bpo-34384: Fix os.readlink() on Windows (GH-8740)

os.readlink() now accepts path-like and bytes objects on Windows.
Previously, support for path-like and bytes objects was only
implemented on Unix.

This commit also merges Unix and Windows implementations of
os.readlink() in one function and adds basic unit tests to increase
test coverage of the function.

1 files changed, 47 insertions, 0 deletions

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index a140ae0..6658a61 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -2039,6 +2039,53 @@ class Win32ListdirTests(unittest.TestCase):
                 [os.fsencode(path) for path in self.created_paths])
 
 
+@unittest.skipUnless(hasattr(os, 'readlink'), 'needs os.readlink()')
+class ReadlinkTests(unittest.TestCase):
+    filelink = 'readlinktest'
+    filelink_target = os.path.abspath(__file__)
+    filelinkb = os.fsencode(filelink)
+    filelinkb_target = os.fsencode(filelink_target)
+
+    def setUp(self):
+        self.assertTrue(os.path.exists(self.filelink_target))
+        self.assertTrue(os.path.exists(self.filelinkb_target))
+        self.assertFalse(os.path.exists(self.filelink))
+        self.assertFalse(os.path.exists(self.filelinkb))
+
+    def test_not_symlink(self):
+        filelink_target = FakePath(self.filelink_target)
+        self.assertRaises(OSError, os.readlink, self.filelink_target)
+        self.assertRaises(OSError, os.readlink, filelink_target)
+
+    def test_missing_link(self):
+        self.assertRaises(FileNotFoundError, os.readlink, 'missing-link')
+        self.assertRaises(FileNotFoundError, os.readlink,
+                          FakePath('missing-link'))
+
+    @support.skip_unless_symlink
+    def test_pathlike(self):
+        os.symlink(self.filelink_target, self.filelink)
+        self.addCleanup(support.unlink, self.filelink)
+        filelink = FakePath(self.filelink)
+        self.assertEqual(os.readlink(filelink), self.filelink_target)
+
+    @support.skip_unless_symlink
+    def test_pathlike_bytes(self):
+        os.symlink(self.filelinkb_target, self.filelinkb)
+        self.addCleanup(support.unlink, self.filelinkb)
+        path = os.readlink(FakePath(self.filelinkb))
+        self.assertEqual(path, self.filelinkb_target)
+        self.assertIsInstance(path, bytes)
+
+    @support.skip_unless_symlink
+    def test_bytes(self):
+        os.symlink(self.filelinkb_target, self.filelinkb)
+        self.addCleanup(support.unlink, self.filelinkb)
+        path = os.readlink(self.filelinkb)
+        self.assertEqual(path, self.filelinkb_target)
+        self.assertIsInstance(path, bytes)
+
+
 @unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
 @support.skip_unless_symlink
 class Win32SymlinkTests(unittest.TestCase):