<virtualType name="Magento\Framework\GraphQlSchemaStitching\Reader"
             type="Magento\Framework\GraphQlSchemaStitching\Common\Reader">
    <arguments>
        <argument name="readers" xsi:type="array">
            <item name="productDynamicAttributeReader"
                  xsi:type="object">
                Magento\CatalogGraphQl\Model\Config\AttributeReader
            </item>
            <item name="categoryDynamicAttributeReader"
                  xsi:type="object">
                Magento\CatalogGraphQl\Model\Config\CategoryAttributeReader
            </item>
            <item name="productSortDynamicAttributeReader"
                  xsi:type="object">
                Magento\CatalogGraphQl\Model\Config\SortAttributeReader
            </item>
            <item name="productFilterDynamicAttributeReader"
                  xsi:type="object">
                Magento\CatalogGraphQl\Model\Config\FilterAttributeReader
            </item>
        </argument>
    </arguments>
</virtualType>

This is a virtual type configuration.

This configuration is for the base area. Base area configurations will apply to all the sub-applications.

This virtualType configuration tells the Object Manager when a user wants a virtual Magento\Framework\GraphQlSchemaStitching\Reader object that it should return a Magento\Framework\GraphQlSchemaStitching\Common\Reader object.

This configuration tells the Object Manager that when a user wants a Magento\Framework\GraphQlSchemaStitching\Reader object that the following arguments should be used in the foo object's constructor.

• $readers = [...items...];

<virtualType name="Magento\Framework\GraphQlSchemaStitching\Reader"
             type="Magento\Framework\GraphQlSchemaStitching\Common\Reader">
    <arguments>
        <argument name="readers" xsi:type="array">
            <item name="graphql_reader" xsi:type="object">
                Magento\Framework\GraphQlSchemaStitching\GraphQlReader
            </item>
        </argument>
    </arguments>
</virtualType>

This is a virtual type configuration.

This configuration is for the base area. Base area configurations will apply to all the sub-applications.

This virtualType configuration tells the Object Manager when a user wants a virtual Magento\Framework\GraphQlSchemaStitching\Reader object that it should return a Magento\Framework\GraphQlSchemaStitching\Common\Reader object.

This configuration tells the Object Manager that when a user wants a Magento\Framework\GraphQlSchemaStitching\Reader object that the following arguments should be used in the foo object's constructor.

• $readers = [...items...];