GH-73991: Support copying directory symlinks on older Windows (#120807)

Check for `ERROR_INVALID_PARAMETER` when calling `_winapi.CopyFile2()` and
raise `UnsupportedOperation`. In `Path.copy()`, handle this exception and
fall back to the `PathBase.copy()` implementation.

1 files changed, 24 insertions, 3 deletions

diff --git a/Lib/pathlib/_os.py b/Lib/pathlib/_os.py
index bbb019b..61923b5 100644
--- a/Lib/pathlib/_os.py
+++ b/Lib/pathlib/_os.py
@@ -20,6 +20,15 @@ except ImportError:
     _winapi = None
 
 
+__all__ = ["UnsupportedOperation"]
+
+
+class UnsupportedOperation(NotImplementedError):
+    """An exception that is raised when an unsupported operation is attempted.
+    """
+    pass
+
+
 def get_copy_blocksize(infd):
     """Determine blocksize for fastcopying on Linux.
     Hopefully the whole file will be copied in a single call.
@@ -106,18 +115,30 @@ if _winapi and hasattr(_winapi, 'CopyFile2') and hasattr(os.stat_result, 'st_fil
         Copy from one file to another using CopyFile2 (Windows only).
         """
         if follow_symlinks:
-            flags = 0
+            _winapi.CopyFile2(source, target, 0)
         else:
+            # Use COPY_FILE_COPY_SYMLINK to copy a file symlink.
             flags = _winapi.COPY_FILE_COPY_SYMLINK
             try:
                 _winapi.CopyFile2(source, target, flags)
                 return
             except OSError as err:
                 # Check for ERROR_ACCESS_DENIED
-                if err.winerror != 5 or not _is_dirlink(source):
+                if err.winerror == 5 and _is_dirlink(source):
+                    pass
+                else:
                     raise
+
+            # Add COPY_FILE_DIRECTORY to copy a directory symlink.
             flags |= _winapi.COPY_FILE_DIRECTORY
-        _winapi.CopyFile2(source, target, flags)
+            try:
+                _winapi.CopyFile2(source, target, flags)
+            except OSError as err:
+                # Check for ERROR_INVALID_PARAMETER
+                if err.winerror == 87:
+                    raise UnsupportedOperation(err) from None
+                else:
+                    raise
 else:
     copyfile = None