Assert powersync_control is called in transactions only

Author: simolus3

crates/core/src/sync/interface.rs

@@ -125,6 +125,8 @@ pub fn register(db: *mut sqlite::sqlite3) -> Result<(), ResultCode> {
         argv: *mut *mut sqlite::value,
     ) -> () {
         let result = (|| -> Result<(), SQLiteError> {
+            debug_assert!(!ctx.db_handle().get_autocommit());
+
             let controller = unsafe { ctx.user_data().cast::<SqlController>().as_mut() }
                 .ok_or_else(|| SQLiteError::from(ResultCode::INTERNAL))?;
 

dart/test/sync_test.dart

@@ -49,8 +49,10 @@ void _syncTests<T>({
   late SyncLinesGoldenTest matcher;
 
   List<Object?> invokeControlRaw(String operation, Object? data) {
+    db.execute('begin');
     final [row] =
         db.select('SELECT powersync_control(?, ?)', [operation, data]);
+    db.execute('commit');
     return jsonDecode(row.columnAt(0));
   }
 
@@ -59,9 +61,7 @@ void _syncTests<T>({
       // Trace through golden matcher
       return matcher.invoke(operation, data);
     } else {
-      final [row] =
-          db.select('SELECT powersync_control(?, ?)', [operation, data]);
-      return jsonDecode(row.columnAt(0));
+      return invokeControlRaw(operation, data);
     }
   }
 

docs/sync.md

@@ -5,6 +5,7 @@ sync line sent from a PowerSync service instance.
 
 After registering the PowerSync extension, this client is available through the `powersync_control`
 function, which takes two arguments: A command (text), and a payload (text, blob, or null).
+The function should always be called in a transaction.
 
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