GH-128520: pathlib ABCs: reject empty pattern in ReadablePath.glob() (#127343)

For compatibility with `Path.glob()`, raise `ValueError` if an empty
pattern is given to `ReadablePath.glob()`.

Author: barneygale

Lib/pathlib/types.py

@@ -287,6 +287,8 @@ def glob(self, pattern, *, recurse_symlinks=True):
         anchor, parts = _explode_path(pattern)
         if anchor:
             raise NotImplementedError("Non-relative patterns are unsupported")
+        elif not parts:
+            raise ValueError(f"Unacceptable pattern: {pattern!r}")
         elif not recurse_symlinks:
             raise NotImplementedError("recurse_symlinks=False is unsupported")
         case_sensitive = self.parser.normcase('Aa') == 'Aa'

Lib/test/test_pathlib/test_read.py

@@ -127,6 +127,8 @@ def check(pattern, expected):
         check("**/file*",
               ["fileA", "dirA/linkC/fileB", "dirB/fileB", "dirC/fileC", "dirC/dirD/fileD",
                "linkB/fileB"])
+        with self.assertRaisesRegex(ValueError, 'Unacceptable pattern'):
+            list(p.glob(''))
 
     def test_walk_top_down(self):
         it = self.root.walk()