Add get local schema version to the C-API

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Enhancements
 * On Windows devices Device Sync will additionally look up SSL certificates in the Windows Trusted Root Certification Authorities certificate store when establishing a connection. (PR [#7882](https://github.com/realm/realm-core/pull/7882))
 * Updated the return type of `LogCategory::get_category_names()` from `std::vector<const char*>` to `std::vector<std::string_view>`. ([PR #7879](https://github.com/realm/realm-core/pull/7879))
+* Added `realm_get_persisted_schema_version` for reading the version of the schema currently stored locally. (PR [#7873](https://github.com/realm/realm-core/pull/7873))
 
 ### Fixed
 * <How do the end-user experience this issue? what was the impact?> ([#????](https://github.com/realm/realm-core/issues/????), since v?.?.?)
@@ -24,7 +25,6 @@
 # 14.10.4 Release notes
 
 ### Enhancements
-* None.
 
 ### Fixed
 * When a public name is defined on a property, calling `realm::Results::sort()` or `realm::Results::distinct()` with the internal name could throw an error like `Cannot sort on key path 'NAME': property 'PersonObject.NAME' does not exist`. ([realm/realm-js#6779](https://github.com/realm/realm-js/issues/6779), since v12.12.0)

src/realm.h

@@ -1241,6 +1241,11 @@ RLM_API realm_schema_t* realm_get_schema(const realm_t*);
  */
 RLM_API uint64_t realm_get_schema_version(const realm_t* realm);
 
+/**
+ * Get the schema version for this realm at the path.
+ */
+RLM_API uint64_t realm_get_persisted_schema_version(const realm_config_t* config);
+
 /**
  * Update the schema of an open realm.
  *

src/realm/object-store/c_api/schema.cpp

@@ -55,6 +55,23 @@ RLM_API uint64_t realm_get_schema_version(const realm_t* realm)
     return rlm->schema_version();
 }
 
+RLM_API uint64_t realm_get_persisted_schema_version(const realm_config_t* config)
+{
+    auto conf = RealmConfig();
+    conf.schema_version = ObjectStore::NotVersioned;
+    conf.path = config->path;
+    conf.encryption_key = config->encryption_key;
+
+    if (config->sync_config) {
+        conf.sync_config = nullptr;
+        conf.force_sync_history = true;
+    }
+
+    auto realm = Realm::get_shared_realm(conf);
+    uint64_t version = ObjectStore::get_schema_version(realm->read_group());
+    return version;
+}
+
 RLM_API bool realm_schema_validate(const realm_schema_t* schema, uint64_t validation_mode)
 {
     return wrap_err([&]() {

test/object-store/c_api/c_api.cpp

@@ -1287,6 +1287,9 @@ TEST_CASE("C API - schema", "[c_api]") {
         realm_config_set_schema_version(config.get(), 0);
         realm_config_set_schema(config.get(), schema.get());
 
+        // no local schema version yet
+        REQUIRE(realm_get_persisted_schema_version(config.get()) == (uint64_t)-1);
+
         SECTION("error on open") {
             {
                 std::ofstream o(test_file_2.path.c_str());
@@ -1304,6 +1307,7 @@ TEST_CASE("C API - schema", "[c_api]") {
             realm_config_set_data_initialization_function(config.get(), initialize_data, &userdata, nullptr);
             auto realm = cptr_checked(realm_open(config.get()));
             CHECK(userdata.num_initializations == 1);
+            REQUIRE(realm_get_persisted_schema_version(config.get()) == 0);
         }
 
         SECTION("data initialization callback error") {
@@ -1323,6 +1327,7 @@ TEST_CASE("C API - schema", "[c_api]") {
             realm_config_set_migration_function(config.get(), migrate_schema, &userdata, nullptr);
             auto realm = cptr_checked(realm_open(config.get()));
             CHECK(userdata.num_migrations == 0);
+            REQUIRE(realm_get_persisted_schema_version(config.get()) == 0);
             realm.reset();
 
             auto config2 = cptr(realm_config_new());
@@ -1334,6 +1339,7 @@ TEST_CASE("C API - schema", "[c_api]") {
             realm_config_set_migration_function(config2.get(), migrate_schema, &userdata, nullptr);
             auto realm2 = cptr_checked(realm_open(config2.get()));
             CHECK(userdata.num_migrations == 1);
+            REQUIRE(realm_get_persisted_schema_version(config2.get()) == 999);
         }
 
         SECTION("migrate schema and delete old table") {
@@ -5869,6 +5875,7 @@ TEST_CASE("C API - async_open", "[sync][pbs][c_api]") {
         realm_config_set_path(config, test_config.path.c_str());
         realm_config_set_sync_config(config, sync_config);
         realm_config_set_schema_version(config, 1);
+
         realm_async_open_task_t* task = realm_open_synchronized(config);
         REQUIRE(task);
         Userdata userdata;