Constant name is expected

[BYK]

After I executed the CLI commands showing an below error

When I'm trying to access front end admin panel throwing an below error.

Fatal error: Uncaught InvalidArgumentException: Constant name is expected. in /var/www/html/vendor/magento/framework/Data/Argument/Interpreter/Constant.php:23 Stack trace: #0 /var/www/html/vendor/magento/framework/Data/Argument/Interpreter/Composite.php(61): Magento\Framework\Data\Argument\Interpreter\Constant->evaluate(Array) #1 /var/www/html/vendor/magento/framework/ObjectManager/Config/Mapper/Dom.php(102): Magento\Framework\Data\Argument\Interpreter\Composite->evaluate(Array) #2 /var/www/html/vendor/magento/framework/Config/Reader/Filesystem.php(176): Magento\Framework\ObjectManager\Config\Mapper\Dom->convert(Object(DOMDocument)) #3 /var/www/html/vendor/magento/framework/Config/Reader/Filesystem.php(132): Magento\Framework\Config\Reader\Filesystem->_readFiles(Object(Magento\Framework\Config\FileIterator)) #4 /var/www/html/vendor/magento/framework/App/ObjectManager/ConfigLoader.php(76): Magento\Framework\Config\Reader\Filesystem->read('global') #5 /var/www/html/vendor/magento/framework/App/ObjectManager/Environment/Deve in /var/www/html/vendor/magento/framework/Data/Argument/Interpreter/Constant.php on line 23

 /var/www/html/vendor/magento/framework/Data/Argument/Interpreter/Constant.php

The code 

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Framework\Data\Argument\Interpreter;

use Magento\Framework\Data\Argument\InterpreterInterface;

/**
 * Interpreter that returns value of a constant by its name
 */
class Constant implements InterpreterInterface
{
    /**
     * {@inheritdoc}
     * @return mixed
     * @throws \InvalidArgumentException
     */
    public function evaluate(array $data)
    {
        if (!isset($data['value']) || !defined($data['value'])) {
            throw new \InvalidArgumentException('Constant name is expected.');
        }
        return constant($data['value']);
    }
}

[BYK · Accepted solution]

Finally I solved this error.

Do like this from:

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Framework\Data\Argument\Interpreter;

use Magento\Framework\Data\Argument\InterpreterInterface;

/**
 * Interpreter that returns value of a constant by its name
 */
class Constant implements InterpreterInterface
{
    /**
     * {@inheritdoc}
     * @return mixed
     * @throws \InvalidArgumentException
     */
    public function evaluate(array $data)
    {
        if (!isset($data['value']) || !defined($data['value'])) {
            throw new \InvalidArgumentException('Constant name is expected.');
        }
        return constant($data['value']);
    }
}

To:

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Framework\Data\Argument\Interpreter;

use Magento\Framework\Data\Argument\InterpreterInterface;

/**
 * Interpreter that returns value of a constant by its name
 */
class Constant implements InterpreterInterface
{
    /**
     * {@inheritdoc}
     * @return mixed
     * @throws \InvalidArgumentException
     */
    public function evaluate(array $data)
    {
        if (!isset($data['value']) || !defined($data['value'])) {
            print_r($data);exit; 
            throw new \InvalidArgumentException('Constant name is expected.');
        }
        return constant($data['value']);
    }
}

You will notify from where you getting an error, now change it accordingly and re-fresh.

No I'm able to run the CLI commands and front-end also working fine.

[Leitonet]

In my case the error was a letter case issue in the path of the class that was holding the constant value.

On Windows the path works fine becasue folder names are "case insensitive", but then when I installed the module on Linux, the folder name was not found becase folder/file names are "case sentive" in this env.