do nothing when copying/moving a file to itself (#234)

NEWS

@@ -33,6 +33,7 @@
 * Fix a missing __future__ import in embedart on Python 2.5.
 * Fix ID3 and MPEG-4 tag names for the album-artist field.
 * Fix Unicode encoding of album artist, album type, and label.
+* Fix crash when "copying" an art file that's already in place.
 
 1.0b9
 -----

beets/util/__init__.py

@@ -193,9 +193,12 @@ def _assert_not_exists(path, pathmod=None):
 
 def copy(path, dest, replace=False, pathmod=None):
     """Copy a plain file. Permissions are not copied. If dest already
-    exists, raises an OSError unless replace is True. Paths are
-    translated to system paths before the syscall.
+    exists, raises an OSError unless replace is True. Has no effect if
+    path is the same as dest. Paths are translated to system paths
+    before the syscall.
     """
+    if samefile(path, dest):
+        return
     path = syspath(path)
     dest = syspath(dest)
     _assert_not_exists(dest, pathmod)
@@ -203,9 +206,11 @@ def copy(path, dest, replace=False, pathmod=None):
 
 def move(path, dest, replace=False, pathmod=None):
     """Rename a file. dest may not be a directory. If dest already
-    exists, raises an OSError unless replace is True. Paths are
-    translated to system paths.
+    exists, raises an OSError unless replace is True. Hos no effect if
+    path is the same as dest. Paths are translated to system paths.
     """
+    if samefile(path, dest):
+        return
     path = syspath(path)
     dest = syspath(dest)
     _assert_not_exists(dest, pathmod)

test/test_files.py

@@ -399,7 +399,7 @@ class SoftRemoveTest(unittest.TestCase, _common.ExtraAsserts):
         except OSError:
             self.fail('OSError when removing path')
 
-class SafeMoveCopyTest(unittest.TestCase):
+class SafeMoveCopyTest(unittest.TestCase, _common.ExtraAsserts):
     def setUp(self):
         self.path = os.path.join(_common.RSRC, 'testfile')
         touch(self.path)
@@ -420,9 +420,13 @@ class SafeMoveCopyTest(unittest.TestCase):
 
     def test_successful_move(self):
         util.move(self.path, self.dest)
+        self.assertExists(self.dest)
+        self.assertNotExists(self.path)
 
     def test_successful_copy(self):
         util.copy(self.path, self.dest)
+        self.assertExists(self.dest)
+        self.assertExists(self.path)
 
     def test_unsuccessful_move(self):
         with self.assertRaises(OSError):
@@ -432,6 +436,14 @@ class SafeMoveCopyTest(unittest.TestCase):
         with self.assertRaises(OSError):
             util.copy(self.path, self.otherpath)
 
+    def test_self_move(self):
+        util.move(self.path, self.path)
+        self.assertExists(self.path)
+
+    def test_self_copy(self):
+        util.copy(self.path, self.path)
+        self.assertExists(self.path)
+
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)