Store: actually throw if the macOS application group is too long GH#515

Also throw if empty.

Also use same character limit in error message as noted in docs.

Also actually check the C API call result.

Author: greenrobot-team

objectbox/CHANGELOG.md

@@ -1,5 +1,8 @@
 ## latest
 
+* macOS: throw an error if the `macosApplicationGroup` parameter when opening a `Store` is too long
+  (or empty). [#515](https://github.com/objectbox/objectbox-dart/issues/515#issuecomment-3503022269)
+
 ### Sync
 
 * SyncClient: actually configure Sync filters when passing them to `Sync.client` and related helper

objectbox/lib/src/native/store.dart

@@ -229,21 +229,30 @@ class Store implements Finalizable {
       : _closesNativeStore = true,
         _absoluteDirectoryPath = _safeAbsoluteDirectoryPath(directory) {
     try {
-      if (Platform.isMacOS && macosApplicationGroup != null) {
+      if (macosApplicationGroup != null) {
+        final isGroupEmpty = macosApplicationGroup.isEmpty;
+        // Docs don't explicitly require a trailing slash, so add one if missing
         if (!macosApplicationGroup.endsWith('/')) {
           macosApplicationGroup += '/';
         }
-        if (macosApplicationGroup.length > 20) {
-          ArgumentError.value(macosApplicationGroup, 'macosApplicationGroup',
-              'Must be at most 20 characters long');
+        // The database library would check for length, but refers to 'prefix'
+        // instead of the parameter name used here. So duplicate the checks.
+        if (isGroupEmpty || macosApplicationGroup.length > 20) {
+          throw ArgumentError.value(
+              macosApplicationGroup,
+              'macosApplicationGroup',
+              'Must be at least 1 and at most 19 characters long');
         }
         // This is required to enable additional interprocess communication
         // (IPC) in sandboxed apps (https://developer.apple.com/documentation/xcode/configuring-app-groups),
         // like POSIX semaphores, used by mutexes in the ObjectBox database
         // library. macOS requires that semaphore names are prefixed with an
         // application group ID.
         // See the constructor docs for more details.
-        withNativeString(macosApplicationGroup, C.posix_sem_prefix_set);
+        // Note: calling this on all platforms is fine, it will be a no-op if
+        // not supported.
+        checkObx(
+            withNativeString(macosApplicationGroup, C.posix_sem_prefix_set));
       }
       _checkStoreDirectoryNotOpen();
       final model = Model(modelDefinition.model);

objectbox_test/test/store_test.dart

@@ -290,6 +290,23 @@ void main() {
     Directory('store').deleteSync(recursive: true);
   });
 
+  test('store macOS application group checks', () {
+    // Note: the "store options" test tests a valid value
+    expect(
+        () => Store(getObjectBoxModel(),
+            directory: 'store',
+            macosApplicationGroup:
+                'this-application-group-identifier-is-way-too-long'),
+        throwsA(isArgumentError.having((e) => e.message, 'message',
+            contains('Must be at least 1 and at most 19 characters long'))));
+
+    expect(
+        () => Store(getObjectBoxModel(),
+            directory: 'store', macosApplicationGroup: ''),
+        throwsA(isArgumentError.having((e) => e.message, 'message',
+            contains('Must be at least 1 and at most 19 characters long'))));
+  });
+
   test('store dbFileSize', () {
     final testEnv = TestEnv("db-file-size");
     expect(Store.dbFileSize(testEnv.dbDirPath), isPositive);