Move pathlib._abc.ParserBase to pathlib._types.Parser, and conver…

…t it to a runtime-checkable protocol.
python · barneygale · Dec 9, 2024 · Nov 30, 2024 · Nov 30, 2024 · Nov 30, 2024
commit 9febad0f5d7874ed76dee3c9660e02dd841aefd5
@@ -34,59 +34,6 @@ def _is_case_sensitive(parser):
     return parser.normcase('Aa') == 'Aa'
 
 
-
-class ParserBase:
-    """Base class for path parsers, which do low-level path manipulation.
-
-    Path parsers provide a subset of the os.path API, specifically those
-    functions needed to provide PurePathBase functionality. Each PurePathBase
-    subclass references its path parser via a 'parser' class attribute.
-
-    Every method in this base class raises an UnsupportedOperation exception.
-    """
-
-    @classmethod
-    def _unsupported_msg(cls, attribute):
-        return f"{cls.__name__}.{attribute} is unsupported"
-
-    @property
-    def sep(self):
-        """The character used to separate path components."""
-        raise UnsupportedOperation(self._unsupported_msg('sep'))
-
-    def join(self, path, *paths):
-        """Join path segments."""
-        raise UnsupportedOperation(self._unsupported_msg('join()'))
-
-    def split(self, path):
-        """Split the path into a pair (head, tail), where *head* is everything
-        before the final path separator, and *tail* is everything after.
-        Either part may be empty.
-        """
-        raise UnsupportedOperation(self._unsupported_msg('split()'))
-
-    def splitdrive(self, path):
-        """Split the path into a 2-item tuple (drive, tail), where *drive* is
-        a device name or mount point, and *tail* is everything after the
-        drive. Either part may be empty."""
-        raise UnsupportedOperation(self._unsupported_msg('splitdrive()'))
-
-    def splitext(self, path):
-        """Split the path into a pair (root, ext), where *ext* is empty or
-        begins with a period and contains at most one period,
-        and *root* is everything before the extension."""
-        raise UnsupportedOperation(self._unsupported_msg('splitext()'))
-
-    def normcase(self, path):
-        """Normalize the case of the path."""
-        raise UnsupportedOperation(self._unsupported_msg('normcase()'))
-
-    def isabs(self, path):
-        """Returns whether the path is absolute, i.e. unaffected by the
-        current directory or drive."""
-        raise UnsupportedOperation(self._unsupported_msg('isabs()'))
-
-
 class PathGlobber(_GlobberBase):
     """
     Class providing shell-style globbing for path objects.

@@ -0,0 +1,23 @@
+"""
+Protocols for supporting classes in pathlib.
+"""
+
+from typing import Protocol, runtime_checkable
+
+
+@runtime_checkable
+class Parser(Protocol):
+    """Protocol for path parsers, which do low-level path manipulation.
+
+    Path parsers provide a subset of the os.path API, specifically those
+    functions needed to provide PurePathBase functionality. Each PurePathBase
+    subclass references its path parser via a 'parser' class attribute.
+    """
+
+    sep: str
+    def join(self, path: str, *paths: str) -> str: ...
+    def split(self, path: str) -> (str, str): ...
+    def splitdrive(self, path: str) -> (str, str): ...
+    def splitext(self, path: str) -> (str, str): ...
+    def normcase(self, path: str) -> str: ...
+    def isabs(self, path: str) -> bool: ...
@@ -6,7 +6,7 @@
 import stat
 import unittest
 
-from pathlib._abc import UnsupportedOperation, ParserBase, PurePathBase, PathBase
+from pathlib._abc import UnsupportedOperation, PurePathBase, PathBase
 import posixpath
 
 from test.support import is_wasi
@@ -39,22 +39,6 @@ def test_is_notimplemented(self):
         self.assertTrue(issubclass(UnsupportedOperation, NotImplementedError))
         self.assertTrue(isinstance(UnsupportedOperation(), NotImplementedError))
 
-
-class ParserBaseTest(unittest.TestCase):
-    cls = ParserBase
-
-    def test_unsupported_operation(self):
-        m = self.cls()
-        e = UnsupportedOperation
-        with self.assertRaises(e):
-            m.sep
-        self.assertRaises(e, m.join, 'foo')
-        self.assertRaises(e, m.split, 'foo')
-        self.assertRaises(e, m.splitdrive, 'foo')
-        self.assertRaises(e, m.splitext, 'foo')
-        self.assertRaises(e, m.normcase, 'foo')
-        self.assertRaises(e, m.isabs, 'foo')
-
 #
 # Tests for the pure classes.
 #

diff --git a/Lib/test/test_pathlib/test_pathlib_types.py b/Lib/test/test_pathlib/test_pathlib_types.py
@@ -0,0 +1,15 @@
+import ntpath
+import posixpath
+import unittest
+
+from pathlib._types import Parser
+
+
+class ParserTest(unittest.TestCase):
+    def test_path_modules(self):
+        self.assertTrue(isinstance(posixpath, Parser))
+        self.assertTrue(isinstance(ntpath, Parser))
+
+
+if __name__ == "__main__":
+    unittest.main()