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GH-127807: pathlib ABCs: move private copying methods to dedicated class (#127810)
Move 9 private `PathBase` attributes and methods into a new `CopyWorker` class. Change `PathBase.copy` from a method to a `CopyWorker` instance. The methods remain private in the `CopyWorker` class. In future we might make some/all of them public so that user subclasses of `PathBase` can customize the copying process (in particular reading/writing of metadata,) but we'd need to make `PathBase` public first.
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Barney Gale
GitHub
parent
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commit
8d9f52a7be
3 changed files with 261 additions and 248 deletions
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@ -57,6 +57,132 @@ class PathGlobber(_GlobberBase):
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return path.with_segments(str(path) + text)
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class CopyWorker:
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"""
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Class that implements copying between path objects. An instance of this
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class is available from the PathBase.copy property; it's made callable so
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that PathBase.copy() can be treated as a method.
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The target path's CopyWorker drives the process from its _create() method.
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Files and directories are exchanged by calling methods on the source and
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target paths, and metadata is exchanged by calling
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source.copy._read_metadata() and target.copy._write_metadata().
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"""
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__slots__ = ('_path',)
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def __init__(self, path):
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self._path = path
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def __call__(self, target, follow_symlinks=True, dirs_exist_ok=False,
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preserve_metadata=False):
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"""
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Recursively copy this file or directory tree to the given destination.
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"""
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if not isinstance(target, PathBase):
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target = self._path.with_segments(target)
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# Delegate to the target path's CopyWorker object.
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return target.copy._create(self._path, follow_symlinks, dirs_exist_ok, preserve_metadata)
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_readable_metakeys = frozenset()
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def _read_metadata(self, metakeys, *, follow_symlinks=True):
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"""
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Returns path metadata as a dict with string keys.
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"""
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raise NotImplementedError
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_writable_metakeys = frozenset()
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def _write_metadata(self, metadata, *, follow_symlinks=True):
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"""
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Sets path metadata from the given dict with string keys.
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"""
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raise NotImplementedError
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def _create(self, source, follow_symlinks, dirs_exist_ok, preserve_metadata):
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self._ensure_distinct_path(source)
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if preserve_metadata:
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metakeys = self._writable_metakeys & source.copy._readable_metakeys
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else:
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metakeys = None
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if not follow_symlinks and source.is_symlink():
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self._create_symlink(source, metakeys)
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elif source.is_dir():
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self._create_dir(source, metakeys, follow_symlinks, dirs_exist_ok)
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else:
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self._create_file(source, metakeys)
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return self._path
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def _create_dir(self, source, metakeys, follow_symlinks, dirs_exist_ok):
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"""Copy the given directory to our path."""
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children = list(source.iterdir())
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self._path.mkdir(exist_ok=dirs_exist_ok)
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for src in children:
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dst = self._path.joinpath(src.name)
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if not follow_symlinks and src.is_symlink():
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dst.copy._create_symlink(src, metakeys)
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elif src.is_dir():
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dst.copy._create_dir(src, metakeys, follow_symlinks, dirs_exist_ok)
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else:
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dst.copy._create_file(src, metakeys)
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if metakeys:
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metadata = source.copy._read_metadata(metakeys)
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if metadata:
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self._write_metadata(metadata)
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def _create_file(self, source, metakeys):
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"""Copy the given file to our path."""
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self._ensure_different_file(source)
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with source.open('rb') as source_f:
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try:
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with self._path.open('wb') as target_f:
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copyfileobj(source_f, target_f)
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except IsADirectoryError as e:
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if not self._path.exists():
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# Raise a less confusing exception.
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raise FileNotFoundError(
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f'Directory does not exist: {self._path}') from e
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raise
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if metakeys:
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metadata = source.copy._read_metadata(metakeys)
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if metadata:
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self._write_metadata(metadata)
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def _create_symlink(self, source, metakeys):
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"""Copy the given symbolic link to our path."""
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self._path.symlink_to(source.readlink())
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if metakeys:
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metadata = source.copy._read_metadata(metakeys, follow_symlinks=False)
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if metadata:
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self._write_metadata(metadata, follow_symlinks=False)
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def _ensure_different_file(self, source):
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"""
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Raise OSError(EINVAL) if both paths refer to the same file.
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"""
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pass
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def _ensure_distinct_path(self, source):
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"""
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Raise OSError(EINVAL) if the other path is within this path.
