Bugfix/20002 superfluous query on head request in serializer

framework/rest/Serializer.php

@@ -189,6 +189,7 @@
     protected function serializeDataProvider($dataProvider)
     {
         if (($pagination = $dataProvider->getPagination()) !== false) {
+            $pagination->totalCount = $dataProvider->getTotalCount();
             $this->addPaginationHeaders($pagination);
         }
         if ($this->request->getIsHead()) {

tests/framework/rest/SerializerTest.php

@@ -439,6 +439,30 @@ public function testHeadSerializeDataProvider($dataProvider, $expectedResult, $s
         ]);
         $serializer->preserveKeys = $saveKeys;
         $this->assertEmpty($serializer->serialize($dataProvider));
+        $this->assertNotEmpty($serializer->response->getHeaders()->get($serializer->totalCountHeader));
+
+        $arrayDataProviderMock = $this->getMockBuilder(ArrayDataProvider::className())
+        ->disableOriginalConstructor()
+        ->getMock();
+
+        // stub getModels to prevent empty
+        $arrayDataProviderMock
+        ->method('getModels')
+        ->willReturn($expectedResult);
+
+        // stub getPagination for header
+        $arrayDataProviderMock
+        ->method('getPagination')
+        ->willReturn($dataProvider->getPagination());
+
+        // assert normal HEAD is empty response
+        $this->assertEmpty($serializer->serialize($arrayDataProviderMock));
+
+        // Test #20002:  Set up the expectation for the getModels method
+        $arrayDataProviderMock->expects($this->never())
+            ->method('getModels');
+
+        // reset Method
         unset($_POST[$request->methodParam], $_SERVER['REQUEST_METHOD']);
     }