MAGETWO-71136: Cannot save attribute in product page admin with a related conf product that has different attribute set sharing a multiselect attribute

Author: Stanislav Idolov

app/code/Magento/Eav/Model/Entity/AbstractEntity.php

@@ -455,24 +455,33 @@ public function getAttribute($attribute)
         return $attribute;
     }
 
+    /**
+     * Adding attribute to entity by scope.
+     *
+     * @param AbstractAttribute $attribute
+     * @param string $suffix
+     * @return $this
+     */
+    public function addAttributeByScope(AbstractAttribute $attribute, $suffix)
+    {
+        $attributeCode = $attribute->getAttributeCode();
+        $this->attributesByScope[$suffix][$attributeCode] = $attribute;
+        return $this->addAttribute($attribute);
+    }
+
     /**
      * Adding attribute to entity
      *
      * @param AbstractAttribute $attribute
-     * @param string|null $suffix
      * @return $this
      */
-    public function addAttribute(AbstractAttribute $attribute, $suffix = null)
+    public function addAttribute(AbstractAttribute $attribute)
     {
         $attribute->setEntity($this);
         $attributeCode = $attribute->getAttributeCode();
 
         $this->_attributesByCode[$attributeCode] = $attribute;
 
-        if ($suffix !== null) {
-            $this->attributesByScope[$suffix][$attributeCode] = $attribute;
-        }
-
         if ($attribute->isStatic()) {
             $this->_staticAttributes[$attributeCode] = $attribute;
         } else {

app/code/Magento/Eav/Model/Entity/AttributeLoader.php

@@ -70,7 +70,7 @@ public function loadAllAttributes(AbstractEntity $resource, DataObject $object =
         $attributes = $this->cache->getAttributes($typeCode, $suffix);
         if ($attributes) {
             foreach ($attributes as $attribute) {
-                $resource->addAttribute($attribute, $suffix);
+                $resource->addAttributeByScope($attribute, $suffix);
             }
             return $resource;
         }