Added `QueryInterface::emulateExecution()`

Added `QueryInterface::emulateExecution()`, which allows preventing of
the actual query execution.
This allows to cancel `DataProvider` preventing search query execution
in case search model is invalid:

``` php
public function search($params)
    {
        $query = Item::find();

        $dataProvider = new ActiveDataProvider([
            'query' => $query,
        ]);

        $this->load($params);

        if (!$this->validate()) {
            $query->where('0=1');
            $query->emulateExecution(); // No SQL execution will be done
            return $dataProvider;
        }
```

This also fix unecessary query in case of `via()` usage. See #12390.

fixes #12390
fixes #6373
close #12708

framework/CHANGELOG.md

@@ -28,7 +28,8 @@ Yii Framework 2 Change Log
 - Bug #13089: Fixed `yii\console\controllers\AssetController::adjustCssUrl()` breaks URL reference specification (`url(#id)`) (vitalyzhakov)
 - Bug #7727: Fixed truncateHtml leaving extra tags (developeruz)
 - Bug #13118: Fixed `handleAction()` function in `yii.js` to handle attribute `data-pjax=0` as disabled PJAX (silverfire)
-- Enh #6809: Added `\yii\caching\Cache::$defaultDuration` property, allowing to set custom default cache duration (sdkiller)
+- Enh #6373: Introduce `yii\db\Query::emulateExecution()` to force returning an empty result for a query (klimov-paul)
+- Enh #6809: Added `yii\caching\Cache::$defaultDuration` property, allowing to set custom default cache duration (sdkiller)
 - Enh #7333: Improved error message for `yii\di\Instance::ensure()` when a component does not exist (cebe)
 - Enh #7420: Attributes for prompt generated with `renderSelectOptions` of `\yii\helpers\Html` helper (arogachev)
 - Enh #9162: Added support of closures in `value` for attributes in `yii\widgets\DetailView` (arogachev)
@@ -37,6 +38,7 @@ Yii Framework 2 Change Log
 - Enh #11756: Added type mapping for `varbinary` data type in MySQL DBMS (silverfire)
 - Enh #11929: Changed `type` column type from `int` to `smallInt` in RBAC migrations (silverfire)
 - Enh #12015: Changed visibility `yii\db\ActiveQueryTrait::createModels()` from private to protected (ArekX, dynasource)
+- Enh #12390: Avoid creating queries with false where contdition (`0=1`) when fetching relational data (klimov-paul)
 - Enh #12619: Added catch `Throwable` in `yii\base\ErrorHandler::handleException()` (rob006)
 - Enh #12726: `yii\base\Application::$version` converted to `yii\base\Module::$version` virtual property, allowing to specify version as a PHP callback (klimov-paul)
 - Enh #12738: Added support for creating protocol-relative URLs in `UrlManager::createAbsoluteUrl()` and `Url` helper methods (rob006)
@@ -53,7 +55,7 @@ Yii Framework 2 Change Log
 - Enh #13036: Added shortcut methods `asJson()` and `asXml()` for returning JSON and XML data in web controller actions (cebe)
 - Enh #13020: Added `disabledListItemSubTagOptions` attribute for `yii\widgets\LinkPager` in order to customize the disabled list item sub tag element (nadar)
 - Enh #12988: Changed `textarea` method within the `yii\helpers\BaseHtml` class to allow users to control whether html entities found within `$value` will be double-encoded or not (cyphix333)
-- Enh #13074: Improved `\yii\log\SyslogTarget` with `$options` to be able to change the default `openlog` options. (timbeks)
+- Enh #13074: Improved `yii\log\SyslogTarget` with `$options` to be able to change the default `openlog` options. (timbeks)
 - Enh #13050: Added `yii\filters\HostControl` allowing protection against 'host header' attacks (klimov-paul)
 - Enh: Added constants for specifying `yii\validators\CompareValidator::$type` (cebe)
 - Enh #12854: Added `RangeNotSatisfiableHttpException` to cover HTTP error 416 file request exceptions (zalatov)

framework/UPGRADE.md

@@ -50,6 +50,12 @@ if you want to upgrade from version A to version C and there is
 version B between A and C, you need to follow the instructions
 for both A and B.
 
