GH-130614: pathlib ABCs: revise test suite for readable paths (#131018)

Test `pathlib.types._ReadablePath` in a dedicated test module. These tests
cover `ReadableZipPath`, `ReadableLocalPath` and `Path`, where the former
two classes are implementations of `_ReadablePath` for use in tests.

Lib/test/test_pathlib/support/local_path.py

@@ -0,0 +1,145 @@
+"""
+Implementation of ReadablePath for local paths, for use in pathlib tests.
+
+LocalPathGround is also defined here. It helps establish the "ground truth"
+about local paths in tests.
+"""
+
+import os
+import pathlib.types
+
+from test.support import os_helper
+from test.test_pathlib.support.lexical_path import LexicalPath
+
+
+class LocalPathGround:
+    can_symlink = os_helper.can_symlink()
+
+    def __init__(self, path_cls):
+        self.path_cls = path_cls
+
+    def setup(self, local_suffix=""):
+        root = self.path_cls(os_helper.TESTFN + local_suffix)
+        os.mkdir(root)
+        return root
+
+    def teardown(self, root):
+        os_helper.rmtree(root)
+
+    def create_file(self, p, data=b''):
+        with open(p, 'wb') as f:
+            f.write(data)
+
+    def create_dir(self, p):
+        os.mkdir(p)
+
+    def create_symlink(self, p, target):
+        os.symlink(target, p)
+
+    def create_hierarchy(self, p):
+        os.mkdir(os.path.join(p, 'dirA'))
+        os.mkdir(os.path.join(p, 'dirB'))
+        os.mkdir(os.path.join(p, 'dirC'))
+        os.mkdir(os.path.join(p, 'dirC', 'dirD'))
+        with open(os.path.join(p, 'fileA'), 'wb') as f:
+            f.write(b"this is file A\n")
+        with open(os.path.join(p, 'dirB', 'fileB'), 'wb') as f:
+            f.write(b"this is file B\n")
+        with open(os.path.join(p, 'dirC', 'fileC'), 'wb') as f:
+            f.write(b"this is file C\n")
+        with open(os.path.join(p, 'dirC', 'novel.txt'), 'wb') as f:
+            f.write(b"this is a novel\n")
+        with open(os.path.join(p, 'dirC', 'dirD', 'fileD'), 'wb') as f:
+            f.write(b"this is file D\n")
+        if self.can_symlink:
+            # Relative symlinks.
+            os.symlink('fileA', os.path.join(p, 'linkA'))
+            os.symlink('non-existing', os.path.join(p, 'brokenLink'))
+            os.symlink('dirB',
+                       os.path.join(p, 'linkB'),
+                       target_is_directory=True)
+            os.symlink(os.path.join('..', 'dirB'),
+                       os.path.join(p, 'dirA', 'linkC'),
+                       target_is_directory=True)
+            # Broken symlink (pointing to itself).
+            os.symlink('brokenLinkLoop', os.path.join(p, 'brokenLinkLoop'))
+
+    isdir = staticmethod(os.path.isdir)
+    isfile = staticmethod(os.path.isfile)
+    islink = staticmethod(os.path.islink)
+    readlink = staticmethod(os.readlink)
+
+    def readtext(self, p):
+        with open(p, 'r') as f:
+            return f.read()
+
+    def readbytes(self, p):
+        with open(p, 'rb') as f:
+            return f.read()
+
+
+class LocalPathInfo(pathlib.types.PathInfo):
+    """
+    Simple implementation of PathInfo for a local path
+    """
+    __slots__ = ('_path', '_exists', '_is_dir', '_is_file', '_is_symlink')
+
+    def __init__(self, path):
+        self._path = str(path)
+        self._exists = None
+        self._is_dir = None
+        self._is_file = None
+        self._is_symlink = None
+
+    def exists(self, *, follow_symlinks=True):
+        """Whether this path exists."""
+        if not follow_symlinks and self.is_symlink():
+            return True
+        if self._exists is None:
+            self._exists = os.path.exists(self._path)
+        return self._exists
+
+    def is_dir(self, *, follow_symlinks=True):
+        """Whether this path is a directory."""
+        if not follow_symlinks and self.is_symlink():
+            return False
+        if self._is_dir is None:
+            self._is_dir = os.path.isdir(self._path)
+        return self._is_dir
+
+    def is_file(self, *, follow_symlinks=True):
+        """Whether this path is a regular file."""
+        if not follow_symlinks and self.is_symlink():
+            return False
+        if self._is_file is None:
+            self._is_file = os.path.isfile(self._path)
+        return self._is_file
+
+    def is_symlink(self):
+        """Whether this path is a symbolic link."""
+        if self._is_symlink is None:
+            self._is_symlink = os.path.islink(self._path)
+        return self._is_symlink
+
+
+class ReadableLocalPath(pathlib.types._ReadablePath, LexicalPath):
+    """
+    Simple implementation of a ReadablePath class for local filesystem paths.
+    """
+    __slots__ = ('info',)
+
+    def __init__(self, *pathsegments):
+        super().__init__(*pathsegments)
+        self.info = LocalPathInfo(self)
+
+    def __fspath__(self):
+        return str(self)
+
+    def __open_rb__(self, buffering=-1):
+        return open(self, 'rb')
+
+    def iterdir(self):
+        return (self / name for name in os.listdir(self))
+
+    def readlink(self):
+        return self.with_segments(os.readlink(self))