执行了多次。

昨天，我通过日志打印，发现我的store 组件的bootstrap在初始化的时候被莫名的执行了两次，日志如下：

store
(),fecshop\services\Store::actionBootstrap()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/services/Service.php(58),::call_user_func_array()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Service::__call()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(316),fecshop\components\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/web/Application.php(66),yii\base\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(267),yii\web\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Object.php(107),yii\base\Application::init()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(206),yii\base\Object::__construct()
/www/web/develop/fecshop/appfront/web/index.php(44),yii\base\Application::__construct()


store
(),fecshop\services\Store::actionBootstrap()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/services/Service.php(58),::call_user_func_array()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Service::__call()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(316),fecshop\components\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/web/Application.php(66),yii\base\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(267),yii\web\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Object.php(107),yii\base\Application::init()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(206),yii\base\Object::__construct()
/www/web/develop/fecshop/appfront/web/index.php(44),yii\base\Application::__construct()

最终找到了原因，步骤如下：

对于Yii2的方法：

yii\helpers\ArrayHelper::merge();

我们知道，对于数组中key为数字的部分，譬如：

yii\helpers\ArrayHelper::merge(['store','view'],['log','store']);
合并后的结果为 ['store','log','view','store'] ,而不是 ['store','log','view']

对于yii2的bootstrap，我写了一个store组件，然后，没有注意到，在两个地方加入了这个配置：

'bootstrap' => ['store'],

bootstrap的执行代码在：

yii\base\Application的bootstrap()方法中，大约298行出的代码：

foreach ($this->bootstrap as $class) {
            $component = null;
            if (is_string($class)) {
                if ($this->has($class)) {
                    $component = $this->get($class);
                } elseif ($this->hasModule($class)) {
                    $component = $this->getModule($class);
                } elseif (strpos($class, '\\') === false) {
                    throw new InvalidConfigException("Unknown bootstrapping component ID: $class");
                }
            }
            if (!isset($component)) {
                $component = Yii::createObject($class);
            }

            if ($component instanceof BootstrapInterface) {
                Yii::trace('Bootstrap with ' . get_class($component) . '::bootstrap()', __METHOD__);
                $component->bootstrap($this);
            } else {
                Yii::trace('Bootstrap with ' . get_class($component), __METHOD__);
            }
        }

我加了下打印，

foreach ($this->bootstrap as $class) {
     echo $class.'<br/>';
           $component = null;
           if (is_string($class)) {
               if ($this->has($class)) {
                   $component = $this->get($class);
               } elseif ($this->hasModule($class)) {
                   $component = $this->getModule($class);
               } elseif (strpos($class, '\\') === false) {
                   throw new InvalidConfigException("Unknown bootstrapping component ID: $class");
               }
           }
           if (!isset($component)) {
               $component = Yii::createObject($class);
           }

           if ($component instanceof BootstrapInterface) {
               Yii::trace('Bootstrap with ' . get_class($component) . '::bootstrap()', __METHOD__);
               $component->bootstrap($this);
           } else {
               Yii::trace('Bootstrap with ' . get_class($component), __METHOD__);
           }
       }

然后在调用组件的地方：

然后在Store组件的bootstrap方法中加入

public function bootstrap($app){
    $d = debug_backtrace();
    foreach($d as $e){
      $function = $e['function'];
      $class = $e['class'];
      $file = $e['file'];
      $line = $e['line'];
      echo $file.'('.$line.'),'.
      $class.'::'.$function.'()<br/>';
    }
    echo '<br/><br/>';

通过debug_backtrace()，进行打印输出：

结果如下：

debug
gii
store
(),fecshop\services\Store::actionBootstrap()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/services/Service.php(58),::call_user_func_array()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Service::__call()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(316),fecshop\components\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/web/Application.php(66),yii\base\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(267),yii\web\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Object.php(107),yii\base\Application::init()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(206),yii\base\Object::__construct()
/www/web/develop/fecshop/appfront/web/index.php(44),yii\base\Application::__construct()


store
(),fecshop\services\Store::actionBootstrap()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/services/Service.php(58),::call_user_func_array()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Service::__call()
/www/web/develop/fecshop/vendor/fancyecommerce/fecshop/components/Store.php(22),fecshop\services\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(316),fecshop\components\Store::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/web/Application.php(66),yii\base\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(267),yii\web\Application::bootstrap()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Object.php(107),yii\base\Application::init()
/www/web/develop/fecshop/vendor/yiisoft/yii2/base/Application.php(206),yii\base\Object::__construct()
/www/web/develop/fecshop/appfront/web/index.php(44),yii\base\Application::__construct()

发现我的store 组件确实被执行了2次，

原因就是，\appfront\config\fecshop_local.php加入了配置：对store组件的配置

return [
  'modules'=>$modules,
  'bootstrap' => ['store'],
    'services' => $services,
];

在另外一个地方，我也加入了配置：

'modules'=>$modules,
  /* only config in front web */
  'bootstrap' => ['store'],
  'params'	=> [
    /* appfront base theme dir   */
    'appfrontBaseTheme' 	=> '@fecshop/app/appfront/theme/base/front',
    'appfrontBaseLayoutName'=> 'main.php',
  ],

造成store组件的bootstrap被执行了两次，

不知道为什么yii2，不在这里执行一次数组的array_unique方法,

不然配置乱了，在很多地方配置了bootstrap方法，但是又没有注意到，尤其是bootstrap()方法在每次初始化的时候都要执行，造成额外开销，这个小坑，还是得通过打印$config的方式查看。