README

Magento 2 supports custom source models for attributes except for indexing them into the catalog_product_index_eav table (which feeds layered navigation).

The original problem is found in \Magento\Catalog\Model\ResourceModel\Product\Indexer\Eav\Source:302 where it ensures that the values saved exist in the eav_attribute_option table. When using that custom source model, those values do not exist.

The first / easy solution is to comment out those lines. That doesn't work for production so a more durable method needs to be had. While using a preference is not preferrable, this will solve the problem in the short term.

After some research and many hours spent, I found that @maderlock has a good fix: magento/magento2#417 (comment)

Here is how to get this running:

• composer require fidesio/attribute-index-fix
• php bin/magento module:enable SwiftOtter_AttributeIndexFix
• php bin/magento cache:clean