tests/test_jsondb.py: add tests that replace a StoredDict element

after its parent has been removed.

Related: #10000

tests/test_jsondb.py

@@ -1,6 +1,7 @@
 import contextlib
 import copy
 import traceback
+import json
 
 import jsonpatch
 from jsonpatch import JsonPatchException
@@ -8,6 +9,7 @@ from jsonpointer import JsonPointerException
 
 from . import ElectrumTestCase
 
+from electrum.json_db import JsonDB
 
 class TestJsonpatch(ElectrumTestCase):
 
@@ -84,3 +86,50 @@ class TestJsonpatch(ElectrumTestCase):
             with self._customAssertRaises(JsonPointerException) as ctx:
                 data2 = jpatch.apply(data1)
             fail_if_leaking_secret(ctx)
+
+
+class TestJsonDB(ElectrumTestCase):
+
+    async def test_jsonpatch_replace_after_remove(self):
+        data = { 'a':{} }
+        # op "add"
+        patches = [{"op": "add", "path": "/a/b", "value": "42"}]
+        jpatch = jsonpatch.JsonPatch(patches)
+        data = jpatch.apply(data)
+        # remove
+        patches = [{"op": "remove", "path": "/a/b"}]
+        jpatch = jsonpatch.JsonPatch(patches)
+        data = jpatch.apply(data)
+        # replace
+        patches = [{"op": "replace", "path": "/a/b", "value": "43"}]
+        jpatch = jsonpatch.JsonPatch(patches)
+        with self.assertRaises(JsonPatchException):
+            data = jpatch.apply(data)
+
+    async def test_jsondb_replace_after_remove(self):
+        data = { 'a': {'b': {'c': 0}}}
+        db = JsonDB(repr(data))
+        a = db.get_dict('a')
+        # remove
+        b = a.pop('b')
+        self.assertEqual(len(db.pending_changes), 1)
+        # replace item. this must not been written to db
+        b['c'] = 42
+        self.assertEqual(len(db.pending_changes), 1)
+        patches = json.loads('[' + ','.join(db.pending_changes) + ']')
+        jpatch = jsonpatch.JsonPatch(patches)
+        data = jpatch.apply(data)
+
+    async def test_jsondb_replace_after_remove_nested(self):
+        data = { 'a': {'b':{'c':0}}}
+        db = JsonDB(repr(data))
+        # remove
+        a = db.data.pop('a')
+        self.assertEqual(len(db.pending_changes), 1)
+        b = a['b']
+        # replace item. this must not be written to db
+        b['c'] = 42
+        self.assertEqual(len(db.pending_changes), 1)
+        patches = json.loads('[' + ','.join(db.pending_changes) + ']')
+        jpatch = jsonpatch.JsonPatch(patches)
+        data = jpatch.apply(data)