ENGCOM-3193: #14510: Creating custom customer attribute with default value 0 will cause not saving value for customer entity. #16915

Author: VladimirZaets

app/code/Magento/Catalog/Model/Product/Attribute/Backend/Boolean.php

@@ -25,7 +25,9 @@ public function beforeSave($object)
         $attributeCode = $this->getAttribute()->getName();
         if ($object->getData('use_config_' . $attributeCode)) {
             $object->setData($attributeCode, BooleanSource::VALUE_USE_CONFIG);
+            return $this;
         }
-        return $this;
+
+        return parent::beforeSave($object);
     }
 }

app/code/Magento/Downloadable/Setup/UpgradeData.php

@@ -0,0 +1,58 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Downloadable\Setup;
+
+use Magento\Eav\Setup\EavSetup;
+use Magento\Eav\Setup\EavSetupFactory;
+use Magento\Framework\Setup\ModuleDataSetupInterface;
+use Magento\Framework\Setup\UpgradeDataInterface;
+use Magento\Framework\Setup\ModuleContextInterface;
+
+/**
+ * @codeCoverageIgnore
+ */
+class UpgradeData implements UpgradeDataInterface
+{
+    /**
+     * EAV setup factory
+     *
+     * @var EavSetupFactory
+     */
+    private $eavSetupFactory;
+
+    /**
+     * Init
+     *
+     * @param EavSetupFactory $eavSetupFactory
+     */
+    public function __construct(EavSetupFactory $eavSetupFactory)
+    {
+        $this->eavSetupFactory = $eavSetupFactory;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function upgrade(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
+    {
+        $setup->startSetup();
+
+        if (version_compare($context->getVersion(), '2.0.3', '<')) {
+            /** @var EavSetup $eavSetup */
+            $eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);
+            // remove default value
+            $eavSetup->updateAttribute(
+                \Magento\Catalog\Model\Product::ENTITY,
+                'links_exist',
+                'default_value',
+                null
+            );
+        }
+
+        $setup->endSetup();
+    }
+}

app/code/Magento/Downloadable/etc/module.xml

@@ -6,7 +6,7 @@
  */
 -->
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
-    <module name="Magento_Downloadable" setup_version="2.0.2">
+    <module name="Magento_Downloadable" setup_version="2.0.3">
         <sequence>
             <module name="Magento_Catalog"/>
         </sequence>

app/code/Magento/Eav/Model/Entity/Attribute/AbstractAttribute.php

@@ -392,7 +392,7 @@ public function getIsVisibleOnFront()
     }
 
     /**
-     * @return string|int|bool|float
+     * @return string|null
      * @codeCoverageIgnore
      */
     public function getDefaultValue()

app/code/Magento/Eav/Model/Entity/Attribute/Backend/AbstractBackend.php

@@ -203,12 +203,12 @@ public function getEntityValueId($entity)
     /**
      * Retrieve default value
      *
-     * @return mixed
+     * @return string
      */
     public function getDefaultValue()
     {
         if ($this->_defaultValue === null) {
-            if ($this->getAttribute()->getDefaultValue()) {
+            if ($this->getAttribute()->getDefaultValue() !== null) {
                 $this->_defaultValue = $this->getAttribute()->getDefaultValue();
             } else {
                 $this->_defaultValue = "";
@@ -280,7 +280,7 @@ public function afterLoad($object)
     public function beforeSave($object)
     {
         $attrCode = $this->getAttribute()->getAttributeCode();
-        if (!$object->hasData($attrCode) && $this->getDefaultValue()) {
+        if (!$object->hasData($attrCode) && $this->getDefaultValue() !== '') {
             $object->setData($attrCode, $this->getDefaultValue());
         }