async def _lock_parent_manifest_from_path(
self, path: FsPath
) -> AsyncIterator[Tuple[BaseLocalManifest, Optional[BaseLocalManifest]]]:
# This is the most complicated locking scenario.
# It requires locking the parent of the given entry and the entry itself
# if it exists.
# This is done in a two step process:
# - 1. Lock the parent (it must exist). While the parent is locked, no
# children can be added, renamed or removed.
# - 2. Lock the children if exists. It it doesn't, there is nothing to lock
# since the parent lock guarentees that it is not going to be added while
# using the context.
# This double locking is only required for a single use case: the overwriting
# of empty directory during a move. We have to make sure that no one adds
# something to the directory while it is being overwritten.
# If read/write locks were to be implemented, the parent would be write locked
# and the child read locked. This means that despite locking two entries, only
# a single entry is modified at a time.
# Source is root
if path.is_root():
raise FSPermissionError(filename=str(path))
# Loop over attempts
while True:
# Lock parent first
async with self._lock_manifest_from_path(path.parent) as parent:
# Parent is not a directory
if not is_folderish_manifest(parent):
raise FSNotADirectoryError(filename=path.parent)
# Child doesn't exist
if path.name not in parent.children:
yield parent, None
return
# Child exists
entry_id = parent.children[path.name]
try:
async with self.local_storage.lock_manifest(
entry_id) as manifest:
yield parent, manifest
return
# Child is not available
except FSLocalMissError as exc:
assert exc.id == entry_id
# Release the lock and download the child manifest
await self._load_manifest(entry_id)
async def entry_rename(self,
source: FsPath,
destination: FsPath,
overwrite: bool = True) -> Optional[EntryID]:
# Check write rights
self.check_write_rights(source)
# Source is root
if source.is_root():
raise FSPermissionError(filename=source)
# Destination is root
if destination.is_root():
raise FSPermissionError(filename=destination)
# Cross-directory renaming is not supported
if source.parent != destination.parent:
raise FSCrossDeviceError(filename=source, filename2=destination)
# Pre-fetch the source if necessary
if overwrite:
await self._get_manifest_from_path(source)
# Fetch and lock
async with self._lock_parent_manifest_from_path(destination) as (
parent, child):
# Source does not exist
if source.name not in parent.children:
raise FSFileNotFoundError(filename=source)
source_entry_id = parent.children[source.name]
# Source and destination are the same
if source.name == destination.name:
return None
# Destination already exists
if not overwrite and child is not None:
raise FSFileExistsError(filename=destination)
# Overwrite logic
if overwrite and child is not None:
source_manifest = await self._get_manifest(source_entry_id)
# Overwrite a file
if is_file_manifest(source_manifest):
# Destination is a folder
if is_folder_manifest(child):
raise FSIsADirectoryError(filename=destination)
# Overwrite a folder
if is_folder_manifest(source_manifest):
# Destination is not a folder
if is_file_manifest(child):
raise FSNotADirectoryError(filename=destination)
# Destination is not empty
if child.children:
raise FSDirectoryNotEmptyError(filename=destination)
# Create new manifest
new_parent = parent.evolve_children_and_mark_updated(
{
destination.name: source_entry_id,
source.name: None
},
pattern_filter=self.local_storage.get_pattern_filter(),
)
# Atomic change
await self.local_storage.set_manifest(parent.id, new_parent)
# Send event
self._send_event(ClientEvent.FS_ENTRY_UPDATED, id=parent.id)
# Return the entry id of the renamed entry
return parent.children[source.name]
def test_root(path, is_root):
obj = FsPath(path)
assert obj.is_root() is is_root
assert "//" not in str(obj)
