Magento – Magento 2: Running any command getting error Class Magento\Webapi\Model\Cache\Type\Web Api\Interceptor does not exist

The dataProvider class must be an existing class.

In your case you used PbuploadMediaGridDataProvider. I assumed that you based on development on what Magento does out of the box.

However, most of the time M2 uses a virtual type for the data provider classes.

I also assume that you want to use your Pinkblue\CatalogUpload\Model\ResourceModel\Media\Grid\Collection as the data provider.

To implement that you can add the following to your di.xml or create it :

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <virtualType name="PbuploadMediaGridCollectionFactoryForReporting" type="Magento\Framework\View\Element\UiComponent\DataProvider\CollectionFactory">
        <arguments>
            <argument name="collections" xsi:type="array">
                <item name="pbupload_media_listing_data_source" xsi:type="string">Pinkblue\CatalogUpload\Model\ResourceModel\Media\Grid\Collection</item>
            </argument>
        </arguments>
    </virtualType>

    <virtualType name="PbuploadMediaGridReporting" type="Magento\Framework\View\Element\UiComponent\DataProvider\Reporting">
        <arguments>
            <argument name="collectionFactory" xsi:type="object">PbuploadMediaGridCollectionFactoryForReporting</argument>
        </arguments>
    </virtualType>

    <virtualType name="PbuploadMediaGridDataProvider" type="Magento\Framework\View\Element\UiComponent\DataProvider\DataProvider">
        <arguments>
            <argument name="reporting" xsi:type="object">PbuploadMediaGridReporting</argument>
        </arguments>
    </virtualType>
</config>

I finally manage to resolve this issue. After digging into the Magento core, I found that in the \Magento\Framework\Reflection\ExtensionAttributeProcessor::buildOutputDataArray method, Magento get the type of the extension object attribute (in my case : Vendor\MultipleDiscounts\Api\Data\DiscountOrderItemInterface[]). If type is array, then Magento will substring the [] characters.

In my case the type was wrong : object Collection.

I use an observer to set my extension_attribute (sales order load after) and I have to change my code like this :

Before :

...
$orderExtension = $order->getExtensionAttributes();
if ($orderExtension == null) {
    $orderExtension = $this->orderExtensionFactory->create();
}
$discountOrderItems = $this->discountOrderItemRepository->getListByOrderId($order->getId());
$orderExtension->setDiscountsOrderItems($discountOrderItems);
...

After :

...
$orderExtension = $order->getExtensionAttributes();
if ($orderExtension == null) {
    $orderExtension = $this->orderExtensionFactory->create();
}
$discountOrderItems = $this->discountOrderItemRepository->getListByOrderId($order->getId());
$orderExtension->setDiscountsOrderItems($discountOrderItems->getItems());
...

I just add ->getItems() method on my $discountOrderItems collection object to return an array of object.

Hope this can help others.