Add isNotNull to ExpressionBuilder (#408)

Add isNotNull() in ExpressionBuilder

Co-authored-by: Alexander M. Turek <me@derrabus.de>
Co-authored-by: Grégoire Paris <postmaster@greg0ire.fr>

docs/en/expression-builder.rst

@@ -124,6 +124,16 @@ isNull
 
     $collection->matching(new Criteria($expression));
 
+isNotNull
+---------
+
+.. code-block:: php
+    $expressionBuilder = Criteria::expr();
+
+    $expression = $expressionBuilder->isNotNull('foo');
+
+    $collection->matching(new Criteria($expression));
+
 in
 ---
 

src/ExpressionBuilder.php

@@ -77,6 +77,11 @@ public function isNull(string $field)
         return new Comparison($field, Comparison::EQ, new Value(null));
     }
 
+    public function isNotNull(string $field): Comparison
+    {
+        return new Comparison($field, Comparison::NEQ, new Value(null));
+    }
+
     /**
      * @param mixed[] $values
      *

tests/ExpressionBuilderTest.php

@@ -114,6 +114,14 @@ public function testIsNull(): void
         self::assertEquals(Comparison::EQ, $expr->getOperator());
     }
 
+    public function testIsNotNull(): void
+    {
+        $expr = $this->builder->isNotNull('a');
+
+        self::assertInstanceOf(Comparison::class, $expr);
+        self::assertEquals(Comparison::NEQ, $expr->getOperator());
+    }
+
     public function testContains(): void
     {
         $expr = $this->builder->contains('a', 'b');