Incorrect partial attribute (EAV) reindex (Update by Schedule) for configurable product with childs visibility "Not Visible Individually"

[Nix-id]

Preconditions

1. Magento 2.2.1
2. PHP 7.1
3. MariaDB

Steps to reproduce

0. Create config product and childs
   For example with id '1', and his childs with '2','3'
1. set indexer method to "Update by Schedule"
2. Edit and save only Configurable product (don't edit childs)
3. waite while cron update MView
4. check DB catalog_product_index_eav. all entries with entity_id=1 and source_id in (2,3) are deleted. because of this, the filters on the catalog list page do not work correctly

Expected result

1. All index must be reindex correct

Actual result

Reson

In file
https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/Catalog/Model/Indexer/Product/Eav/AbstractAction.php
method
processRelations($indexer, $ids, $onlyParents = false)

if in $ids = only parent id then
$parentIds = $indexer->getRelationsByChild($ids);
return empty result
and
$childIds = $onlyParents ? [] : $indexer->getRelationsByParent($parentIds);
also empty

Fast solution

$parentIds = $indexer->getRelationsByChild($ids);

+$parentIds = array_unique(array_merge($parentIds, $ids));

$childIds = $onlyParents ? [] : $indexer->getRelationsByParent($parentIds);

[magento-engcom-team]

@Nix-id, thank you for your report.
We've created internal ticket(s) MAGETWO-85597 to track progress on the issue.

[okorshenko]

Hi @Nix-id
The issue has been fixed and delivered in 2.2-develop branch. Will be available with upcoming patch release.