Why FileHelper don't normalize path's by Yii::getAlias()?

[WinterSilence]

extended version:

/**
 * @inheritDoc
 */
class FileHelper extends BaseFileHelper
{
    /**
     * @var string[] An array of path aliases as path/alias pairs
     */
    private static $aliases;
    /**
     * @var int the length of serialized `Yii::$aliases`, using to recalculate `self::$aliases` on
     * change `Yii::$aliases`.
     */
    private static $controlSumAliases = 0;

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function normalizePath($path, $ds = DIRECTORY_SEPARATOR)
    {
        return parent::normalizePath(Yii::getAlias($path), $ds);
    }

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function copyDirectory($src, $dst, $options = [])
    {
        parent::copyDirectory(Yii::getAlias($src), Yii::getAlias($dst), $options);
    }

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function removeDirectory($dir, $options = [])
    {
        parent::removeDirectory(Yii::getAlias($dir), $options);
    }

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function unlink($path)
    {
        parent::unlink(Yii::getAlias($path));
    }

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function createDirectory($path, $mode = 0775, $recursive = true)
    {
        return parent::createDirectory(Yii::getAlias($path), $mode, $recursive);
    }

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function changeOwnership($path, $ownership, $mode = null)
    {
        parent::changeOwnership(Yii::getAlias($path), $ownership, $mode);
    }

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function findDirectories($dir, $options = [])
    {
        return parent::findDirectories(Yii::getAlias($dir), $options);
    }

    /**
     * @inheritDoc
     * @throws \yii\base\Exception
     */
    public static function findFiles($dir, $options = [])
    {
        return parent::findFiles(Yii::getAlias($dir), $options);
    }

    /**
     * Returns flatten list of alias/path pairs.
     *
     * @return array
     */
    public static function getAliases()
    {
        if (!isset(self::$aliases)) {
            self::$aliases = [];
            self::$controlSumAliases = strlen(serialize(Yii::$aliases));
            /** @var string|string[] $basePaths */
            foreach (Yii::$aliases as $alias => $basePaths) {
                if (!is_array($basePaths)) {
                    $basePaths = [$alias => $basePaths];
                }
                foreach ($basePaths as $alias => $basePath) {
                    $basePath = str_replace(['\\', '/'], DIRECTORY_SEPARATOR, $basePath);
                    self::$aliases[$basePath] = $alias;
                }
            }
            // sort by path length (from longest to shortest) for correct work `static::findAlias()`
            uksort(self::$aliases, 'strcmp');
        } elseif (self::$controlSumAliases !== strlen(serialize(Yii::$aliases))) {
            // reset cache on update `Yii::$aliases`
            self::$aliases = null;
        }

        return self::$aliases;
    }

    /**
     * Returns the path alias, this is useful when need mask real path.
     *
     * @param string $path the real path
     * @return string|false
     */
    public static function findAlias($path)
    {
        $path = str_replace(['\\', '/'], DIRECTORY_SEPARATOR, $path);
        foreach (static::getAliases() as $basePath => $alias) {
            $length = strlen($basePath);
            if (strncmp($path, $basePath, $length) === 0) {
                return $alias . substr($path, $length);
            }
        }

        return false;
    }
}

[samdark]

Because it's more low level and deals with file paths. It is like that by design.