Why isn't the Endroid\QrCode\QrCode found?

Question

I created a custom module and installed the endroid/qrcode library in my module using Composer. When I try to use that library, I get the following error.

Error: Class 'Endroid\QrCode\QrCode' not found in Drupal\shopexp\Plugin\Block\ShopExp->build() (line 25 of modules\custom\shopexp\src\Plugin\Block\ShopExp.php).

The code using the library is the following one.

namespace Drupal\shopexp\Plugin\Block;
use Drupal\Core\Block\BlockBase;
use Endroid\QrCode\QrCode;

class ShopExp extends BlockBase {    
  public function createpr() {
      $qr = QrCode::create("https://site.com");
  }  
  public function build() {
    $qr = new QrCode();
    return [
      '#markup' => 'test msg',
    ];
  }
}

The composer.json file used by the module is the following one.

{
    "require": {
        "endroid/qr-code": "^2.5"
    }
}

The folder structure is the following one.

Answer 1

You have to composer require endroid/qrcode from the Drupal root directory, not from your custom module directory. The package needs to be installed in the main vendor directory along with all the other packages used by Drupal, otherwise the class loader can't find it.