GH-125413: Add private metadata methods to pathlib.Path.info

Add the following private methods to `pathlib.Path.info`:

- `_get_mode()`: returns the POSIX file mode (`st_mode`), or zero if
  `os.stat()` fails.
- `_get_times_ns()`: returns the access and modify times in nanoseconds
  (`st_atime_ns` and `st_mtime_ns`), or zeroes if `os.stat()` fails.
- `_get_flags()`: returns the BSD file flags (`st_flags`), or zero if
  `os.stat()` fails.
- `_get_xattrs()`: returns the file extended attributes as a list of
  key, value pairs, or an empty list if `listxattr()` or `getattr()` fail.

These methods replace `LocalCopyReader.read_metadata()`, and so we can
delete the `CopyReader` and `LocalCopyReader` classes. Rather than reading
metadata via `source._copy_reader.read_metadata()`, we instead call
`source.info._get_mode()`, `_get_times_ns()`, etc.

Copying metadata is only supported for local-to-local copies at the moment.
To support copying between arbitrary `ReadablePath` and `WritablePath`
objects, we'd need to make the new methods public and documented.

Author: barneygale

Lib/pathlib/_abc.py

@@ -14,7 +14,7 @@
 import functools
 import posixpath
 from glob import _PathGlobber, _no_recurse_symlinks
-from pathlib._os import magic_open, CopyReader, CopyWriter
+from pathlib._os import magic_open, CopyWriter
 
 
 @functools.cache
@@ -354,8 +354,6 @@ def readlink(self):
         """
         raise NotImplementedError
 
-    _copy_reader = property(CopyReader)
-
     def copy(self, target, follow_symlinks=True, dirs_exist_ok=False,
              preserve_metadata=False):
         """

Lib/pathlib/_local.py

@@ -19,7 +19,7 @@
 except ImportError:
     grp = None
 
-from pathlib._os import LocalCopyReader, LocalCopyWriter, PathInfo, DirEntryInfo
+from pathlib._os import LocalCopyWriter, PathInfo, DirEntryInfo
 from pathlib._abc import JoinablePath, ReadablePath, WritablePath
 
 
@@ -1055,7 +1055,6 @@ def replace(self, target):
         os.replace(self, target)
         return self.with_segments(target)
 
-    _copy_reader = property(LocalCopyReader)
     _copy_writer = property(LocalCopyWriter)
 
     def move(self, target):