($callback) must be a valid callback

Question

My extension is failing varnish test over and over again and the only visible error i have found in the error reports is

call_user_func(): Argument #1 ($callback) must be a valid callback, class " \n FME\ProductsList\Setup\Patch\Data\EnableProductsList" not found#0 /app/vend \n or/magento/framework/Setup/Patch/PatchRegistry.php(141): call_user_func(Arr \n ay) \n #1 /app/vendor/magento/framework/Setup/Patch/PatchRegistry.php(207): Magent \n o\Framework\Setup\Patch\PatchRegistry->getDependencies('FME\\ProductsLis... \n ')

Here is my code for Data Patch which seems to be fine

<?php
declare (strict_types = 1);
namespace FME\ProductsList\Setup\Patch\Data;

use Magento\Eav\Model\Entity\Attribute\ScopedAttributeInterface;
use Magento\Eav\Setup\EavSetup;
use Magento\Eav\Setup\EavSetupFactory;
use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Framework\Setup\Patch\DataPatchInterface;

class EnableProductsList implements DataPatchInterface
{
    private $moduleDataSetup;
    private $eavSetupFactory;
    public function __construct(
        ModuleDataSetupInterface $moduleDataSetup,
        EavSetupFactory $eavSetupFactory
    ) {
        $this->moduleDataSetup = $moduleDataSetup;
        $this->eavSetupFactory = $eavSetupFactory;
    }
    public function apply()
    {
        $this->moduleDataSetup->startSetup();
        $eavSetup = $this->eavSetupFactory->create(['setup' => $this->moduleDataSetup]);
        $eavSetup->addAttribute(
            'catalog_product', 'enable_productslist', [
                'type' => 'int',
                'backend' => '',
                'frontend' => '',
                'label' => 'Enable Product Export',
                'input' => 'boolean',
                'class' => '',
                'source' => 'Magento\Eav\Model\Entity\Attribute\Source\Boolean',
                'global' => ScopedAttributeInterface::SCOPE_GLOBAL,
                'visible' => true,
                'required' => false,
                'user_defined' => false,
                'default' => 0,
                'note'     => 'This setting was added by FME Product List',
                'searchable' => false,
                'filterable' => false,
                'comparable' => false,
                'visible_on_front' => false,
                'used_in_product_listing' => true,
                'unique' => false,
                'apply_to' => '',
            ]
        );
        $this->moduleDataSetup->endSetup();
    }
    public static function getDependencies()
    {
        return [];
    }
    public function getAliases()
    {
        return [];
    }
}
                                            

Answer 1

The problem was in the composer.json file by mistakenly I have given wrong spellings in psr-4 section

"psr-4": {
    "FME\\ProducstList\\": ""
} 

It should be

"psr-4": {
    "FME\\ProductsList\\": ""
} 

Answer 2

I was also facing the same issue in my custom module installation from the composer. After that, I reviewed my module composer.json and we found that the psr-4.

"name": "prince/Learningmodule",
"psr-4": {
        "Prince\\Learningmodule\\": ""
    }

• The psr-4 values are wrong because My Moduele Vendor name and module name are as

  • Vendor: Prince
  • Module: LearningModule

_Updated code:

"name": "prince/Learningmodule",
"psr-4": {
        "Prince\\LearningModule\\": ""
    }

Please be careful about this naming of PSR-4 It maps your module.

Hope this helps you.