$stream_wrapper->getDirectoryPath() is used all over core, but is not defined in StreamWrapperInterface

I'm going to re-open this, the method is used in core requiring third party streamWrappers to implement even though it is not on interface.

modules/system/src/Routing/AssetRoutes.php:    $directory_path = $this->streamWrapperManager->getViaScheme('assets')->getDirectoryPath(); // @see 3504164
modules/image/src/Routing/ImageStyleRoutes.php:    $directory_path = $this->streamWrapperManager->getViaScheme('public')->getDirectoryPath();
modules/image/src/PathProcessor/PathProcessorImageStyles.php:    $directory_path = $this->streamWrapperManager->getViaScheme('public')->getDirectoryPath();
modules/image/src/Entity/ImageStyle.php:      $directory_path = $stream_wrapper_manager->getViaUri($uri)->getDirectoryPath();
lib/Drupal/Core/Updater/Updater.php:    return \Drupal::service('stream_wrapper_manager')->getViaScheme('temporary')->getDirectoryPath();
lib/Drupal/Core/File/FileSystem.php:      if ($filename = tempnam($wrapper->getDirectoryPath(), $prefix)) {
modules/package_manager/src/PathExcluder/SiteFilesExcluder.php:        $path = $wrapper->getDirectoryPath(); // This has a LocalStreams check, however that makes an assumption all replacment local streamWrappers will inherit from LocalStreams which is bad assumption.

Since not all streamWrappers will have a directoryPath my suggestion would instead to be that we remove the method from the public usage and find alternative solutions Core should not assume a streamWrapper path is local. This might create some initial pain, however longer term if we get into the mindset to not assume local disk access for anything expect local file paths we will be better aligned to the intended usage of streamWrappers.

Leaving as 'file system' for component as initial decisions need to come from there, eventually though this may need to expand to 'base system' or similar.

Providing an explicit link to 🐛 AssetRoutes::routes() assumes stream wrapper implements ::getDirectoryPath() Active which illustrates this well.

Could we start by looking at how we would change \Drupal\Core\File\FileSystem::tempnam() to not use ::getDirectoryPath()?

Do we need more strict type checks for LocalStream?

Could we start by looking at how we would change \Drupal\Core\File\FileSystem::tempnam() to not use ::getDirectoryPath()?

::realpath() of the scheme would accomplish the same outcome.

Do we need more strict type checks for LocalStream?

If using ::realpath() no, just validate the return is not FALSE. This allows classes that may implement local storage, however not extend LocalStream (such as extending a 3rd party framework to interface with core) to still function.

OK. I created an issue 📌 FileSystem::tempnam() should use realpath() instead of getDirectoryPath() Active so we can tackle that first.