+Upgrade from Yii 2.0.10
+-----------------------
+
+* A new method `public function emulateExecution($value = true);` has been added to the `yii\db\QueryInterace`.
+  This method is implemented in the `yii\db\QueryTrait`, so this only affects your code if you implement QueryInterface
+  in a class that does not use the trait.
 
 Upgrade from Yii 2.0.9
 ----------------------

framework/db/ActiveRelationTrait.php

@@ -464,6 +464,9 @@ trait ActiveRelationTrait
                     }
                 }
             }
+            if (empty($values)) {
+                $this->emulateExecution();
+            }
         } else {
             // composite keys
 
@@ -478,6 +481,9 @@ trait ActiveRelationTrait
                     $v[$attribute] = $model[$link];
                 }
                 $values[] = $v;
+                if (empty($v)) {
+                    $this->emulateExecution();
+                }
             }
         }
         $this->andWhere(['in', $attributes, array_unique($values, SORT_REGULAR)]);

framework/db/Query.php

@@ -207,6 +207,9 @@ class Query extends Component implements QueryInterface
      */
     public function all($db = null)
     {
+        if ($this->emulateExecution) {
+            return [];
+        }
         $rows = $this->createCommand($db)->queryAll();
         return $this->populate($rows);
     }
@@ -244,6 +247,9 @@ class Query extends Component implements QueryInterface
      */
     public function one($db = null)
     {
+        if ($this->emulateExecution) {
+            return false;
+        }
         return $this->createCommand($db)->queryOne();
     }
 
@@ -257,6 +263,9 @@ class Query extends Component implements QueryInterface
      */
     public function scalar($db = null)
     {
+        if ($this->emulateExecution) {
+            return null;
+        }
         return $this->createCommand($db)->queryScalar();
     }
 
@@ -268,6 +277,10 @@ class Query extends Component implements QueryInterface
      */
     public function column($db = null)
     {
+        if ($this->emulateExecution) {
+            return [];
+        }
+
         if ($this->indexBy === null) {
             return $this->createCommand($db)->queryColumn();
         }
@@ -300,6 +313,9 @@ class Query extends Component implements QueryInterface
      */
     public function count($q = '*', $db = null)
     {
+        if ($this->emulateExecution) {
+            return 0;
+        }
         return $this->queryScalar("COUNT($q)", $db);
     }
 
@@ -313,6 +329,9 @@ class Query extends Component implements QueryInterface
      */
     public function sum($q, $db = null)
     {
+        if ($this->emulateExecution) {
+            return 0;
+        }
         return $this->queryScalar("SUM($q)", $db);
     }
 
@@ -326,6 +345,9 @@ class Query extends Component implements QueryInterface
      */
     public function average($q, $db = null)
     {
+        if ($this->emulateExecution) {
+            return 0;
+        }
         return $this->queryScalar("AVG($q)", $db);
     }
 
@@ -363,6 +385,9 @@ class Query extends Component implements QueryInterface
      */
     public function exists($db = null)
     {
+        if ($this->emulateExecution) {
+            return false;
+        }
         $command = $this->createCommand($db);
         $params = $command->params;
         $command->setSql($command->db->getQueryBuilder()->selectExists($command->getSql()));
@@ -379,6 +404,10 @@ class Query extends Component implements QueryInterface
      */
     protected function queryScalar($selectExpression, $db)
     {
+        if ($this->emulateExecution) {
+            return null;
+        }
+
         $select = $this->select;
         $limit = $this->limit;
         $offset = $this->offset;

framework/db/QueryInterface.php

@@ -252,4 +252,16 @@ interface QueryInterface
      * @return $this the query object itself
      */
     public function offset($offset);
+
+    /**
+     * Sets whether to emulate query execution, preventing any interaction with data storage.
+     * After this mode is enabled, methods, returning query results like [[one()]], [[all()]], [[exists()]]
+     * and so on, will return empty or false values.
+     * You should use this method in case your program logic indicates query should not return any results, like
+     * in case you set false where condition like `0=1`.
+     * @param boolean $value whether to prevent query execution.
+     * @return $this the query object itself.
+     * @since 2.0.11
+     */
+    public function emulateExecution($value = true);
 }

framework/db/QueryTrait.php

@@ -50,6 +50,12 @@ trait QueryTrait
      * row data. For more details, see [[indexBy()]]. This property is only used by [[QueryInterface::all()|all()]].
      */
     public $indexBy;
+    /**
+     * @var boolean whether to emulate the actual query execution, returning empty or false results.
+     * @see emulateExecution()
+     * @since 2.0.11
+     */
+    public $emulateExecution = false;
 
