Replace a deepcopy of the Q object custom deep copy

Author: rrauenza

polymorphic/query_translate.py

@@ -80,6 +80,28 @@ 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()
+        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 +114,7 @@ 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])