Clear scroll context also when empty page was received (#1660)

Scroll contexts should always be cleared when they're not used
anymore. Retrieving an empty page from a scroll means it's finished
and the context can be cleared.

CHANGELOG.md

@@ -37,6 +37,7 @@ All notable changes to this project will be documented in this file based on the
 ### Improvements
 * Added `native_function_invocation` CS rule [#1606](https://github.com/ruflin/Elastica/pull/1606)
 * Elasticsearch test version changed from 6.5.2 to 6.6.1 [#1620](https://github.com/ruflin/Elastica/pull/1620)
+* Clear scroll context also when empty page was received [#1660](https://github.com/ruflin/Elastica/pull/1660)
 
 ### Deprecated
 

lib/Elastica/Scroll.php

@@ -85,6 +85,7 @@ public function next()
         } else {
             // If there are no pages left, we do not need to query ES.
             $this->clear();
+            $this->_currentResultSet = null;
         }
     }
 
@@ -147,7 +148,6 @@ public function clear()
 
             // Reset scroll ID so valid() returns false.
             $this->_nextScrollId = null;
-            $this->_currentResultSet = null;
         }
     }
 
@@ -164,7 +164,13 @@ protected function _setScrollId(ResultSet $resultSet)
 
         $this->_currentResultSet = $resultSet;
         ++$this->currentPage;
-        $this->_nextScrollId = $resultSet->getResponse()->isOk() && $resultSet->count() > 0 ? $resultSet->getResponse()->getScrollId() : null;
+        $this->_nextScrollId = null;
+        if ($resultSet->getResponse()->isOk()) {
+            $this->_nextScrollId = $resultSet->getResponse()->getScrollId();
+            if (0 === $resultSet->count()) {
+                $this->clear();
+            }
+        }
     }
 
     /**

test/Elastica/ScrollTest.php

@@ -95,6 +95,8 @@ public function testEmptyScroll()
 
         $this->assertEquals(0, $scroll->current()->count());
         $this->assertFalse($scroll->valid());
+
+        $this->_assertOpenSearchContexts($search->getClient(), 0);
     }
 
     /**