The configuration parameter "componentType" is a required for "advanced_pricing_button" component. | Upgrade Magento 2.0.7 => 2.1.0

Had the same issue when migrating from Magento 2.0.7 to 2.1.0, the following WAR described on https://github.com/magento/magento2/issues/5236 fixed the problem for me:

In vendor/magento/module-configurable-product/Ui/DataProvider/Product/Form/Modifier/ConfigurablePrice.php look for the following code:

$meta[$groupCode]['children'][self::CODE_GROUP_PRICE] = array_replace_recursive(
    $meta[$groupCode]['children'][self::CODE_GROUP_PRICE],
    [
        'children' => [
            self::$advancedPricingButton => [
                'arguments' => [
                    'data' => [
                        'config' => $visibilityConfig,
                    ],
                ],
            ],
        ],
    ]
);

And replace the following line:

'config' => $visibilityConfig,

With:

'config' => ['componentType'=>'container',$visibilityConfig],

If you don't see any fields populated in your Magento product catalog BE then check some other products. In my case some products would show the following error:

Notice: Undefined offset: 118 in /......./vendor/magento/module-eav/Model/ResourceModel/ReadHandler.php on line 166

This happens because table catalog_product_entity_varchar contains an attribute which doesn't exist in other tables, in my case the problem went away by just removing the entries with the attribute_id listed in the error above:

mysql> delete from catalog_product_entity_varchar where attribute_id=XXXXXXX;
Query OK, 7890 rows affected (0.11 sec)

Make sure you back up your database before you start hacking away!