[BUGFIX] Reset number of results in QueryResult after offset changes

Using offsetSet or unset allows manipulating the QueryResult manually.
As the result of `count` is cached, offset changes need to reset that
cache to accurately return the correct offset.

Resolves: #76310
Releases: master, 9.5
Change-Id: Ic43f3810766bdb1ee02800b07f6853c81ba404f5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63896
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>

typo3/sysext/extbase/Classes/Persistence/Generic/QueryResult.php

@@ -192,6 +192,7 @@ public function offsetGet($offset)
     public function offsetSet($offset, $value)
     {
         $this->initialize();
+        $this->numberOfResults = null;
         $this->queryResult[$offset] = $value;
     }
 
@@ -204,6 +205,7 @@ public function offsetSet($offset, $value)
     public function offsetUnset($offset)
     {
         $this->initialize();
+        $this->numberOfResults = null;
         unset($this->queryResult[$offset]);
     }
 

typo3/sysext/extbase/Tests/Unit/Persistence/Generic/QueryResultTest.php

@@ -158,6 +158,24 @@ public function countOnlyCallsGetObjectCountByQueryOnPersistenceManagerOnce()
         $this->assertEquals(2, $this->queryResult->count());
     }
 
+    /**
+     * @test
+     */
+    public function countCallsGetObjectCountByQueryIfOffsetChanges()
+    {
+        $this->mockPersistenceManager->expects(self::once())->method('getObjectCountByQuery')->willReturn(2);
+        $firstCount = $this->queryResult->count();
+        $this->queryResult->offsetSet(3, new \stdClass());
+        $this->queryResult->offsetSet(4, new \stdClass());
+        $secondCount = $this->queryResult->count();
+        $this->queryResult->offsetUnset(1);
+        $thirdCount = $this->queryResult->count();
+
+        self::assertSame(2, $firstCount);
+        self::assertSame(4, $secondCount);
+        self::assertSame(3, $thirdCount);
+    }
+
     /**
      * @test
      */