ENGCOM-3449: Fix/add expresion.

Author: nmalevanec

dev/tests/integration/testsuite/Magento/Framework/Model/ResourceModel/Db/Collection/AbstractTest.php

@@ -72,4 +72,42 @@ public function testGetAllIdsWithBind()
         $this->_model->addBindParam('code', 'admin');
         $this->assertEquals(['0'], $this->_model->getAllIds());
     }
+
+    /**
+     * Check add field to select doesn't remove expression field from select.
+     *
+     * @return void
+     */
+    public function testAddExpressionFieldToSelectWithAdditionalFields()
+    {
+        $expectedColumns = ['code', 'test_field'];
+        $actualColumns = [];
+
+        $testExpression = new \Zend_Db_Expr('(sort_order + group_id)');
+        $this->_model->addExpressionFieldToSelect('test_field', $testExpression, ['sort_order', 'group_id']);
+        $this->_model->addFieldToSelect('code', 'code');
+        $columns = $this->_model->getSelect()->getPart(\Magento\Framework\DB\Select::COLUMNS);
+        foreach ($columns as $columnEntry) {
+            $actualColumns[] = $columnEntry[2];
+        }
+
+        $this->assertEquals($expectedColumns, $actualColumns);
+    }
+
+    /**
+     * Check add expression field doesn't remove all fields from select.
+     *
+     * @return void
+     */
+    public function testAddExpressionFieldToSelectWithoutAdditionalFields()
+    {
+        $expectedColumns = ['*', 'test_field'];
+
+        $testExpression = new \Zend_Db_Expr('(sort_order + group_id)');
+        $this->_model->addExpressionFieldToSelect('test_field', $testExpression, ['sort_order', 'group_id']);
+        $columns = $this->_model->getSelect()->getPart(\Magento\Framework\DB\Select::COLUMNS);
+        $actualColumns = [$columns[0][1], $columns[1][2]];
+
+        $this->assertEquals($expectedColumns, $actualColumns);
+    }
 }

lib/internal/Magento/Framework/Model/ResourceModel/Db/Collection/AbstractCollection.php

@@ -45,6 +45,13 @@ abstract class AbstractCollection extends AbstractDb implements SourceProviderIn
      */
     protected $_fieldsToSelect = null;
 
+    /**
+     * Expression fields to select in query.
+     *
+     * @var array
+     */
+    private $expressionFieldsToSelect = [];
+
     /**
      * Fields initial fields to select like id_field
      *
@@ -205,7 +212,7 @@ protected function _initSelectFields()
         $columnsToSelect = [];
         foreach ($columns as $columnEntry) {
             list($correlationName, $column, $alias) = $columnEntry;
-            if ($correlationName !== 'main_table') {
+            if ($correlationName !== 'main_table' || isset($this->expressionFieldsToSelect[$alias])) {
                 // Add joined fields to select
                 if ($column instanceof \Zend_Db_Expr) {
                     $column = $column->__toString();
@@ -346,9 +353,8 @@ public function addExpressionFieldToSelect($alias, $expression, $fields)
             $fullExpression = str_replace('{{' . $fieldKey . '}}', $fieldItem, $fullExpression);
         }
 
-        $fullExpression = new \Zend_Db_Expr($fullExpression);
-        $this->_fieldsToSelect[$alias] = $fullExpression;
-        $this->_fieldsToSelectChanged = true;
+        $this->getSelect()->columns([$alias => $fullExpression]);
+        $this->expressionFieldsToSelect[$alias] = $fullExpression;
 
         return $this;
     }

lib/internal/Magento/Framework/Model/Test/Unit/ResourceModel/Db/Collection/AbstractCollectionTest.php

@@ -269,9 +269,8 @@ public function addFieldToSelectDataProvider()
      */
     public function testAddExpressionFieldToSelect($alias, $expression, $fields, $expected)
     {
+        $this->selectMock->expects($this->once())->method('columns')->with($expected);
         $this->assertTrue($this->uut->addExpressionFieldToSelect($alias, $expression, $fields) instanceof Uut);
-        $this->assertEquals($expected, $this->uut->getFieldsToSelect());
-        $this->assertTrue($this->uut->wereFieldsToSelectChanged());
     }
 
     /**