GH-127381: pathlib ABCs: remove PathBase.samefile() and rarer is_*() (#127709)

Remove `PathBase.samefile()`, which is fairly specific to the local FS, and
relies on `stat()`, which we're aiming to remove from `PathBase`.

Also remove `PathBase.is_mount()`, `is_junction()`, `is_block_device()`,
`is_char_device()`, `is_fifo()` and `is_socket()`. These rely on POSIX
file type numbers that we're aiming to remove from the `PathBase` API.

Author: barneygale

Lib/pathlib/_abc.py

@@ -16,7 +16,7 @@
 import posixpath
 from errno import EINVAL
 from glob import _GlobberBase, _no_recurse_symlinks
-from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
+from stat import S_ISDIR, S_ISLNK, S_ISREG
 from pathlib._os import copyfileobj
 
 
@@ -408,26 +408,6 @@ def is_file(self, *, follow_symlinks=True):
         except (OSError, ValueError):
             return False
 
-    def is_mount(self):
-        """
-        Check if this path is a mount point
-        """
-        # Need to exist and be a dir
-        if not self.exists() or not self.is_dir():
-            return False
-
-        try:
-            parent_dev = self.parent.stat().st_dev
-        except OSError:
-            return False
-
-        dev = self.stat().st_dev
-        if dev != parent_dev:
-            return True
-        ino = self.stat().st_ino
-        parent_ino = self.parent.stat().st_ino
-        return ino == parent_ino
-
     def is_symlink(self):
         """
         Whether this path is a symbolic link.
@@ -437,76 +417,11 @@ def is_symlink(self):
         except (OSError, ValueError):
             return False
 
-    def is_junction(self):
-        """
-        Whether this path is a junction.
-        """
-        # Junctions are a Windows-only feature, not present in POSIX nor the
-        # majority of virtual filesystems. There is no cross-platform idiom
-        # to check for junctions (using stat().st_mode).
-        return False
-
-    def is_block_device(self):
-        """
-        Whether this path is a block device.
-        """
-        try:
-            return S_ISBLK(self.stat().st_mode)
-        except (OSError, ValueError):
-            return False
-
-    def is_char_device(self):
-        """
-        Whether this path is a character device.
-        """
-        try:
-            return S_ISCHR(self.stat().st_mode)
-        except (OSError, ValueError):
-            return False
-
-    def is_fifo(self):
-        """
-        Whether this path is a FIFO.
-        """
-        try:
-            return S_ISFIFO(self.stat().st_mode)
-        except (OSError, ValueError):
-            return False
-
-    def is_socket(self):
-        """
-        Whether this path is a socket.
-        """
-        try:
-            return S_ISSOCK(self.stat().st_mode)
-        except (OSError, ValueError):
-            return False
-
-    def samefile(self, other_path):
-        """Return whether other_path is the same or not as this file
-        (as returned by os.path.samefile()).
-        """
-        st = self.stat()
-        try:
-            other_st = other_path.stat()
-        except AttributeError:
-            other_st = self.with_segments(other_path).stat()
-        return (st.st_ino == other_st.st_ino and
-                st.st_dev == other_st.st_dev)
-
     def _ensure_different_file(self, other_path):
         """
         Raise OSError(EINVAL) if both paths refer to the same file.
         """
-        try:
-            if not self.samefile(other_path):
-                return
-        except (OSError, ValueError):
-            return
-        err = OSError(EINVAL, "Source and target are the same file")
-        err.filename = str(self)
-        err.filename2 = str(other_path)
-        raise err
+        pass
 
     def _ensure_distinct_path(self, other_path):
         """

Lib/pathlib/_local.py

@@ -4,9 +4,10 @@
 import os
 import posixpath
 import sys
-from errno import EXDEV
+from errno import EINVAL, EXDEV
 from glob import _StringGlobber
 from itertools import chain
+from stat import S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
 from _collections_abc import Sequence
 
 try:
@@ -596,6 +597,68 @@ def is_junction(self):
         """
         return os.path.isjunction(self)
 
