bpo-43757: Make pathlib use os.path.realpath() to resolve symlinks in a path (GH-25264)

Also adds a new "strict" argument to realpath() to avoid changing the default behaviour of pathlib while sharing the implementation.

1 files changed, 58 insertions, 2 deletions

diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index f97aca5..661c59d 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -271,6 +271,17 @@ class TestNtpath(NtpathTestCase):
 
     @os_helper.skip_unless_symlink
     @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
+    def test_realpath_strict(self):
+        # Bug #43757: raise FileNotFoundError in strict mode if we encounter
+        # a path that does not exist.
+        ABSTFN = ntpath.abspath(os_helper.TESTFN)
+        os.symlink(ABSTFN + "1", ABSTFN)
+        self.addCleanup(os_helper.unlink, ABSTFN)
+        self.assertRaises(FileNotFoundError, ntpath.realpath, ABSTFN, strict=True)
+        self.assertRaises(FileNotFoundError, ntpath.realpath, ABSTFN + "2", strict=True)
+
+    @os_helper.skip_unless_symlink
+    @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
     def test_realpath_relative(self):
         ABSTFN = ntpath.abspath(os_helper.TESTFN)
         open(ABSTFN, "wb").close()
@@ -340,8 +351,9 @@ class TestNtpath(NtpathTestCase):
     @os_helper.skip_unless_symlink
     @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
     def test_realpath_symlink_loops(self):
-        # Symlink loops are non-deterministic as to which path is returned, but
-        # it will always be the fully resolved path of one member of the cycle
+        # Symlink loops in non-strict mode are non-deterministic as to which
+        # path is returned, but it will always be the fully resolved path of
+        # one member of the cycle
         ABSTFN = ntpath.abspath(os_helper.TESTFN)
         self.addCleanup(os_helper.unlink, ABSTFN)
         self.addCleanup(os_helper.unlink, ABSTFN + "1")
@@ -385,6 +397,50 @@ class TestNtpath(NtpathTestCase):
 
     @os_helper.skip_unless_symlink
     @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
+    def test_realpath_symlink_loops_strict(self):
+        # Symlink loops raise OSError in strict mode
+        ABSTFN = ntpath.abspath(os_helper.TESTFN)
+        self.addCleanup(os_helper.unlink, ABSTFN)
+        self.addCleanup(os_helper.unlink, ABSTFN + "1")
+        self.addCleanup(os_helper.unlink, ABSTFN + "2")
+        self.addCleanup(os_helper.unlink, ABSTFN + "y")
+        self.addCleanup(os_helper.unlink, ABSTFN + "c")
+        self.addCleanup(os_helper.unlink, ABSTFN + "a")
+
+        os.symlink(ABSTFN, ABSTFN)
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN, strict=True)
+
+        os.symlink(ABSTFN + "1", ABSTFN + "2")
+        os.symlink(ABSTFN + "2", ABSTFN + "1")
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1", strict=True)
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "2", strict=True)
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1\\x", strict=True)
+        # Windows eliminates '..' components before resolving links, so the
+        # following call is not expected to raise.
+        self.assertPathEqual(ntpath.realpath(ABSTFN + "1\\..", strict=True),
+                             ntpath.dirname(ABSTFN))
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1\\..\\x", strict=True)
+        os.symlink(ABSTFN + "x", ABSTFN + "y")
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1\\..\\"
+                                             + ntpath.basename(ABSTFN) + "y",
+                                             strict=True)
+        self.assertRaises(OSError, ntpath.realpath,
+                          ABSTFN + "1\\..\\" + ntpath.basename(ABSTFN) + "1",
+                          strict=True)
+
+        os.symlink(ntpath.basename(ABSTFN) + "a\\b", ABSTFN + "a")
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "a", strict=True)
+
+        os.symlink("..\\" + ntpath.basename(ntpath.dirname(ABSTFN))
+                   + "\\" + ntpath.basename(ABSTFN) + "c", ABSTFN + "c")
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "c", strict=True)
+
+        # Test using relative path as well.
+        self.assertRaises(OSError, ntpath.realpath, ntpath.basename(ABSTFN),
+                          strict=True)
+
+    @os_helper.skip_unless_symlink
+    @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
     def test_realpath_symlink_prefix(self):
         ABSTFN = ntpath.abspath(os_helper.TESTFN)
         self.addCleanup(os_helper.unlink, ABSTFN + "3")