While working with the Magento 2 GraphQl it seems that the string translation does not work

I was with same problem. I’m building some modules to work with GraphQl and I have this problem. After search a lot and not found anything, I debugged Magento core to found the problem.

Magento 2 works with multiple areas, like you can see in vendor/magento/framework/App/Area.php

const AREA_GLOBAL = 'global';
const AREA_FRONTEND = 'frontend';
const AREA_ADMINHTML = 'adminhtml';
const AREA_DOC = 'doc';
const AREA_CRONTAB = 'crontab';
const AREA_WEBAPI_REST = 'webapi_rest';
const AREA_WEBAPI_SOAP = 'webapi_soap';
const AREA_GRAPHQL = 'graphql';

I’m debugged frontend area and found this in the file vendor/magento/framework/View/DesignLoader.php

public function load()
{
    $area = $this->_areaList->getArea($this->appState->getAreaCode());
    $area->load(MagentoFrameworkAppArea::PART_DESIGN);
    $area->load(MagentoFrameworkAppArea::PART_TRANSLATE);
    $area->detectDesign($this->_request);
}

To resolve my problem I’d create a plugin to load translate at the GraphQl area.

Steps:

1. Create a di.xml file under app/code/Vendor/Module/etc/graphql:

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="MagentoGraphQlControllerGraphQl">
        <plugin name="graphql_load_translate" type="VendorModulePluginControllerGraphQlPlugin" sortOrder="1" disabled="false"/>
    </type>
</config>

2. Create your plugin class under app/code/Vendor/Module/Plugin/Controller/GraphQlPlugin.php

    <?php

    namespace VendorModulePluginController;

    class GraphQlPlugin
    {
        /** @var MagentoFrameworkAppAreaList $areaList */
        private $areaList;

        /** @var MagentoFrameworkAppState $appState */
        private $appState;

        public function __construct(
            MagentoFrameworkAppAreaList $areaList,
            MagentoFrameworkAppState $appState
        )
        {
            $this->areaList = $areaList;
            $this->appState = $appState;
        }

        public function beforeDispatch(MagentoGraphQlControllerGraphQl $subject)
        {
            $area = $this->areaList->getArea($this->appState->getAreaCode());
            $area->load(MagentoFrameworkAppArea::PART_TRANSLATE);
        }
    }

3. Compile classes

php bin/magento setup:di:compile

This worked for me.