pythonGH-139174: Prepare pathlib.Path.info for new methods

Merge `_PathInfoBase`, `_WindowsPathInfo`, `_PosixPathInfo` and
`DirEntryInfo` classes into a single `LocalPathInfo` class. Abandon use of
`os.path.exists()` etc on Windows, and switch to using `stat()` like the
Posix implementation; this might be a little bit slower but there's value
in making the code more easily maintainable by someone other than myself!

Author: barneygale

Lib/pathlib/__init__.py

@@ -27,7 +27,7 @@
     grp = None
 
 from pathlib._os import (
-    PathInfo, DirEntryInfo,
+    LocalPathInfo,
     vfsopen, vfspath,
     ensure_different_files, ensure_distinct_paths,
     copyfile2, copyfileobj, copy_info,
@@ -637,7 +637,7 @@ def info(self):
         try:
             return self._info
         except AttributeError:
-            self._info = PathInfo(self)
+            self._info = LocalPathInfo(str(self))
             return self._info
 
     def stat(self, *, follow_symlinks=True):
@@ -817,7 +817,7 @@ def _filter_trailing_slash(self, paths):
     def _from_dir_entry(self, dir_entry, path_str):
         path = self.with_segments(path_str)
         path._str = path_str
-        path._info = DirEntryInfo(dir_entry)
+        path._info = LocalPathInfo(path_str, dir_entry)
         return path
 
     def iterdir(self):

Lib/pathlib/_os.py

@@ -363,47 +363,46 @@ def copy_info(info, target, follow_symlinks=True):
                 raise
 
 
-class _PathInfoBase:
-    __slots__ = ('_path', '_stat_result', '_lstat_result')
+_STAT_RESULT_ERROR = []  # falsy sentinel indicating stat() failed.
 
-    def __init__(self, path):
-        self._path = str(path)
+
+class LocalPathInfo:
+    """Implementation of pathlib.types.PathInfo that provides information
+    about local filesystem paths. Don't try to construct it yourself."""
+    __slots__ = ('_path', '_dir_entry', '_stat_result', '_lstat_result')
+
+    def __init__(self, path, dir_entry=None):
+        self._path = path
+        self._dir_entry = dir_entry
+        self._stat_result = None
+        self._lstat_result = None
 
     def __repr__(self):
         path_type = "WindowsPath" if os.name == "nt" else "PosixPath"
         return f"<{path_type}.info>"
 
-    def _stat(self, *, follow_symlinks=True, ignore_errors=False):
-        """Return the status as an os.stat_result, or None if stat() fails and
-        ignore_errors is true."""
+    def _stat(self, *, follow_symlinks=True):
+        """Return the status as an os.stat_result."""
         if follow_symlinks:
-            try:
-                result = self._stat_result
-            except AttributeError:
-                pass
-            else:
-                if ignore_errors or result is not None:
-                    return result
-            try:
-                self._stat_result = os.stat(self._path)
-            except (OSError, ValueError):
-                self._stat_result = None
-                if not ignore_errors:
+            if not self._stat_result:
+                try:
+                    if self._dir_entry:
+                        self._stat_result = self._dir_entry.stat()
+                    else:
+                        self._stat_result = os.stat(self._path)
+                except (OSError, ValueError):
+                    self._stat_result = _STAT_RESULT_ERROR
                     raise
             return self._stat_result
         else:
-            try:
-                result = self._lstat_result
-            except AttributeError:
-                pass
-            else:
-                if ignore_errors or result is not None:
-                    return result
-            try:
-                self._lstat_result = os.lstat(self._path)
-            except (OSError, ValueError):
-                self._lstat_result = None
-                if not ignore_errors:
+            if not self._lstat_result:
+                try:
+                    if self._dir_entry:
+                        self._stat_result = self._dir_entry.stat(follow_symlinks=False)
+                    else:
+                        self._lstat_result = os.lstat(self._path)
+                except (OSError, ValueError):
+                    self._lstat_result = _STAT_RESULT_ERROR
                     raise
             return self._lstat_result
 
@@ -442,141 +441,75 @@ def _xattrs(self, *, follow_symlinks=True):
                     raise
                 return []
 
