[3.8] bpo-38688, shutil.copytree: consume iterator and create list of entries to prevent infinite recursion (GH-17397)

(cherry picked from commit 9bbcbc9) Co-authored-by: Bruno P. Kinoshita <kinow@users.noreply.github.com>

Author: kinow

Lib/shutil.py

@@ -442,7 +442,7 @@ def _ignore_patterns(path, names):
 def _copytree(entries, src, dst, symlinks, ignore, copy_function,
  ignore_dangling_symlinks, dirs_exist_ok=False):
  if ignore is not None:
- ignored_names = ignore(src, set(os.listdir(src)))
+ ignored_names = ignore(src, {x.name for x in entries})
  else:
  ignored_names = set()
 
@@ -543,11 +543,12 @@ def copytree(src, dst, symlinks=False, ignore=None, copy_function=copy2,
 
  """
  sys.audit("shutil.copytree", src, dst)
- with os.scandir(src) as entries:
- return _copytree(entries=entries, src=src, dst=dst, symlinks=symlinks,
- ignore=ignore, copy_function=copy_function,
- ignore_dangling_symlinks=ignore_dangling_symlinks,
- dirs_exist_ok=dirs_exist_ok)
+ with os.scandir(src) as itr:
+ entries = list(itr)
+ return _copytree(entries=entries, src=src, dst=dst, symlinks=symlinks,
+ ignore=ignore, copy_function=copy_function,
+ ignore_dangling_symlinks=ignore_dangling_symlinks,
+ dirs_exist_ok=dirs_exist_ok)
 
 if hasattr(os.stat_result, 'st_file_attributes'):
  # Special handling for directory junctions to make them behave like

Lib/test/test_shutil.py

@@ -1605,6 +1605,18 @@ def test_copytree_return_value(self):
  rv = shutil.copytree(src_dir, dst_dir)
  self.assertEqual(['foo'], os.listdir(rv))
 
+ def test_copytree_subdirectory(self):
+ # copytree where dst is a subdirectory of src, see Issue 38688
+ base_dir = self.mkdtemp()
+ self.addCleanup(shutil.rmtree, base_dir, ignore_errors=True)
+ src_dir = os.path.join(base_dir, "t", "pg")
+ dst_dir = os.path.join(src_dir, "somevendor", "1.0")
+ os.makedirs(src_dir)
+ src = os.path.join(src_dir, 'pol')
+ write_file(src, 'pol')
+ rv = shutil.copytree(src_dir, dst_dir)
+ self.assertEqual(['pol'], os.listdir(rv))
+
 
 class TestWhich(unittest.TestCase):
 

Misc/NEWS.d/next/Library/2019-11-22-10-45-03.bpo-38668.iKx23z.rst

@@ -0,0 +1,5 @@
+Calling func:`shutil.copytree` to copy a directory tree from one directory
+to another subdirectory resulted in an endless loop and a RecursionError. A
+fix was added to consume an iterator and create the list of the entries to
+be copied, avoiding the recursion for newly created directories. Patch by
+Bruno P. Kinoshita.