Fix crash when removing dictionary key (#7569)

Author: danieltabacaru

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Fixed
 * Fix compilation errors when using command-line `swift build` ([#7587](https://github.com/realm/realm-core/pull/7587), since v14.5.1).
+* Fixed crash when integrating removal of already removed dictionary key ([#7488](https://github.com/realm/realm-core/issues/7488), since v10.0.0).
 
 ### Compatibility
 * Fileformat: Generates files with format v24. Reads and automatically upgrade from fileformat v10. If you want to upgrade from an earlier file format version you will have to use RealmCore v13.x.y or earlier.

src/realm/sync/instruction_applier.cpp

@@ -489,7 +489,7 @@ void InstructionApplier::operator()(const Instruction::Update& instr)
                     }
                 },
                 [&](const Instruction::Payload::Erased&) {
-                    dict.erase(key);
+                    dict.try_erase(key);
                 },
                 [&](const Instruction::Payload::ObjectValue&) {
                     dict.create_and_insert_linked_object(key);

test/test_transform.cpp

@@ -1487,7 +1487,6 @@ TEST(Transform_ArrayInsert_EraseObject)
     client_2.get()->integrate_next_changeset_from(*server);
 }
 
-
 TEST(Transform_ArrayClearVsArrayClear_TimestampBased)
 {
     auto changeset_dump_dir_gen = get_changeset_dump_dir_generator(test_context);
@@ -2081,7 +2080,9 @@ TEST(Transform_Dictionary)
             auto& tr = *c.group;
             auto table = tr.add_table_with_primary_key("class_Table", type_Int, "id");
             table->add_column_dictionary(type_Mixed, "dict");
-            table->create_object_with_primary_key(0);
+            auto obj0 = table->create_object_with_primary_key(0);
+            auto dict = obj0.get_dictionary("dict");
+            dict.insert("key", 42);
             table->create_object_with_primary_key(1);
         });
 
@@ -2096,6 +2097,7 @@ TEST(Transform_Dictionary)
             auto dict0 = obj0.get_dictionary("dict");
             auto dict1 = obj1.get_dictionary("dict");
 
+            dict0.erase("key");
             dict0.insert("a", 123);
             dict0.insert("b", "Hello");
             dict0.insert("c", 45.0);
@@ -2112,6 +2114,7 @@ TEST(Transform_Dictionary)
             auto dict0 = obj0.get_dictionary("dict");
             auto dict1 = obj1.get_dictionary("dict");
 
+            dict0.erase("key");
             dict0.insert("b", "Hello, World!");
             dict0.insert("d", true);
 
@@ -2200,6 +2203,48 @@ TEST(Transform_Set)
     });
 }
 
+TEST(Transform_SetEraseVsSetErase)
+{
+    auto changeset_dump_dir_gen = get_changeset_dump_dir_generator(test_context);
+    auto server = Peer::create_server(test_context, changeset_dump_dir_gen.get());
+    auto client_1 = Peer::create_client(test_context, 2, changeset_dump_dir_gen.get());
+    auto client_2 = Peer::create_client(test_context, 3, changeset_dump_dir_gen.get());
+
+    // Baseline: insert one element in the set ('set' property)
+    client_1->create_schema([](WriteTransaction& tr) {
+        auto t = tr.get_group().add_table_with_primary_key("class_A", type_Int, "pk");
+        t->add_column_set(type_Int, "set");
+        auto obj = t->create_object_with_primary_key(1);
+        auto ss = obj.get_set<Int>("set");
+        ss.insert(42);
+    });
+
+    synchronize(server.get(), {client_1.get(), client_2.get()});
+
+    // Client 1 removes the element from the set
+    client_1->transaction([](Peer& p) {
+        auto ss = p.table("class_A")->begin()->get_set<Int>("set");
+        ss.erase(42);
+    });
+
+    // Client 2 removes the element from the set
+    client_2->transaction([](Peer& p) {
+        auto ss = p.table("class_A")->begin()->get_set<Int>("set");
+        ss.erase(42);
+    });
+
+    synchronize(server.get(), {client_1.get(), client_2.get()});
+
+    // Result: the set is empty
+    ReadTransaction read_server(server->shared_group);
+    ReadTransaction read_client_1(client_1->shared_group);
+    ReadTransaction read_client_2(client_2->shared_group);
+    CHECK(compare_groups(read_server, read_client_1));
+    CHECK(compare_groups(read_server, read_client_2, *test_context.logger));
+    auto table = read_server.get_table("class_A");
+    CHECK(table->begin()->get_set<Int>("set").is_empty());
+}
+
 TEST(Transform_ArrayEraseVsArrayErase)
 {
     // This test case recreates the problem that the above test exposes