test and docs to be clear about #4558

framework/base/Model.php

@@ -385,7 +385,6 @@ class Model extends Component implements IteratorAggregate, ArrayAccess, Arrayab
         if ($this->_validators === null) {
             $this->_validators = $this->createValidators();
         }
-
         return $this->_validators;
     }
 
@@ -404,7 +403,6 @@ class Model extends Component implements IteratorAggregate, ArrayAccess, Arrayab
                 $validators[] = $validator;
             }
         }
-
         return $validators;
     }
 
@@ -427,7 +425,6 @@ class Model extends Component implements IteratorAggregate, ArrayAccess, Arrayab
                 throw new InvalidConfigException('Invalid validation rule: a rule must specify both attribute names and validator type.');
             }
         }
-
         return $validators;
     }
 
@@ -436,6 +433,12 @@ class Model extends Component implements IteratorAggregate, ArrayAccess, Arrayab
      * This is determined by checking if the attribute is associated with a
      * [[\yii\validators\RequiredValidator|required]] validation rule in the
      * current [[scenario]].
+     *
+     * Note that when the validator has a conditional validation applied using
+     * [[\yii\validators\RequiredValidator::$when|$when]] this method will return
+     * `false` regardless of the `when` condition because it may be called be
+     * before the model is loaded with data.
+     *
      * @param string $attribute attribute name
      * @return boolean whether the attribute is required
      */
@@ -446,7 +449,6 @@ class Model extends Component implements IteratorAggregate, ArrayAccess, Arrayab
                 return true;
             }
         }
-
         return false;
     }
 
@@ -482,7 +484,6 @@ class Model extends Component implements IteratorAggregate, ArrayAccess, Arrayab
     public function getAttributeLabel($attribute)
     {
         $labels = $this->attributeLabels();
-
         return isset($labels[$attribute]) ? $labels[$attribute] : $this->generateAttributeLabel($attribute);
     }
 

tests/unit/data/base/Singer.php

@@ -10,6 +10,7 @@ class Singer extends Model
 {
     public $firstName;
     public $lastName;
+    public $test;
 
     public function rules()
     {
@@ -17,6 +18,7 @@ class Singer extends Model
             [['lastName'], 'default', 'value' => 'Lennon'],
             [['lastName'], 'required'],
             [['underscore_style'], 'yii\captcha\CaptchaValidator'],
+            [['test'], 'required', 'when' => function($model) { return $model->firstName === 'cebe'; }],
         ];
     }
 }

tests/unit/framework/base/ModelTest.php

@@ -216,7 +216,7 @@ class ModelTest extends TestCase
     public function testDefaultScenarios()
     {
         $singer = new Singer();
-        $this->assertEquals(['default' => ['lastName', 'underscore_style']], $singer->scenarios());
+        $this->assertEquals(['default' => ['lastName', 'underscore_style', 'test']], $singer->scenarios());
 
         $scenarios = [
             'default' => ['id', 'name', 'description'],
@@ -238,6 +238,13 @@ class ModelTest extends TestCase
         $singer = new Singer();
         $this->assertFalse($singer->isAttributeRequired('firstName'));
         $this->assertTrue($singer->isAttributeRequired('lastName'));
+
+        // attribute is not marked as required when a conditional validation is applied using `$when`.
+        // the condition should not be applied because this info may be retrieved before model is loaded with data
+        $singer->firstName = 'qiang';
+        $this->assertFalse($singer->isAttributeRequired('test'));
+        $singer->firstName = 'cebe';
+        $this->assertFalse($singer->isAttributeRequired('test'));
     }
 
     public function testCreateValidators()