Fix pickling of frozen BoxList instances (#344)

AUTHORS.rst

@@ -37,6 +37,7 @@ Code contributions:
 - Jesper Schlegel (jesperschlegel)
 - J vanBemmel (jbemmel)
 - m-janicki
+- Abhinav Maurya (Fire162)
 
 
 Suggestions and bug reporting:

CHANGES.rst

@@ -1,6 +1,8 @@
 Changelog
 =========
 
+* Fixing #344 Frozen BoxList instances cannot be pickled (thanks to Abhinav Maurya)
+
 Version 7.4.1
 -------------
 

box/box_list.py

@@ -35,6 +35,10 @@
 _list_pos_re = re.compile(r"\[(\d+)\]")
 
 
+def _frozen_box_list_method(*args, **kwargs):
+    raise BoxError("BoxList is frozen")
+
+
 class BoxList(list):
     """
     Drop in replacement of list, that converts added objects to Box or BoxList
@@ -58,12 +62,8 @@ def __init__(self, iterable: Iterable | None = None, box_class: type[box.Box] =
                 self.append(x)
         self.box_org_ref = None
         if box_options.get("frozen_box"):
-
-            def frozen(*args, **kwargs):
-                raise BoxError("BoxList is frozen")
-
             for method in ["append", "extend", "insert", "pop", "remove", "reverse", "sort"]:
-                self.__setattr__(method, frozen)
+                self.__setattr__(method, _frozen_box_list_method)
 
     def __getitem__(self, item):
         if self.box_options.get("box_dots") and isinstance(item, str) and item.startswith("["):

test/test_box_list.py

@@ -4,6 +4,7 @@
 
 import json
 import os
+import pickle
 import shutil
 import sys
 import platform
@@ -74,6 +75,54 @@ def test_frozen_list(self):
         bl2[1] = 4
         assert bl2[1] == 4
 
+    def test_frozen_list_pickle(self):
+        for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
+            bl = BoxList([5, 4, 3], frozen_box=True)
+            dumped = pickle.dumps(bl, protocol=protocol)
+            loaded = pickle.loads(dumped)
+            assert loaded == [5, 4, 3]
+            assert loaded.box_options.get("frozen_box") is True
+            with pytest.raises(BoxError):
+                loaded.append(2)
+            with pytest.raises(BoxError):
+                loaded.extend([1])
+            with pytest.raises(BoxError):
+                loaded.pop(0)
+            with pytest.raises(BoxError):
+                loaded.remove(5)
+            with pytest.raises(BoxError):
+                loaded.insert(0, 9)
+            with pytest.raises(BoxError):
+                loaded.reverse()
+            with pytest.raises(BoxError):
+                loaded.sort()
+            with pytest.raises(BoxError):
+                del loaded[0]
+            with pytest.raises(BoxError):
+                loaded[0] = 99
+
+            empty_bl = BoxList([], frozen_box=True)
+            empty_dumped = pickle.dumps(empty_bl, protocol=protocol)
+            empty_loaded = pickle.loads(empty_dumped)
+            assert empty_loaded == []
+            assert empty_loaded.box_options.get("frozen_box") is True
+            with pytest.raises(BoxError):
+                empty_loaded.append(1)
+
+    def test_box_list_pickle(self):
+        for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
+            bl = BoxList([1, 2, 3])
+            dumped = pickle.dumps(bl, protocol=protocol)
+            loaded = pickle.loads(dumped)
+            assert loaded == [1, 2, 3]
+            assert not loaded.box_options.get("frozen_box")
+            loaded.append(4)
+            assert loaded == [1, 2, 3, 4]
+            loaded[0] = 9
+            assert loaded[0] == 9
+            del loaded[0]
+            assert loaded == [2, 3, 4]
+
     def test_box_list_to_json(self):
         bl = BoxList([{"item": 1, "CamelBad": 2}])
         assert json.loads(bl.to_json())[0]["item"] == 1