-
-class _WindowsPathInfo(_PathInfoBase):
-    """Implementation of pathlib.types.PathInfo that provides status
-    information for Windows paths. Don't try to construct it yourself."""
-    __slots__ = ('_exists', '_is_dir', '_is_file', '_is_symlink')
-
     def exists(self, *, follow_symlinks=True):
         """Whether this path exists."""
-        if not follow_symlinks and self.is_symlink():
-            return True
-        try:
-            return self._exists
-        except AttributeError:
-            if os.path.exists(self._path):
-                self._exists = True
-                return True
-            else:
-                self._exists = self._is_dir = self._is_file = False
+        if follow_symlinks:
+            if self._stat_result is _STAT_RESULT_ERROR:
                 return False
-
-    def is_dir(self, *, follow_symlinks=True):
-        """Whether this path is a directory."""
-        if not follow_symlinks and self.is_symlink():
-            return False
-        try:
-            return self._is_dir
-        except AttributeError:
-            if os.path.isdir(self._path):
-                self._is_dir = self._exists = True
-                return True
-            else:
-                self._is_dir = False
+        else:
+            if self._lstat_result is _STAT_RESULT_ERROR:
                 return False
-
-    def is_file(self, *, follow_symlinks=True):
-        """Whether this path is a regular file."""
-        if not follow_symlinks and self.is_symlink():
-            return False
-        try:
-            return self._is_file
-        except AttributeError:
-            if os.path.isfile(self._path):
-                self._is_file = self._exists = True
+            elif self._dir_entry:
                 return True
-            else:
-                self._is_file = False
-                return False
-
-    def is_symlink(self):
-        """Whether this path is a symbolic link."""
         try:
-            return self._is_symlink
-        except AttributeError:
-            self._is_symlink = os.path.islink(self._path)
-            return self._is_symlink
-
-
-class _PosixPathInfo(_PathInfoBase):
-    """Implementation of pathlib.types.PathInfo that provides status
-    information for POSIX paths. Don't try to construct it yourself."""
-    __slots__ = ()
-
-    def exists(self, *, follow_symlinks=True):
-        """Whether this path exists."""
-        st = self._stat(follow_symlinks=follow_symlinks, ignore_errors=True)
-        if st is None:
-            return False
-        return True
-
-    def is_dir(self, *, follow_symlinks=True):
-        """Whether this path is a directory."""
-        st = self._stat(follow_symlinks=follow_symlinks, ignore_errors=True)
-        if st is None:
-            return False
-        return S_ISDIR(st.st_mode)
-
-    def is_file(self, *, follow_symlinks=True):
-        """Whether this path is a regular file."""
-        st = self._stat(follow_symlinks=follow_symlinks, ignore_errors=True)
-        if st is None:
-            return False
-        return S_ISREG(st.st_mode)
-
-    def is_symlink(self):
-        """Whether this path is a symbolic link."""
-        st = self._stat(follow_symlinks=False, ignore_errors=True)
-        if st is None:
+            self._stat(follow_symlinks=follow_symlinks)
+        except (OSError, ValueError):
             return False
-        return S_ISLNK(st.st_mode)
-
-
-PathInfo = _WindowsPathInfo if os.name == 'nt' else _PosixPathInfo
-
-
-class DirEntryInfo(_PathInfoBase):
-    """Implementation of pathlib.types.PathInfo that provides status
-    information by querying a wrapped os.DirEntry object. Don't try to
-    construct it yourself."""
-    __slots__ = ('_entry',)
-
-    def __init__(self, entry):
-        super().__init__(entry.path)
-        self._entry = entry
-
-    def _stat(self, *, follow_symlinks=True, ignore_errors=False):
-        try:
-            return self._entry.stat(follow_symlinks=follow_symlinks)
-        except OSError:
-            if not ignore_errors:
-                raise
-            return None
-
-    def exists(self, *, follow_symlinks=True):
-        """Whether this path exists."""
-        if not follow_symlinks:
+        else:
             return True
-        return self._stat(ignore_errors=True) is not None
 
     def is_dir(self, *, follow_symlinks=True):
         """Whether this path is a directory."""
+        if self._dir_entry:
+            try:
+                return self._dir_entry.is_dir(follow_symlinks=follow_symlinks)
+            except OSError:
+                return False
+        elif follow_symlinks:
+            if self._stat_result is _STAT_RESULT_ERROR:
+                return False
+        else:
+            if self._lstat_result is _STAT_RESULT_ERROR:
+                return False
         try:
-            return self._entry.is_dir(follow_symlinks=follow_symlinks)
-        except OSError:
+            st = self._stat(follow_symlinks=follow_symlinks)
+        except (OSError, ValueError):
             return False
+        else:
+            return S_ISDIR(st.st_mode)
 
     def is_file(self, *, follow_symlinks=True):
         """Whether this path is a regular file."""
+        if self._dir_entry:
+            try:
+                return self._dir_entry.is_file(follow_symlinks=follow_symlinks)
+            except OSError:
+                return False
+        elif follow_symlinks:
+            if self._stat_result is _STAT_RESULT_ERROR:
+                return False
+        else:
+            if self._lstat_result is _STAT_RESULT_ERROR:
+                return False
         try:
-            return self._entry.is_file(follow_symlinks=follow_symlinks)
-        except OSError:
+            st = self._stat(follow_symlinks=follow_symlinks)
+        except (OSError, ValueError):
             return False
+        else:
+            return S_ISREG(st.st_mode)
 
     def is_symlink(self):
         """Whether this path is a symbolic link."""
+        if self._dir_entry:
+            try:
+                return self._dir_entry.is_symlink()
+            except OSError:
+                return False
+        elif self._lstat_result is _STAT_RESULT_ERROR:
+            return False
         try:
-            return self._entry.is_symlink()
-        except OSError:
+            st = self._stat(follow_symlinks=False)
+        except (OSError, ValueError):
             return False
+        else:
+            return S_ISLNK(st.st_mode)