compare the destination file when copying into a directory

path/__init__.py

@@ -1842,15 +1842,20 @@ def only_newer(copy_func: _CopyFn) -> _CopyFn:
     """
     Wrap a copy function (like shutil.copy2) to return
     the dst if it's newer than the source.
+
+    If dst is a directory, compare against the file with the source's name
+    inside that directory.
     """
 
     @functools.wraps(copy_func)
     def wrapper(src: str, dst: str):
         src_p = Path(src)
         dst_p = Path(dst)
+        if dst_p.is_dir():
+            dst_p = dst_p / src_p.name
         is_newer_dst = dst_p.exists() and dst_p.getmtime() >= src_p.getmtime()
         if is_newer_dst:
-            return dst
+            return dst_p
         return copy_func(src, dst)
 
     return wrapper

tests/test_path.py

@@ -1398,3 +1398,36 @@ def test_ignore(self):
     def test_invalid_handler(self):
         with pytest.raises(ValueError):
             path.Handlers._resolve('raise')
+
+
+@pytest.mark.parametrize('target_mtime', [None, 1000, 3000])
+def test_only_newer_directory(tmp_path, target_mtime):
+    source = Path(tmp_path) / 'source.txt'
+    source.write_text('source')
+    source.utime((2000, 2000))
+    directory = (Path(tmp_path) / 'destination').mkdir()
+    target = directory / source.name
+    if target_mtime is not None:
+        target.write_text('destination')
+        target.utime((target_mtime, target_mtime))
+    directory.utime((4000, 4000))
+
+    result = path.only_newer(shutil.copy2)(source, directory)
+
+    assert result == target
+    expected = 'destination' if target_mtime == 3000 else 'source'
+    assert target.read_text() == expected
+
+
+def test_only_newer_directory_with_newer_file(tmp_path):
+    source = Path(tmp_path) / 'source.txt'
+    source.write_text('source')
+    source.utime((2000, 2000))
+    directory = (Path(tmp_path) / 'destination').mkdir()
+    target = directory / source.name
+    target.write_text('destination')
+    target.utime((3000, 3000))
+    directory.utime((1000, 1000))
+
+    assert path.only_newer(shutil.copy2)(source, directory) == target
+    assert target.read_text() == 'destination'