[3.13] gh-120108: Fix deepcopying of AST trees with .parent attributes (

GH-120114) (#121000)

(cherry picked from commit 42b2c9d)

Lib/test/test_ast.py

@@ -1,5 +1,6 @@
 import ast
 import builtins
+import copy
 import dis
 import enum
 import os
@@ -23,7 +24,7 @@
 from test.support.ast_helper import ASTTestMixin
 
 def to_tuple(t):
- if t is None or isinstance(t, (str, int, complex)) or t is Ellipsis:
+ if t is None or isinstance(t, (str, int, complex, float, bytes)) or t is Ellipsis:
  return t
  elif isinstance(t, list):
  return [to_tuple(e) for e in t]
@@ -971,15 +972,6 @@ def test_no_fields(self):
  x = ast.Sub()
  self.assertEqual(x._fields, ())
 
- def test_pickling(self):
- import pickle
-
- for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
- for ast in (compile(i, "?", "exec", 0x400) for i in exec_tests):
- with self.subTest(ast=ast, protocol=protocol):
- ast2 = pickle.loads(pickle.dumps(ast, protocol))
- self.assertEqual(to_tuple(ast2), to_tuple(ast))
-
  def test_invalid_sum(self):
  pos = dict(lineno=2, col_offset=3)
  m = ast.Module([ast.Expr(ast.expr(**pos), **pos)], [])
@@ -1222,6 +1214,80 @@ def test_none_checks(self) -> None:
  for node, attr, source in tests:
  self.assert_none_check(node, attr, source)
 
+
+class CopyTests(unittest.TestCase):
+ """Test copying and pickling AST nodes."""
+
+ def test_pickling(self):
+ import pickle
+
+ for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
+ for code in exec_tests:
+ with self.subTest(code=code, protocol=protocol):
+ tree = compile(code, "?", "exec", 0x400)
+ ast2 = pickle.loads(pickle.dumps(tree, protocol))
+ self.assertEqual(to_tuple(ast2), to_tuple(tree))
+
+ def test_copy_with_parents(self):
+ # gh-120108
+ code = """
+ ('',)
+ while i < n:
+ if ch == '':
+ ch = format[i]
+ if ch == '':
+ if freplace is None:
+ '' % getattr(object)
+ elif ch == '':
+ if zreplace is None:
+ if hasattr:
+ offset = object.utcoffset()
+ if offset is not None:
+ if offset.days < 0:
+ offset = -offset
+ h = divmod(timedelta(hours=0))
+ if u:
+ zreplace = '' % (sign,)
+ elif s:
+ zreplace = '' % (sign,)
+ else:
+ zreplace = '' % (sign,)
+ elif ch == '':
+ if Zreplace is None:
+ Zreplace = ''
+ if hasattr(object):
+ s = object.tzname()
+ if s is not None:
+ Zreplace = s.replace('')
+ newformat.append(Zreplace)
+ else:
+ push('')
+ else:
+ push(ch)
+
+ """
+ tree = ast.parse(textwrap.dedent(code))
+ for node in ast.walk(tree):
+ for child in ast.iter_child_nodes(node):
+ child.parent = node
+ try:
+ with support.infinite_recursion(200):
+ tree2 = copy.deepcopy(tree)
+ finally:
+ # Singletons like ast.Load() are shared; make sure we don't
+ # leave them mutated after this test.
+ for node in ast.walk(tree):
+ if hasattr(node, "parent"):
+ del node.parent
+
+ for node in ast.walk(tree2):
+ for child in ast.iter_child_nodes(node):
+ if hasattr(child, "parent") and not isinstance(child, (
+ ast.expr_context, ast.boolop, ast.unaryop, ast.cmpop, ast.operator,
+ )):
+ self.assertEqual(to_tuple(child.parent), to_tuple(node))
+
+
 class ASTHelpers_Test(unittest.TestCase):
  maxDiff = None
 

Misc/NEWS.d/next/Library/2024-06-05-08-02-46.gh-issue-120108.4U9BL8.rst

@@ -0,0 +1,2 @@
+Fix calling :func:`copy.deepcopy` on :mod:`ast` trees that have been
+modified to have references to parent nodes. Patch by Jelle Zijlstra.

Parser/asdl_c.py

@@ -1064,17 +1064,22 @@ def visitModule(self, mod):
  return NULL;
  }
 
- PyObject *dict = NULL, *fields = NULL, *remaining_fields = NULL,
- *remaining_dict = NULL, *positional_args = NULL;
+ PyObject *dict = NULL, *fields = NULL, *positional_args = NULL;
  if (PyObject_GetOptionalAttr(self, state->__dict__, &dict) < 0) {
  return NULL;
  }
  PyObject *result = NULL;
  if (dict) {
- // Serialize the fields as positional args if possible, because if we
- // serialize them as a dict, during unpickling they are set only *after*
- // the object is constructed, which will now trigger a DeprecationWarning
- // if the AST type has required fields.
+ // Unpickling (or copying) works as follows:
+ // - Construct the object with only positional arguments
+ // - Set the fields from the dict
+ // We have two constraints:
+ // - We must set all the required fields in the initial constructor call,
+ // or the unpickling or deepcopying of the object will trigger DeprecationWarnings.
+ // - We must not include child nodes in the positional args, because
+ // that may trigger runaway recursion during copying (gh-120108).
+ // To satisfy both constraints, we set all the fields to None in the
+ // initial list of positional args, and then set the fields from the dict.
  if (PyObject_GetOptionalAttr((PyObject*)Py_TYPE(self), state->_fields, &fields) < 0) {
  goto cleanup;
  }
@@ -1084,11 +1089,6 @@ def visitModule(self, mod):
  Py_DECREF(dict);
  goto cleanup;
  }
- remaining_dict = PyDict_Copy(dict);
- Py_DECREF(dict);
- if (!remaining_dict) {
- goto cleanup;
- }
  positional_args = PyList_New(0);
  if (!positional_args) {
  goto cleanup;
@@ -1099,15 +1099,15 @@ def visitModule(self, mod):
  goto cleanup;
  }
  PyObject *value;
- int rc = PyDict_Pop(remaining_dict, name, &value);
+ int rc = PyDict_GetItemRef(dict, name, &value);
  Py_DECREF(name);
  if (rc < 0) {
  goto cleanup;
  }
  if (!value) {
  break;
  }
- rc = PyList_Append(positional_args, value);
+ rc = PyList_Append(positional_args, Py_None);
  Py_DECREF(value);
  if (rc < 0) {
  goto cleanup;
@@ -1117,8 +1117,7 @@ def visitModule(self, mod):
  if (!args_tuple) {
  goto cleanup;
  }
- result = Py_BuildValue("ONO", Py_TYPE(self), args_tuple,
- remaining_dict);
+ result = Py_BuildValue("ONN", Py_TYPE(self), args_tuple, dict);
  }
  else {
  result = Py_BuildValue("O()N", Py_TYPE(self), dict);
@@ -1129,8 +1128,6 @@ def visitModule(self, mod):
  }
 cleanup:
  Py_XDECREF(fields);
- Py_XDECREF(remaining_fields);
- Py_XDECREF(remaining_dict);
  Py_XDECREF(positional_args);
  return result;
 }