Duck-type the _copy_writer

Author: barneygale

Lib/pathlib/_abc.py

@@ -561,7 +561,7 @@ def copy(self, target, follow_symlinks=True, dirs_exist_ok=False,
         """
         Recursively copy this file or directory tree to the given destination.
         """
-        if not isinstance(target, ReadablePath):
+        if not hasattr(target, '_copy_writer'):
             target = self.with_segments(target)
 
         # Delegate to the target path's CopyWriter object.
@@ -579,7 +579,7 @@ def copy_into(self, target_dir, *, follow_symlinks=True,
         name = self.name
         if not name:
             raise ValueError(f"{self!r} has an empty name")
-        elif isinstance(target_dir, ReadablePath):
+        elif hasattr(target_dir, '_copy_writer'):
             target = target_dir / name
         else:
             target = self.with_segments(target_dir, name)

Lib/pathlib/_local.py

@@ -1166,7 +1166,7 @@ def move(self, target):
         except TypeError:
             pass
         else:
-            if not isinstance(target, WritablePath):
+            if not hasattr(target, '_copy_writer'):
                 target = self.with_segments(target_str)
             target._copy_writer._ensure_different_file(self)
             try:
@@ -1187,7 +1187,7 @@ def move_into(self, target_dir):
         name = self.name
         if not name:
             raise ValueError(f"{self!r} has an empty name")
-        elif isinstance(target_dir, WritablePath):
+        elif hasattr(target_dir, '_copy_writer'):
             target = target_dir / name
         else:
             target = self.with_segments(target_dir, name)