[3.9] bpo-43219: shutil.copyfile, raise a less confusing exception instead of IsADirectoryError (GH-27049) (GH-27082)

Fixes the misleading IsADirectoryError to be FileNotFoundError.
(cherry picked from commit 248173cc0483a9ad9261353302f1234cf9eb2ebe)


Co-authored-by: andrei kulakov <andrei.avk@gmail.com>

Automerge-Triggered-By: GH:gpshead

1 files changed, 29 insertions, 21 deletions

diff --git a/Lib/shutil.py b/Lib/shutil.py
index 5cb796e800..08384cf92b 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -261,28 +261,36 @@ def copyfile(src, dst, *, follow_symlinks=True):
     if not follow_symlinks and _islink(src):
         os.symlink(os.readlink(src), dst)
     else:
-        with open(src, 'rb') as fsrc, open(dst, 'wb') as fdst:
-            # macOS
-            if _HAS_FCOPYFILE:
-                try:
-                    _fastcopy_fcopyfile(fsrc, fdst, posix._COPYFILE_DATA)
-                    return dst
-                except _GiveupOnFastCopy:
-                    pass
-            # Linux
-            elif _USE_CP_SENDFILE:
-                try:
-                    _fastcopy_sendfile(fsrc, fdst)
+        try:
+            with open(src, 'rb') as fsrc, open(dst, 'wb') as fdst:
+                # macOS
+                if _HAS_FCOPYFILE:
+                    try:
+                        _fastcopy_fcopyfile(fsrc, fdst, posix._COPYFILE_DATA)
+                        return dst
+                    except _GiveupOnFastCopy:
+                        pass
+                # Linux
+                elif _USE_CP_SENDFILE:
+                    try:
+                        _fastcopy_sendfile(fsrc, fdst)
+                        return dst
+                    except _GiveupOnFastCopy:
+                        pass
+                # Windows, see:
+                # https://github.com/python/cpython/pull/7160#discussion_r195405230
+                elif _WINDOWS and file_size > 0:
+                    _copyfileobj_readinto(fsrc, fdst, min(file_size, COPY_BUFSIZE))
                     return dst
-                except _GiveupOnFastCopy:
-                    pass
-            # Windows, see:
-            # https://github.com/python/cpython/pull/7160#discussion_r195405230
-            elif _WINDOWS and file_size > 0:
-                _copyfileobj_readinto(fsrc, fdst, min(file_size, COPY_BUFSIZE))
-                return dst
-
-            copyfileobj(fsrc, fdst)
+
+                copyfileobj(fsrc, fdst)
+
+        # Issue 43219, raise a less confusing exception
+        except IsADirectoryError as e:
+            if os.path.exists(dst):
+                raise
+            else:
+                raise FileNotFoundError(f'Directory does not exist: {dst}') from e
 
     return dst