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"""
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# Note: there is no straightforward, foolproof algorithm to determine
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# if one directory is within another (a particularly perverse example
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# would be a single network share mounted in one location via NFS, and
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# in another location via CIFS), so we simply checks whether the
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# other path is lexically equal to, or within, this path.
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if source == self._path:
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err = OSError(EINVAL, "Source and target are the same path")
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elif source in self._path.parents:
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err = OSError(EINVAL, "Source path is a parent of target path")
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else:
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return
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err.filename = str(source)
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err.filename2 = str(self._path)
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raise err
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class PurePathBase:
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"""Base class for pure path objects.
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@ -374,31 +500,6 @@ class PathBase(PurePathBase):
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except (OSError, ValueError):
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return False
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def _ensure_different_file(self, other_path):
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"""
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Raise OSError(EINVAL) if both paths refer to the same file.
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"""
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pass
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def _ensure_distinct_path(self, other_path):
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"""
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Raise OSError(EINVAL) if the other path is within this path.
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"""
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# Note: there is no straightforward, foolproof algorithm to determine
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# if one directory is within another (a particularly perverse example
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# would be a single network share mounted in one location via NFS, and
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# in another location via CIFS), so we simply checks whether the
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# other path is lexically equal to, or within, this path.
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if self == other_path:
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err = OSError(EINVAL, "Source and target are the same path")
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elif self in other_path.parents:
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err = OSError(EINVAL, "Source path is a parent of target path")
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else:
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return
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err.filename = str(self)
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err.filename2 = str(other_path)
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raise err
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def open(self, mode='r', buffering=-1, encoding=None,
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errors=None, newline=None):
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"""
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@ -537,88 +638,13 @@ class PathBase(PurePathBase):
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"""
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raise NotImplementedError
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def _symlink_to_target_of(self, link):
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"""
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Make this path a symlink with the same target as the given link. This
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is used by copy().
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"""
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self.symlink_to(link.readlink())
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def mkdir(self, mode=0o777, parents=False, exist_ok=False):
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"""
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Create a new directory at this given path.
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"""
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raise NotImplementedError
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# Metadata keys supported by this path type.
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_readable_metadata = _writable_metadata = frozenset()
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def _read_metadata(self, keys=None, *, follow_symlinks=True):
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"""
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Returns path metadata as a dict with string keys.
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"""
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raise NotImplementedError
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def _write_metadata(self, metadata, *, follow_symlinks=True):
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"""
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Sets path metadata from the given dict with string keys.
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"""
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raise NotImplementedError
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def _copy_metadata(self, target, *, follow_symlinks=True):
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"""
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Copies metadata (permissions, timestamps, etc) from this path to target.
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"""
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# Metadata types supported by both source and target.
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keys = self._readable_metadata & target._writable_metadata
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if keys:
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metadata = self._read_metadata(keys, follow_symlinks=follow_symlinks)
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target._write_metadata(metadata, follow_symlinks=follow_symlinks)
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def _copy_file(self, target):
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"""
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Copy the contents of this file to the given target.
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"""
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self._ensure_different_file(target)
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with self.open('rb') as source_f:
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try:
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with target.open('wb') as target_f:
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copyfileobj(source_f, target_f)
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except IsADirectoryError as e:
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if not target.exists():
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# Raise a less confusing exception.
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raise FileNotFoundError(
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f'Directory does not exist: {target}') from e
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else:
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raise
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def copy(self, target, *, follow_symlinks=True, dirs_exist_ok=False,
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preserve_metadata=False):
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"""
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Recursively copy this file or directory tree to the given destination.
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"""
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if not isinstance(target, PathBase):
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target = self.with_segments(target)
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self._ensure_distinct_path(target)
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stack = [(self, target)]
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while stack:
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src, dst = stack.pop()
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if not follow_symlinks and src.is_symlink():
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dst._symlink_to_target_of(src)
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if preserve_metadata:
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src._copy_metadata(dst, follow_symlinks=False)
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elif src.is_dir():
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children = src.iterdir()
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dst.mkdir(exist_ok=dirs_exist_ok)
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stack.extend((child, dst.joinpath(child.name))
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for child in children)
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if preserve_metadata:
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src._copy_metadata(dst)
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else:
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src._copy_file(dst)
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if preserve_metadata:
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src._copy_metadata(dst)
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return target
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copy = property(CopyWorker, doc=CopyWorker.__call__.__doc__)
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def copy_into(self, target_dir, *, follow_symlinks=True,
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dirs_exist_ok=False, preserve_metadata=False):
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