exporter: scrape dicts via items(), not keys() + __getitem__ (KeyError on mutated keys)

objex/exporter.py

@@ -324,9 +324,11 @@ def add_obj(self, obj, refs=0):
                 extra_relationship = frozenset
         # STEP 2 - GET KEYS
         if extra_relationship is dict:
-            keys = obj.keys()
-            key_dst += [('@{}'.format(self._ensure_db_id(key, refs=2)), dict.__getitem__(obj, key))
-                        for key in keys]
+            # dict.items, NOT keys() + __getitem__: a key mutated after insertion
+            # (e.g. openpyxl StyleArray, an array subclass with a content-based
+            # hash) iterates fine but raises KeyError on lookup by key
+            key_dst += [('@{}'.format(self._ensure_db_id(key, refs=2)), value)
+                        for key, value in dict.items(obj)]
         elif extra_relationship in (list, tuple, collections.deque):
             key_dst += enumerate(obj)
         elif extra_relationship in (set, frozenset):

tests/clean_dump_fixture.py

@@ -63,6 +63,19 @@ def __getattribute__(self, name):
         return object.__getattribute__(self, name)
 
 
+class MutableHashKey:
+    """Key whose hash changes when mutated (like openpyxl's StyleArray)."""
+
+    def __init__(self, value=0):
+        self.value = value
+
+    def __hash__(self):
+        return hash(self.value)
+
+    def __eq__(self, other):
+        return isinstance(other, MutableHashKey) and self.value == other.value
+
+
 def closing(a, b=1):
     c = 2
 
@@ -104,6 +117,11 @@ def make_sample_objects():
     weak_set = weakref.WeakSet()
     weak_set.add(slots_c)
 
+    mutated_key = MutableHashKey()
+    mutated_key_dict = {mutated_key: 'stale-bucket'}
+    # hash changed after insertion: iteration works, lookup by key raises KeyError
+    mutated_key.value = 99
+
     global GO_NESTED
     GO_NESTED = types.SimpleNamespace(
         level1=types.SimpleNamespace(
@@ -125,6 +143,7 @@ def make_sample_objects():
         'bound_method': bound_method,
         'generator': generator,
         'weak_set': weak_set,
+        'mutated_key_dict': mutated_key_dict,
         'go_nested': GO_NESTED,
     }
 

tests/test_objex.py

@@ -77,6 +77,19 @@ def __getattribute__(self, name):
         return object.__getattribute__(self, name)
 
 
+class MutableHashKey:
+    """Key whose hash changes when mutated (like openpyxl's StyleArray)."""
+
+    def __init__(self, value=0):
+        self.value = value
+
+    def __hash__(self):
+        return hash(self.value)
+
+    def __eq__(self, other):
+        return isinstance(other, MutableHashKey) and self.value == other.value
+
+
 def closing(a, b=1):
     c = 2
 
@@ -157,6 +170,11 @@ def _make_sample_objects():
         weak_set = weakref.WeakSet()
         weak_set.add(slots_c)
 
+        mutated_key = MutableHashKey()
+        mutated_key_dict = {mutated_key: 'stale-bucket'}
+        # hash changed after insertion: iteration works, lookup by key raises KeyError
+        mutated_key.value = 99
+
         global GO_NESTED
         GO_NESTED = types.SimpleNamespace(
             level1=types.SimpleNamespace(
@@ -178,6 +196,7 @@ def _make_sample_objects():
             'bound_method': bound_method,
             'generator': generator,
             'weak_set': weak_set,
+            'mutated_key_dict': mutated_key_dict,
             'go_nested': GO_NESTED,
         }
 
@@ -320,6 +339,13 @@ def test_dump_graph_uses_resolved_dunder_dict_without_reaccess(self):
         with Reader(str(self.shared_analysis_path)) as reader:
             assert reader.find_type_by_name('MisdirectingGetattribute')
 
+    def test_dump_graph_survives_mutated_dict_keys(self):
+        # dict scrape must use items(), not keys() + __getitem__: a key whose
+        # hash changed after insertion (openpyxl StyleArray in the wild)
+        # iterates fine but raises KeyError on lookup
+        with Reader(str(self.shared_analysis_path)) as reader:
+            assert reader.find_type_by_name('MutableHashKey')
+
     @pytest.mark.slow
     @unittest.skipUnless(hasattr(os, 'fork'), 'requires os.fork')
     def test_spawn_dump_and_wait_dump(self):