[Python-checkins] bpo-38811: Check for presence of os.link method in pathlib. (GH-17170)

[Serhiy Storchaka]

https://github.com/python/cpython/commit/111772fc27cfe388bc060f019d68a3e33481ec65
commit: 111772fc27cfe388bc060f019d68a3e33481ec65
branch: master
author: Toke Høiland-Jørgensen <toke at toke.dk>
committer: Serhiy Storchaka <storchaka at gmail.com>
date: 2019-11-17T19:06:38+02:00
summary:

bpo-38811: Check for presence of os.link method in pathlib. (GH-17170)

Fix also the Path.symplink() method implementation for the case when
symlinks are not supported.

files:
A Misc/NEWS.d/next/Library/2019-11-15-18-06-04.bpo-38811.AmdQ6M.rst
M Lib/pathlib.py
M Lib/test/test_pathlib.py

diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index d70fde0ea3b45..5142ff68d100d 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -418,7 +418,12 @@ def lchmod(self, pathobj, mode):
 
     unlink = os.unlink
 
-    link_to = os.link
+    if hasattr(os, "link"):
+        link_to = os.link
+    else:
+        @staticmethod
+        def link_to(self, target):
+            raise NotImplementedError("os.link() not available on this system")
 
     rmdir = os.rmdir
 
@@ -430,6 +435,7 @@ def lchmod(self, pathobj, mode):
         if supports_symlinks:
             symlink = os.symlink
         else:
+            @staticmethod
             def symlink(a, b, target_is_directory):
                 raise NotImplementedError("symlink() not available on this system")
     else:
diff --git a/Lib/test/test_pathlib.py b/Lib/test/test_pathlib.py
index 058a201aebc1d..d05b956be39f3 100644
--- a/Lib/test/test_pathlib.py
+++ b/Lib/test/test_pathlib.py
@@ -1759,6 +1759,7 @@ def test_rmdir(self):
         self.assertFileNotFound(p.stat)
         self.assertFileNotFound(p.unlink)
 
+    @unittest.skipUnless(hasattr(os, "link"), "os.link() is not present")
     def test_link_to(self):
         P = self.cls(BASE)
         p = P / 'fileA'
@@ -1778,6 +1779,15 @@ def test_link_to(self):
         self.assertEqual(os.stat(r).st_size, size)
         self.assertTrue(q.stat)
 
+    @unittest.skipIf(hasattr(os, "link"), "os.link() is present")
+    def test_link_to_not_implemented(self):
+        P = self.cls(BASE)
+        p = P / 'fileA'
+        # linking to another path.
+        q = P / 'dirA' / 'fileAA'
+        with self.assertRaises(NotImplementedError):
+            p.link_to(q)
+
     def test_rename(self):
         P = self.cls(BASE)
         p = P / 'fileA'
@@ -2011,6 +2021,15 @@ def test_symlink_to(self):
         self.assertTrue(link.is_dir())
         self.assertTrue(list(link.iterdir()))
 
+    @unittest.skipIf(support.can_symlink(), "symlink support is present")
+    def test_symlink_to_not_implemented(self):
+        P = self.cls(BASE)
+        target = P / 'fileA'
+        # Symlinking a path target.
+        link = P / 'dirA' / 'linkAA'
+        with self.assertRaises(NotImplementedError):
+            link.symlink_to(target)
+
     def test_is_dir(self):
         P = self.cls(BASE)
         self.assertTrue((P / 'dirA').is_dir())
diff --git a/Misc/NEWS.d/next/Library/2019-11-15-18-06-04.bpo-38811.AmdQ6M.rst b/Misc/NEWS.d/next/Library/2019-11-15-18-06-04.bpo-38811.AmdQ6M.rst
new file mode 100644
index 0000000000000..0e4a7f5bdf538
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-11-15-18-06-04.bpo-38811.AmdQ6M.rst
@@ -0,0 +1 @@
+Fix an unhandled exception in :mod:`pathlib` when :meth:`os.link` is missing. Patch by Toke Høiland-Jørgensen.