[DDC-1012] Implemented Expr isNull and isNotNull.

lib/Doctrine/ORM/Query/Expr.php

@@ -443,6 +443,28 @@ class Expr
         return new Expr\Func($x . ' NOT IN', (array) $y);
     }
 
+    /**
+     * Creates an IS NULL expression with the given arguments.
+     *
+     * @param string $x Field in string format to be restricted by IS NULL
+     * @return string
+     */
+    public function isNull($x)
+    {
+        return $x . ' IS NULL';
+    }
+
+    /**
+     * Creates an IS NOT NULL expression with the given arguments.
+     *
+     * @param string $x Field in string format to be restricted by IS NOT NULL
+     * @return string
+     */
+    public function isNotNull($x)
+    {
+        return $x . ' IS NOT NULL';
+    }
+
     /**
      * Creates a LIKE() comparison expression with the given arguments.
      *

tests/Doctrine/Tests/ORM/Query/ExprTest.php

@@ -256,6 +256,16 @@ class ExprTest extends \Doctrine\Tests\OrmTestCase
         $this->assertEquals('TRIM(u.id)', (string) $this->_expr->trim('u.id'));
     }
 
+    public function testIsNullExpr()
+    {
+        $this->assertEquals('u.id IS NULL', (string) $this->_expr->isNull('u.id'));
+    }
+
+    public function testIsNotNullExpr()
+    {
+        $this->assertEquals('u.id IS NOT NULL', (string) $this->_expr->isNotNull('u.id'));
+    }
+
     public function testInExpr()
     {
         $this->assertEquals('u.id IN(1, 2, 3)', (string) $this->_expr->in('u.id', array(1, 2, 3)));