+    def is_block_device(self):
+        """
+        Whether this path is a block device.
+        """
+        try:
+            return S_ISBLK(self.stat().st_mode)
+        except (OSError, ValueError):
+            return False
+
+    def is_char_device(self):
+        """
+        Whether this path is a character device.
+        """
+        try:
+            return S_ISCHR(self.stat().st_mode)
+        except (OSError, ValueError):
+            return False
+
+    def is_fifo(self):
+        """
+        Whether this path is a FIFO.
+        """
+        try:
+            return S_ISFIFO(self.stat().st_mode)
+        except (OSError, ValueError):
+            return False
+
+    def is_socket(self):
+        """
+        Whether this path is a socket.
+        """
+        try:
+            return S_ISSOCK(self.stat().st_mode)
+        except (OSError, ValueError):
+            return False
+
+    def samefile(self, other_path):
+        """Return whether other_path is the same or not as this file
+        (as returned by os.path.samefile()).
+        """
+        st = self.stat()
+        try:
+            other_st = other_path.stat()
+        except AttributeError:
+            other_st = self.with_segments(other_path).stat()
+        return (st.st_ino == other_st.st_ino and
+                st.st_dev == other_st.st_dev)
+
+    def _ensure_different_file(self, other_path):
+        """
+        Raise OSError(EINVAL) if both paths refer to the same file.
+        """
+        try:
+            if not self.samefile(other_path):
+                return
+        except (OSError, ValueError):
+            return
+        err = OSError(EINVAL, "Source and target are the same file")
+        err.filename = str(self)
+        err.filename2 = str(other_path)
+        raise err
+
     def open(self, mode='r', buffering=-1, encoding=None,
              errors=None, newline=None):
         """

Lib/test/test_pathlib/test_pathlib.py

@@ -1786,13 +1786,31 @@ def test_lstat_nosymlink(self):
         st = p.stat()
         self.assertEqual(st, p.lstat())
 
-    def test_is_junction(self):
+    def test_is_junction_false(self):
+        P = self.cls(self.base)
+        self.assertFalse((P / 'fileA').is_junction())
+        self.assertFalse((P / 'dirA').is_junction())
+        self.assertFalse((P / 'non-existing').is_junction())
+        self.assertFalse((P / 'fileA' / 'bah').is_junction())
+        self.assertFalse((P / 'fileA\udfff').is_junction())
+        self.assertFalse((P / 'fileA\x00').is_junction())
+
+    def test_is_junction_true(self):
         P = self.cls(self.base)
 
         with mock.patch.object(P.parser, 'isjunction'):
             self.assertEqual(P.is_junction(), P.parser.isjunction.return_value)
             P.parser.isjunction.assert_called_once_with(P)
 
+    def test_is_fifo_false(self):
+        P = self.cls(self.base)
+        self.assertFalse((P / 'fileA').is_fifo())
+        self.assertFalse((P / 'dirA').is_fifo())
+        self.assertFalse((P / 'non-existing').is_fifo())
+        self.assertFalse((P / 'fileA' / 'bah').is_fifo())
+        self.assertIs((P / 'fileA\udfff').is_fifo(), False)
+        self.assertIs((P / 'fileA\x00').is_fifo(), False)
+
     @unittest.skipUnless(hasattr(os, "mkfifo"), "os.mkfifo() required")
     @unittest.skipIf(sys.platform == "vxworks",
                     "fifo requires special path on VxWorks")
@@ -1808,6 +1826,15 @@ def test_is_fifo_true(self):
         self.assertIs(self.cls(self.base, 'myfifo\udfff').is_fifo(), False)
         self.assertIs(self.cls(self.base, 'myfifo\x00').is_fifo(), False)
 