 
     /**
@@ -388,4 +394,20 @@ trait QueryTrait
         $this->offset = $offset;
         return $this;
     }
+
+    /**
+     * Sets whether to emulate query execution, preventing any interaction with data storage.
+     * After this mode is enabled, methods, returning query results like [[one()]], [[all()]], [[exists()]]
+     * and so on, will return empty or false values.
+     * You should use this method in case your program logic indicates query should not return any results, like
+     * in case you set false where condition like `0=1`.
+     * @param boolean $value whether to prevent query execution.
+     * @return $this the query object itself.
+     * @since 2.0.11
+     */
+    public function emulateExecution($value = true)
+    {
+        $this->emulateExecution = $value;
+        return $this;
+    }
 }

tests/framework/db/ActiveRecordTest.php

@@ -1294,4 +1294,70 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         $this->assertEquals($newTotal, $newOrder->total);
     }
 
+    public function testEmulateExecution()
+    {
+        $this->assertGreaterThan(0, Customer::find()->from('customer')->count());
+
+        $rows = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->all();
+        $this->assertSame([], $rows);
+
+        $row = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->one();
+        $this->assertSame(null, $row);
+
+        $exists = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->exists();
+        $this->assertSame(false, $exists);
+
+        $count = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->count();
+        $this->assertSame(0, $count);
+
+        $sum = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->sum('id');
+        $this->assertSame(0, $sum);
+
+        $sum = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->average('id');
+        $this->assertSame(0, $sum);
+
+        $max = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->max('id');
+        $this->assertSame(null, $max);
+
+        $min = Customer::find()
+            ->from('customer')
+            ->emulateExecution()
+            ->min('id');
+        $this->assertSame(null, $min);
+
+        $scalar = Customer::find()
+            ->select(['id'])
+            ->from('customer')
+            ->emulateExecution()
+            ->scalar();
+        $this->assertSame(null, $scalar);
+
+        $column = Customer::find()
+            ->select(['id'])
+            ->from('customer')
+            ->emulateExecution()
+            ->column();
+        $this->assertSame([], $column);
+    }
 }

tests/framework/db/QueryTest.php

@@ -2,6 +2,7 @@
 
 namespace yiiunit\framework\db;
 
+use yii\db\Connection;
 use yii\db\Expression;
 use yii\db\Query;
 
@@ -317,4 +318,73 @@ abstract class QueryTest extends DatabaseTestCase
         $count = (new Query)->from('customer')->having(['status' => 2])->count('*', $db);
         $this->assertEquals(1, $count);
     }
+
+    public function testEmulateExecution()
+    {
+        $db = $this->getConnection();
+
+        $this->assertGreaterThan(0, (new Query())->from('customer')->count('*', $db));
+
+        $rows = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->all($db);
+        $this->assertSame([], $rows);
+
+        $row = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->one($db);
+        $this->assertSame(false, $row);
+
+        $exists = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->exists($db);
+        $this->assertSame(false, $exists);
+
+        $count = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->count('*', $db);
+        $this->assertSame(0, $count);
+
+        $sum = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->sum('id', $db);
+        $this->assertSame(0, $sum);
+
+        $sum = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->average('id', $db);
+        $this->assertSame(0, $sum);
+
+        $max = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->max('id', $db);
+        $this->assertSame(null, $max);
+
+        $min = (new Query())
+            ->from('customer')
+            ->emulateExecution()
+            ->min('id', $db);
+        $this->assertSame(null, $min);
+
+        $scalar = (new Query())
+            ->select(['id'])
+            ->from('customer')
+            ->emulateExecution()
+            ->scalar($db);
+        $this->assertSame(null, $scalar);
+
+        $column = (new Query())
+            ->select(['id'])
+            ->from('customer')
+            ->emulateExecution()
+            ->column($db);
+        $this->assertSame([], $column);
+    }
 }