Disabled flat: cast $attributeId as (int) in selects

app/code/Magento/Eav/Model/Entity/Collection/AbstractCollection.php

@@ -24,7 +24,7 @@
 abstract class AbstractCollection extends AbstractDb implements SourceProviderInterface
 {
     /**
-     * Attribute table alias prefix
+     * Define default prefix for attribute table alias
      */
     const ATTRIBUTE_TABLE_ALIAS_PREFIX = 'at_';
 
@@ -495,7 +495,7 @@ public function addAttributeToSelect($attribute, $joinType = false)
             $entity = clone $this->getEntity();
             $attributes = $entity->loadAllAttributes()->getAttributesByCode();
             foreach ($attributes as $attrCode => $attr) {
-                $this->_selectAttributes[$attrCode] = $attr->getId();
+                $this->_selectAttributes[$attrCode] = (int) $attr->getId();
             }
         } else {
             if (isset($this->_joinAttributes[$attribute])) {
@@ -511,7 +511,7 @@ public function addAttributeToSelect($attribute, $joinType = false)
                     )
                 );
             }
-            $this->_selectAttributes[$attrInstance->getAttributeCode()] = $attrInstance->getId();
+            $this->_selectAttributes[$attrInstance->getAttributeCode()] = (int) $attrInstance->getId();
         }
         return $this;
     }
@@ -1173,7 +1173,7 @@ public function _loadAttributes($printQuery = false, $logQuery = false)
             }
             $attribute = $this->_eavConfig->getAttribute($entity->getType(), $attributeCode);
             if ($attribute && !$attribute->isStatic()) {
-                $tableAttributes[$attribute->getBackendTable()][] = $attributeId;
+                $tableAttributes[$attribute->getBackendTable()][] = (int) $attributeId;
                 if (!isset($attributeTypes[$attribute->getBackendTable()])) {
                     $attributeTypes[$attribute->getBackendTable()] = $attribute->getBackendType();
                 }

app/code/Magento/Eav/Test/Unit/Model/Entity/Collection/AbstractCollectionStub.php

@@ -30,4 +30,14 @@ protected function _construct()
     {
         return $this->_init(\Magento\Framework\DataObject::class, 'test_entity_model');
     }
+
+    /**
+     * Retrieve collection empty item
+     *
+     * @return \Magento\Framework\DataObject
+     */
+    public function getNewEmptyItem()
+    {
+        return new \Magento\Framework\DataObject();
+    }
 }

app/code/Magento/Eav/Test/Unit/Model/Entity/Collection/AbstractCollectionTest.php

@@ -12,6 +12,10 @@
  */
 class AbstractCollectionTest extends \PHPUnit\Framework\TestCase
 {
+    const ATTRIBUTE_CODE = 'any_attribute';
+    const ATTRIBUTE_ID_STRING = '15';
+    const ATTRIBUTE_ID_INT = 15;
+
     /**
      * @var AbstractCollectionStub|\PHPUnit_Framework_MockObject_MockObject
      */
@@ -105,6 +109,26 @@ protected function setUp()
         $entityMock = $this->createMock(\Magento\Eav\Model\Entity\AbstractEntity::class);
         $entityMock->expects($this->any())->method('getConnection')->will($this->returnValue($connectionMock));
         $entityMock->expects($this->any())->method('getDefaultAttributes')->will($this->returnValue([]));
+        $entityMock->expects($this->any())->method('getLinkField')->willReturn('entity_id');
+
+        $attributeMock = $this->createMock(\Magento\Eav\Model\Attribute::class);
+        $attributeMock->expects($this->any())->method('isStatic')->willReturn(false);
+        $attributeMock->expects($this->any())->method('getAttributeCode')->willReturn(self::ATTRIBUTE_CODE);
+        $attributeMock->expects($this->any())->method('getBackendTable')->willReturn('eav_entity_int');
+        $attributeMock->expects($this->any())->method('getBackendType')->willReturn('int');
+        $attributeMock->expects($this->any())->method('getId')->willReturn(self::ATTRIBUTE_ID_STRING);
+
+        $entityMock
+            ->expects($this->any())
+            ->method('getAttribute')
+            ->with(self::ATTRIBUTE_CODE)
+            ->willReturn($attributeMock);
+
+        $this->configMock
+            ->expects($this->any())
+            ->method('getAttribute')
+            ->with(null, self::ATTRIBUTE_CODE)
+            ->willReturn($attributeMock);
 
         $this->validatorFactoryMock->expects(
             $this->any()
@@ -193,6 +217,30 @@ public function testRemoveItemByKey($values, $count)
         $this->assertNull($this->model->getItemById($testId));
     }
 
+    /**
+     * @dataProvider getItemsDataProvider
+     */
+    public function testAttributeIdIsInt($values)
+    {
+        $this->resourceHelperMock->expects($this->any())->method('getLoadAttributesSelectGroups')->willReturn([]);
+        $this->fetchStrategyMock->expects($this->any())->method('fetchAll')->will($this->returnValue($values));
+        $selectMock = $this->coreResourceMock->getConnection()->select();
+        $selectMock->expects($this->any())->method('from')->willReturn($selectMock);
+        $selectMock->expects($this->any())->method('join')->willReturn($selectMock);
+        $selectMock->expects($this->any())->method('where')->willReturn($selectMock);
+        $selectMock->expects($this->any())->method('columns')->willReturn($selectMock);
+
+        $this->model
+            ->addAttributeToSelect(self::ATTRIBUTE_CODE)
+            ->_loadEntities()
+            ->_loadAttributes();
+
+        $_selectAttributesActualValue = $this->readAttribute($this->model, '_selectAttributes');
+
+        $this->assertAttributeEquals([self::ATTRIBUTE_CODE => self::ATTRIBUTE_ID_STRING], '_selectAttributes', $this->model);
+        $this->assertSame($_selectAttributesActualValue[self::ATTRIBUTE_CODE], self::ATTRIBUTE_ID_INT);
+    }
+
     /**
      * @return array
      */