Prevent using message compression mode with mcap storage

ros2bag/ros2bag/verb/record.py

@@ -200,6 +200,11 @@ def main(self, *, args):  # noqa: D102
             return print_error('Invalid choice: Cannot specify compression format '
                                'without a compression mode.')
 
+        if args.compression_mode == 'message' and args.storage == 'mcap':
+            return print_error("Invalid choice: compression_mode 'message' is not supported "
+                               'by the MCAP storage plugin. You can enable chunk compression by '
+                               "setting `compression: 'Zstd'` in storage config")
+
         if args.compression_queue_size < 0:
             return print_error('Compression queue size must be at least 0.')
 

rosbag2_compression/src/rosbag2_compression/sequential_compression_writer.cpp

@@ -217,6 +217,15 @@ void SequentialCompressionWriter::open(
   if (storage_) {
     return;  // The writer already opened.
   }
+  // Note: a better solution was implemented in rosbag2-storage version 0.18+
+  // See MCAPStorage::update_metadata() for details.
+  if (compression_options_.compression_mode == CompressionMode::MESSAGE &&
+    storage_options.storage_id == "mcap")
+  {
+    throw std::runtime_error(
+            "MCAP storage plugin does not support message compression, "
+            "consider using chunk compression by setting `compression: 'Zstd'` in storage config");
+  }
   SequentialWriter::open(storage_options, converter_options);
   setup_compression();
 }