+    def test_is_socket_false(self):
+        P = self.cls(self.base)
+        self.assertFalse((P / 'fileA').is_socket())
+        self.assertFalse((P / 'dirA').is_socket())
+        self.assertFalse((P / 'non-existing').is_socket())
+        self.assertFalse((P / 'fileA' / 'bah').is_socket())
+        self.assertIs((P / 'fileA\udfff').is_socket(), False)
+        self.assertIs((P / 'fileA\x00').is_socket(), False)
+
     @unittest.skipUnless(hasattr(socket, "AF_UNIX"), "Unix sockets required")
     @unittest.skipIf(
         is_emscripten, "Unix sockets are not implemented on Emscripten."
@@ -1831,6 +1858,24 @@ def test_is_socket_true(self):
         self.assertIs(self.cls(self.base, 'mysock\udfff').is_socket(), False)
         self.assertIs(self.cls(self.base, 'mysock\x00').is_socket(), False)
 
+    def test_is_block_device_false(self):
+        P = self.cls(self.base)
+        self.assertFalse((P / 'fileA').is_block_device())
+        self.assertFalse((P / 'dirA').is_block_device())
+        self.assertFalse((P / 'non-existing').is_block_device())
+        self.assertFalse((P / 'fileA' / 'bah').is_block_device())
+        self.assertIs((P / 'fileA\udfff').is_block_device(), False)
+        self.assertIs((P / 'fileA\x00').is_block_device(), False)
+
+    def test_is_char_device_false(self):
+        P = self.cls(self.base)
+        self.assertFalse((P / 'fileA').is_char_device())
+        self.assertFalse((P / 'dirA').is_char_device())
+        self.assertFalse((P / 'non-existing').is_char_device())
+        self.assertFalse((P / 'fileA' / 'bah').is_char_device())
+        self.assertIs((P / 'fileA\udfff').is_char_device(), False)
+        self.assertIs((P / 'fileA\x00').is_char_device(), False)
+
     def test_is_char_device_true(self):
         # os.devnull should generally be a char device.
         P = self.cls(os.devnull)
@@ -1842,14 +1887,42 @@ def test_is_char_device_true(self):
         self.assertIs(self.cls(f'{os.devnull}\udfff').is_char_device(), False)
         self.assertIs(self.cls(f'{os.devnull}\x00').is_char_device(), False)
 
-    def test_is_mount_root(self):
+    def test_is_mount(self):
+        P = self.cls(self.base)
+        self.assertFalse((P / 'fileA').is_mount())
+        self.assertFalse((P / 'dirA').is_mount())
+        self.assertFalse((P / 'non-existing').is_mount())
+        self.assertFalse((P / 'fileA' / 'bah').is_mount())
+        if self.can_symlink:
+            self.assertFalse((P / 'linkA').is_mount())
         if os.name == 'nt':
             R = self.cls('c:\\')
         else:
             R = self.cls('/')
         self.assertTrue(R.is_mount())
         self.assertFalse((R / '\udfff').is_mount())
 
+    def test_samefile(self):
+        parser = self.parser
+        fileA_path = parser.join(self.base, 'fileA')
+        fileB_path = parser.join(self.base, 'dirB', 'fileB')
+        p = self.cls(fileA_path)
+        pp = self.cls(fileA_path)
+        q = self.cls(fileB_path)
+        self.assertTrue(p.samefile(fileA_path))
+        self.assertTrue(p.samefile(pp))
+        self.assertFalse(p.samefile(fileB_path))
+        self.assertFalse(p.samefile(q))
+        # Test the non-existent file case
+        non_existent = parser.join(self.base, 'foo')
+        r = self.cls(non_existent)
+        self.assertRaises(FileNotFoundError, p.samefile, r)
+        self.assertRaises(FileNotFoundError, p.samefile, non_existent)
+        self.assertRaises(FileNotFoundError, r.samefile, p)
+        self.assertRaises(FileNotFoundError, r.samefile, non_existent)
+        self.assertRaises(FileNotFoundError, r.samefile, r)
+        self.assertRaises(FileNotFoundError, r.samefile, non_existent)
+
     def test_passing_kwargs_errors(self):
         with self.assertRaises(TypeError):
             self.cls(foo="bar")