Magento 2.1 Multi Select Attribute doesn't save empty values

[Corefix]

Preconditions

1. Magento 2.1
2. Chrome 52.x

Steps to reproduce

1. Go to Magento admin
2. Go to Products > Catalog
3. Select a product that have a multi select attribute
4. Find the multi select attribute and set one or more of the options on the product (so it looks like the following image).
   
5. Save the product
6. Go back and edit the same product again.
7. Now deselect all options in the same multi select field
8. Save product again

Expected result

1. The product should now have no options selected

Actual result

1. Product have all options still selected.

It looks like the empty fields are not included in the post request, which they should, since removing values is just as important as setting them :-)

[sevos1984]

This is a known issue, internal ticket id MAGETWO-57226. Thanks for posting

[developer-lindner]

@Corefix Update to 2.1.1. and report back or close this ticket otherwise.

[nagno]

It still not works in 2.1.1. I will create a ticket on the partner portal as well. (hopefully it will get more priority)

[TClilMouse]

Still not works in 2.1.3

[nagno]

@seavenger this patch works for me: #6899

[roseofgold]

patch didn't work for me on 2.1.2

[nagno]

@roseofgold
are you sure you applied it correctly?
We are using it in a production system without any issues.

[roseofgold]

@nagno No I'm not sure. I just tried applying it again and now I can't use my admin :(

[nagno]

@roseofgold your issue is probably not related to this patch or you have an interfering customisation.
If you check the comments on the patch, @wigman created a 2.1.3 compatible version as well.

[roseofgold]

@nagno thought you might like to know (and for posterity) that it works for me in IE11 but not in Chrome (v55). It's probably some customization that causing problems as it works differently in different browsers.

[nagno]

@roseofgold It is not working for us in any browser (even in a Vanilla Magento environment). It is still not working in 2.1.5.

Progress so far: we got one not working patch from the support team and another one, which was breaking the attribute set change functionality (you wasn't able to select an attribute set for new products as well).

[roseofgold]

@nagno Updating to 2.1.6 broke it all browsers and all environments. I believe this issue should not be closed.

[nkajic]

Seems like duplicate of #6253 #7687 #4545
and that this is fixed by
https://github.com/nagno/magento2/commit/b380502570b92449326ab6ed50e6ce0359287240

[hoektoe]

Still experiencing this issue in 2.1.4

[magento-engcom-team]

@Corefix, thank you for your report.
We were not able to reproduce this issue by following the steps you provided. If you'd like to update it, please reopen the issue.
We tested the issue on 2.3.0-dev, 2.2.0, 2.1.9

[nagno]

Of course you are not able to reproduce it, because it was fixed in 2.1.8. (See changelog for 2.1.8)
I did report it in October 2016 via the partner portal and after 2 not working patches Magento finally fixed it. It took about 9 months to provide it even with "priority" partner portal support...

[WilliamChongSDG]

This issue still persist in Magento ver. 2.2.2

[A-1A]

I Found Solution after R&D On Magento database.
Login In your phpmyadmin
Go to your website database
Open "eav_attribute" table
Find Your multiselect "attribute_id"
Edit Row
If "backend_model" Column blank then paste this Magento\Eav\Model\Entity\Attribute\Backend\ArrayBackend
And Also Please check this
https://magento.stackexchange.com/questions/224621/warning-array-filter-expects-parameter-1-to-be-array/230444#230444

[yohanespradono]

this happens in our v2.1.9 intermittently eventhough the attributes have Magento\Eav\Model\Entity\Attribute\Backend\ArrayBackend in its "backend_model" column.

When saving a product, some attributes have ->getAttributeSetInfo() returns null and some others return an empty array. This causes \Magento\Eav\Model\Entity\Attribute\AbstractAttribute::isInSet($setId) to return different values regarding whether getAttributeSetInfo is null or an empty array.

And later it causes function in \Magento\Eav\Model\Entity\AbstractEntity::_isApplicableAttribute() to return differently for each attribute. then it causes the foreach in \Magento\Eav\Model\Entity\AbstractEntity::walkAttributes to skip calling call_user_func_array on some attributes when those attributes have getAttributeSetInfo return empty array.

I am proposing this patch

in function \Magento\Framework\DataObject::__call
replace

            case 'has':
                $key = $this->_underscore(substr($method, 3));
                return isset($this->_data[$key]);

with

            case 'has':
                $key = $this->_underscore(substr($method, 3));
                return isset($this->_data[$key]) and !empty($this->_data[$key]);

or

in function \Magento\Eav\Model\Entity\Attribute\Set::addSetInfo($entityType, array $attributes, $setId = null)
replace

                    if (!is_array($attributeSetInfo)) {
                        $attributeSetInfo = [];
                    }

with

                    if (!is_array($attributeSetInfo)) {
                        $attributeSetInfo = null;
                    }