Yii2. Invalid path alias - yii2

Question

I've seen similiar questions but haven't found a working solution. Here is my index.php file:
<?php
// comment out the following two lines when deployed to production
defined('YII_DEBUG') or define('YII_DEBUG', true);
defined('YII_ENV') or define('YII_ENV', 'dev');
require(__DIR__ . '/../vendor/autoload.php');
require(__DIR__ . '/../vendor/yiisoft/yii2/Yii.php');
$config = require(__DIR__ . '/../config/web.php');
(new yii\web\Application($config))->run();
require(__DIR__ . '/../config/aliases.php');
As you can see, it requires config/aliases.php file, whose contents are:
<?php
Yii::setAlias('message_files_root', '#webroot/message_files');
Yii::setAlias('message_files', '#web/message_files');
CallingYii::getAlias('#message_files_root') works fine within the index.php, but when it is in a controller file, it says Invalid path alias: #message_files_root.
Here is my controller's action (the rest of the code is fully commented):
public function actionIndex()
{
var_dump(Yii::getAlias('#message_files_root'));
$message = new Message();

Answer 1

if you invoke Yii::getAlias() static method from controller, Yii::setAlias(#web) does not get register yet.
you may refer to the web/index file.
web/index.php
require(__DIR__ . '/../../vendor/autoload.php');
require(__DIR__ . '/../../vendor/yiisoft/yii2/Yii.php');
require(__DIR__ . '/../../common/config/bootstrap.php'); --> Yii::setAlias(#web) are not listed here
require(__DIR__ . '/../config/bootstrap.php');
$config = yii\helpers\ArrayHelper::merge(
require(__DIR__ . '/../../common/config/main.php'),
require(__DIR__ . '/../../common/config/main-local.php'),
require(__DIR__ . '/../config/main.php'),
require(__DIR__ . '/../config/main-local.php')
);
$application = new yii\web\Application($config);
//var_dump(Yii::getAlias('#web'));die; --> imitate invoke #web alias fail
$application->run(); --> here both #web alias and aliases from $config got registered.
//var_dump(Yii::getAlias('#web'));die; --> imitate invoke #web alias success
my guess is, the config got registered first before the default #web aliases being register. Thats why invoking #web aliases from bootrap config fail.
thus, u need to use absolute path for the second paramter. use this..
yii2 advanced template
Yii::setAlias('#message_files_root', dirname(dirname(__DIR__)) . '/frontend/web/message_files');
yii2 basic template
Yii::setAlias('#message_files_root', dirname(__DIR__) . '/web/message_files');

Answer 2

I am NOT claiming that is the nicest way to do that, but it works the way I wanted it to work – when an alias can include other aliases.
<?php
// comment out the following two lines when deployed to production
defined('YII_DEBUG') or define('YII_DEBUG', true);
defined('YII_ENV') or define('YII_ENV', 'dev');
require(__DIR__ . '/../vendor/autoload.php');
require(__DIR__ . '/../vendor/yiisoft/yii2/Yii.php');
$config = require(__DIR__ . '/../config/web.php');
$app = new class($config) extends yii\web\Application
{
protected function bootstrap()
{
parent::bootstrap();
require(__DIR__ . '/../config/aliases.php');
}
};
$app->run();