Replace copy.deepcopy of the Q object to custom deep copy

Author: rrauenza

polymorphic/query_translate.py

@@ -2,7 +2,6 @@
 PolymorphicQuerySet support functions
 """
 
-import copy
 from collections import deque
 
 from django.apps import apps
@@ -80,6 +79,35 @@ def tree_node_correct_field_specs(my_model, node):
  return potential_q_object
 
 
+def _deepcopy_q_object(q):
+ """
+ Make a deepcopy of a Q-object.
+ """
+
+ def _copy_child(child):
+ if isinstance(child, tuple):
+ return child # tuples are immutable, no need to make a copy.
+ elif isinstance(child, Q):
+ return _deepcopy_q_object(child)
+ else:
+ raise RuntimeError("Unknown child type: %s", type(child))
+
+ children = [_copy_child(c) for c in q.children]
+
+ if hasattr(q, "copy"): # Django 4.2+
+ obj = q.copy()
+ # This assignment of obj.children from children (created above)
+ # is required for test_query_filter_exclude_is_immutable to pass
+ # because somehow the capitalization changed for q_to_reuse?
+ #
+ # assert q_to_reuse.children == untouched_q_object.children
+ # AssertionError: assert [('model2b__f... 'something')] == [('Model2B___... 'something')]
+ obj.children = children
+ else:
+ obj = Q(*children, _connector=q.connector, _negated=q.negated)
+ return obj
+
+
 def translate_polymorphic_filter_definitions_in_args(queryset_model, args, using=DEFAULT_DB_ALIAS):
  """
  Translate the non-keyword argument list for PolymorphicQuerySet.filter()
@@ -92,7 +120,8 @@ def translate_polymorphic_filter_definitions_in_args(queryset_model, args, using
  Returns: modified Q objects
  """
  return [
- translate_polymorphic_Q_object(queryset_model, copy.deepcopy(q), using=using) for q in args
+ translate_polymorphic_Q_object(queryset_model, _deepcopy_q_object(q), using=using)
+ for q in args
  ]
 
 

polymorphic/tests/test_query_translate.py

@@ -0,0 +1,53 @@
+import copy
+import tempfile
+import pickle
+import threading
+
+from django.db.models import Q
+from django.test import TestCase
+
+from polymorphic.tests.models import Bottom, Middle, Top
+from polymorphic.query_translate import translate_polymorphic_filter_definitions_in_args
+
+
+class QueryTranslateTests(TestCase):
+
+ def test_translate_with_not_pickleable_query(self):
+ """
+ In some cases, Django may attacha _thread object to the query and we
+ will get the following when we try to deepcopy inside of 
+ translate_polymorphic_filter_definitions_in_args:
+
+ TypeError: cannot pickle '_thread.lock' object
+
+
+ For this to trigger, we need to somehoe go down this path:
+
+ File "/perfdash/.venv/lib64/python3.12/site-packages/polymorphic/query_translate.py", line 95, in translate_polymorphic_filter_definitions_in_args
+ translate_polymorphic_Q_object(queryset_model, copy.deepcopy(q), using=using) for q in args
+ ^^^^^^^^^^^^^^^^
+ File "/usr/lib64/python3.12/copy.py", line 143, in deepcopy
+ y = copier(memo)
+ ^^^^^^^^^^^^
+ File "/perfdash/.venv/lib64/python3.12/site-packages/django/utils/tree.py", line 53, in __deepcopy__
+ obj.children = copy.deepcopy(self.children, memodict)
+ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ File "/usr/lib64/python3.12/copy.py", line 136, in deepcopy
+ y = copier(x, memo)
+ ^^^^^^^^^^^^^^^
+
+ Internals in Django, somehow we must trigger this tree.py code in django via
+ the deepcopy in order to trigger this.
+
+ """
+
+ with tempfile.TemporaryFile() as fd:
+ # verify this is definitely not pickleable
+ with self.assertRaises(TypeError):
+ pickle.dumps(threading.Lock())
+
+ # I know this doesn't make sense to pass as a Q(), but
+ # I haven't found another way to trigger the copy.deepcopy failing.
+ q = Q(blog__info='blog info') | Q(blog__info=threading.Lock())
+
+ translate_polymorphic_filter_definitions_in_args(Bottom, args=[q])