json_db: fix StoredDict.__delitem__() to work similarly to .pop()

follow-up https://github.com/spesmilo/electrum/pull/10233 ("jsondb pointers")

electrum/json_db.py

@@ -222,8 +222,11 @@ class StoredDict(dict, BaseStoredObject):
     @locked
     def __delitem__(self, key: _FLEX_KEY) -> None:
         assert isinstance(key, _FLEX_KEY), repr(key)
+        r  = self.get(key, None)
         dict.__delitem__(self, key)
         self.db_remove(key)
+        if isinstance(r, StoredDict):
+            r._parent = None
 
     @locked
     def pop(self, key: _FLEX_KEY, v=_RaiseKeyError) -> Any:

tests/test_jsondb.py

@@ -2,6 +2,7 @@ import contextlib
 import copy
 import traceback
 import json
+from typing import Any
 
 import jsonpatch
 from jsonpatch import JsonPatchException
@@ -88,6 +89,16 @@ class TestJsonpatch(ElectrumTestCase):
             fail_if_leaking_secret(ctx)
 
 
+def pop1_from_dict(d: dict, key: str) -> Any:
+    return d.pop(key)
+
+
+def pop2_from_dict(d: dict, key: str) -> Any:
+    val = d[key]
+    del d[key]
+    return val
+
+
 class TestJsonDB(ElectrumTestCase):
 
     async def test_jsonpatch_replace_after_remove(self):
@@ -109,31 +120,35 @@ class TestJsonDB(ElectrumTestCase):
             data = jpatch.apply(data)
 
     async def test_jsondb_replace_after_remove(self):
-        data = { 'a': {'b': {'c': 0}}, 'd': 3}
+        for pop_from_dict in [pop1_from_dict, pop2_from_dict]:
-        db = JsonDB(repr(data))
+            with self.subTest(pop_from_dict):
-        a = db.get_dict('a')
+                data = { 'a': {'b': {'c': 0}}, 'd': 3}
-        # remove
+                db = JsonDB(repr(data))
-        b = a.pop('b')
+                a = db.get_dict('a')
-        self.assertEqual(len(db.pending_changes), 1)
+                # remove
-        # replace item. this must not been written to db
+                b = pop_from_dict(a, 'b')
-        b['c'] = 42
+                self.assertEqual(len(db.pending_changes), 1)
-        self.assertEqual(len(db.pending_changes), 1)
+                # replace item. this must not been written to db
-        patches = json.loads('[' + ','.join(db.pending_changes) + ']')
+                b['c'] = 42
-        jpatch = jsonpatch.JsonPatch(patches)
+                self.assertEqual(len(db.pending_changes), 1)
-        data = jpatch.apply(data)
+                patches = json.loads('[' + ','.join(db.pending_changes) + ']')
-        self.assertEqual(data, {'a': {}, 'd': 3})
+                jpatch = jsonpatch.JsonPatch(patches)
+                data = jpatch.apply(data)
+                self.assertEqual(data, {'a': {}, 'd': 3})
 
     async def test_jsondb_replace_after_remove_nested(self):
-        data = { 'a': {'b': {'c': 0}}, 'd': 3}
+        for pop_from_dict in [pop1_from_dict, pop2_from_dict]:
-        db = JsonDB(repr(data))
+            with self.subTest(pop_from_dict):
-        # remove
+                data = { 'a': {'b': {'c': 0}}, 'd': 3}
-        a = db.data.pop('a')
+                db = JsonDB(repr(data))
-        self.assertEqual(len(db.pending_changes), 1)
+                # remove
-        b = a['b']
+                a = pop_from_dict(db.data, "a")
-        # replace item. this must not be written to db
+                self.assertEqual(len(db.pending_changes), 1)
-        b['c'] = 42
+                b = a['b']
-        self.assertEqual(len(db.pending_changes), 1)
+                # replace item. this must not be written to db
-        patches = json.loads('[' + ','.join(db.pending_changes) + ']')
+                b['c'] = 42
-        jpatch = jsonpatch.JsonPatch(patches)
+                self.assertEqual(len(db.pending_changes), 1)
-        data = jpatch.apply(data)
+                patches = json.loads('[' + ','.join(db.pending_changes) + ']')
-        self.assertEqual(data, {'d': 3})
+                jpatch = jsonpatch.JsonPatch(patches)
+                data = jpatch.apply(data)
+                self.assertEqual(data, {'d': 3})