fix: file size in cache is set back to zero if empty content is written to a non-empty file

Author: DeepDiver1975

changelog/unreleased/39016

@@ -0,0 +1,3 @@
+Bugfix: Update file size in cache after writing empty content to non-empty file
+
+https://github.com/owncloud/core/pull/39016

lib/private/Files/View.php

@@ -1234,7 +1234,7 @@ private function basicOperation($operation, $path, $hooks = [], $extraParam = nu
 					throw $e;
 				}
 
-				if ($result) {
+				if ($result !== false) {
 					if (\in_array('delete', $hooks)) {
 						$this->removeUpdate($storage, $internalPath);
 					}

tests/lib/Files/ViewTest.php

@@ -117,7 +117,7 @@ protected function tearDown(): void {
 		\OC_User::setUserId($this->user);
 		foreach ($this->storages as $storage) {
 			$cache = $storage->getCache();
-			$ids = $cache->getAll();
+			$cache->getAll();
 			$cache->clear();
 		}
 
@@ -1884,7 +1884,7 @@ function () use ($view, $lockedPath, &$lockTypeDuring, $operation) {
 					$lockTypeDuring = $this->getFileLockType($view, $lockedPath);
 
 					if ($operation === 'fopen') {
-						return \fopen('data://text/plain,test', 'r');
+						return \fopen('data://text/plain,test', 'rb');
 					}
 					return true;
 				}
@@ -2750,4 +2750,27 @@ public function testDeleteNonShareFolder($shareFolder, $deleteFolder) {
 		$view->mkdir($deleteFolder);
 		$this->assertTrue($view->rmdir($deleteFolder));
 	}
+
+	public function testCacheSizeUpdatedWhenEmptyingFile(): void {
+		$storage1 = $this->getTestStorage();
+		Filesystem::mount($storage1, [], '/');
+
+		$rootView = new View('');
+
+		# test with string as $data
+		$rootView->file_put_contents('welcome.txt', '1234567890');
+		$this->assertEquals(10, $rootView->filesize('welcome.txt'));
+
+		$rootView->file_put_contents('welcome.txt', '');
+		$this->assertEquals(0, $rootView->filesize('welcome.txt'));
+
+		# test with resource as $data
+		$stream = fopen('data://text/plain,1234567890', 'rb');
+		$rootView->file_put_contents('welcome.txt', $stream);
+		$this->assertEquals(10, $rootView->filesize('welcome.txt'));
+
+		$stream = fopen('data://text/plain,', 'rb');
+		$rootView->file_put_contents('welcome.txt', '');
+		$this->assertEquals(0, $rootView->filesize('welcome.txt'));
+	}
 }