From 0a08d7a09537b2ccfc93c5a81bd36cf5f1b1e92d Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <solipsis@pitrou.net>
Date: Fri, 6 Jan 2012 20:16:19 +0100
Subject: Issue #9993: When the source and destination are on different
 filesystems, and the source is a symlink, shutil.move() now recreates a
 symlink on the destination instead of copying the file contents. Patch by
 Jonathan Niehof and Hynek Schlawack.

---
 Doc/library/shutil.rst  |  7 ++++++-
 Lib/shutil.py           | 11 +++++++++--
 Lib/test/test_shutil.py | 43 +++++++++++++++++++++++++++++++++++++++++++
 Misc/ACKS               |  1 +
 Misc/NEWS               |  5 +++++
 5 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/Doc/library/shutil.rst b/Doc/library/shutil.rst
index 45be0e5..9e8784b 100644
--- a/Doc/library/shutil.rst
+++ b/Doc/library/shutil.rst
@@ -196,7 +196,12 @@ Directory and files operations
 
    If the destination is on the current filesystem, then :func:`os.rename` is
    used.  Otherwise, *src* is copied (using :func:`copy2`) to *dst* and then
-   removed.
+   removed. In case of symlinks, a new symlink pointing to the target of *src*
+   will be created in or as *dst* and *src* will be removed.
+
+   .. versionchanged:: 3.3
+      Added explicit symlink handling for foreign filesystems, thus adapting
+      it to the behavior of GNU's :program:`mv`.
 
 .. function:: disk_usage(path)
 
diff --git a/Lib/shutil.py b/Lib/shutil.py
index 95bebb8..5f69fb7 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -356,7 +356,10 @@ def move(src, dst):
     overwritten depending on os.rename() semantics.
 
     If the destination is on our current filesystem, then rename() is used.
-    Otherwise, src is copied to the destination and then removed.
+    Otherwise, src is copied to the destination and then removed. Symlinks are
+    recreated under the new name if os.rename() fails because of cross
+    filesystem renames.
+
     A lot more could be done here...  A look at a mv.c shows a lot of
     the issues this implementation glosses over.
 
@@ -375,7 +378,11 @@ def move(src, dst):
     try:
         os.rename(src, real_dst)
     except OSError:
-        if os.path.isdir(src):
+        if os.path.islink(src):
+            linkto = os.readlink(src)
+            os.symlink(linkto, real_dst)
+            os.unlink(src)
+        elif os.path.isdir(src):
             if _destinsrc(src, dst):
                 raise Error("Cannot move a directory '%s' into itself '%s'." % (src, dst))
             copytree(src, real_dst, symlinks=True)
diff --git a/Lib/test/test_shutil.py b/Lib/test/test_shutil.py
index a750166..c72bac2 100644
--- a/Lib/test/test_shutil.py
+++ b/Lib/test/test_shutil.py
@@ -1104,6 +1104,49 @@ class TestMove(unittest.TestCase):
         finally:
             shutil.rmtree(TESTFN, ignore_errors=True)
 
+    @support.skip_unless_symlink
+    @mock_rename
+    def test_move_file_symlink(self):
+        dst = os.path.join(self.src_dir, 'bar')
+        os.symlink(self.src_file, dst)
+        shutil.move(dst, self.dst_file)
+        self.assertTrue(os.path.islink(self.dst_file))
+        self.assertTrue(os.path.samefile(self.src_file, self.dst_file))
+
+    @support.skip_unless_symlink
+    @mock_rename
+    def test_move_file_symlink_to_dir(self):
+        filename = "bar"
+        dst = os.path.join(self.src_dir, filename)
+        os.symlink(self.src_file, dst)
+        shutil.move(dst, self.dst_dir)
+        final_link = os.path.join(self.dst_dir, filename)
+        self.assertTrue(os.path.islink(final_link))
+        self.assertTrue(os.path.samefile(self.src_file, final_link))
+
+    @support.skip_unless_symlink
+    @mock_rename
+    def test_move_dangling_symlink(self):
+        src = os.path.join(self.src_dir, 'baz')
+        dst = os.path.join(self.src_dir, 'bar')
+        os.symlink(src, dst)
+        dst_link = os.path.join(self.dst_dir, 'quux')
+        shutil.move(dst, dst_link)
+        self.assertTrue(os.path.islink(dst_link))
+        self.assertEqual(os.path.realpath(src), os.path.realpath(dst_link))
+
+    @support.skip_unless_symlink
+    @mock_rename
+    def test_move_dir_symlink(self):
+        src = os.path.join(self.src_dir, 'baz')
+        dst = os.path.join(self.src_dir, 'bar')
+        os.mkdir(src)
+        os.symlink(src, dst)
+        dst_link = os.path.join(self.dst_dir, 'quux')
+        shutil.move(dst, dst_link)
+        self.assertTrue(os.path.islink(dst_link))
+        self.assertTrue(os.path.samefile(src, dst_link))
+
 
 class TestCopyFile(unittest.TestCase):
 
diff --git a/Misc/ACKS b/Misc/ACKS
index 12f4b49..4a7dd11 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -707,6 +707,7 @@ Max Neunhöffer
 George Neville-Neil
 Johannes Nicolai
 Samuel Nicolary
+Jonathan Niehof
 Gustavo Niemeyer
 Oscar Nierstrasz
 Hrvoje Niksic
diff --git a/Misc/NEWS b/Misc/NEWS
index 47fc5e9..274465a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -422,6 +422,11 @@ Core and Builtins
 Library
 -------
 
+- Issue #9993: When the source and destination are on different filesystems,
+  and the source is a symlink, shutil.move() now recreates a symlink on the
+  destination instead of copying the file contents.  Patch by Jonathan Niehof
+  and Hynek Schlawack.
+
 - Issue #12926: Fix a bug in tarfile's link extraction.
 
 - Issue #13696: Fix the 302 Relative URL Redirection problem.
-- 
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