Add support for rosbag version 6 metadata

src/rosbags/rosbag2/metadata.py

@@ -57,3 +57,4 @@ class Metadata(TypedDict):
     compression_mode: str
     topics_with_message_count: list[TopicWithMessageCount]
     files: list[FileInformation]
+    custom_data: dict[str, str]

src/rosbags/rosbag2/reader.py

@@ -65,6 +65,7 @@ class Reader:
         - Version 3: Added compression.
         - Version 4: Added QoS metadata to topics, changed relative file paths
         - Version 5: Added per file metadata
+        - Version 6: Added custom_data dict to metadata
 
     """
 
@@ -92,7 +93,7 @@ class Reader:
 
         try:
             self.metadata: Metadata = dct['rosbag2_bagfile_information']
-            if (ver := self.metadata['version']) > 5:
+            if (ver := self.metadata['version']) > 6:
                 raise ReaderError(f'Rosbag2 version {ver} not supported; please report issue.')
             if storageid := self.metadata['storage_identifier'] != 'sqlite3':
                 raise ReaderError(
@@ -129,6 +130,7 @@ class Reader:
                 raise ReaderError(f'Compression format {cfmt!r} is not supported.')
 
             self.files: list[FileInformation] = self.metadata.get('files', [])[:]
+            self.custom_data: dict[str, str] = self.metadata.get('custom_data', {})
         except KeyError as exc:
             raise ReaderError(f'A metadata key is missing {exc!r}.') from None
 

src/rosbags/rosbag2/writer.py

@@ -85,6 +85,7 @@ class Writer:  # pylint: disable=too-many-instance-attributes
         self.counts: dict[int, int] = {}
         self.conn: Optional[sqlite3.Connection] = None
         self.cursor: Optional[sqlite3.Cursor] = None
+        self.custom_data: dict[str, str] = {}
 
     def set_compression(self, mode: CompressionMode, fmt: CompressionFormat) -> None:
         """Enable compression on bag.
@@ -92,8 +93,8 @@ class Writer:  # pylint: disable=too-many-instance-attributes
         This function has to be called before opening.
 
         Args:
-            mode: Compression mode to use, either 'file' or 'message'
+            mode: Compression mode to use, either 'file' or 'message'.
-            fmt: Compressor to use, currently only 'zstd'
+            fmt: Compressor to use, currently only 'zstd'.
 
         Raises:
             WriterError: Bag already open.
@@ -107,6 +108,21 @@ class Writer:  # pylint: disable=too-many-instance-attributes
         self.compression_format = fmt.name.lower()
         self.compressor = zstandard.ZstdCompressor()
 
+    def set_custom_data(self, key: str, value: str) -> None:
+        """Set key value pair in custom_data.
+
+        Args:
+            key: Key to set.
+            value: Value to set.
+
+        Raises:
+            WriterError: If value has incorrect type.
+
+        """
+        if not isinstance(value, str):
+            raise WriterError(f'Cannot set non-string value {value!r} in custom_data.')
+        self.custom_data[key] = value
+
     def open(self) -> None:
         """Open rosbag2 for writing.
 
@@ -233,7 +249,7 @@ class Writer:  # pylint: disable=too-many-instance-attributes
 
         metadata: dict[str, Metadata] = {
             'rosbag2_bagfile_information': {
-                'version': 5,
+                'version': 6,
                 'storage_identifier': 'sqlite3',
                 'relative_file_paths': [self.dbpath.name],
                 'duration': {
@@ -268,6 +284,7 @@ class Writer:  # pylint: disable=too-many-instance-attributes
                         'message_count': count,
                     },
                 ],
+                'custom_data': self.custom_data,
             },
         }
         with self.metapath.open('w') as metafile:

tests/test_reader.py

@@ -57,7 +57,7 @@ rosbag2_bagfile_information:
 
 METADATA_EMPTY = """
 rosbag2_bagfile_information:
-  version: 4
+  version: 6
   storage_identifier: sqlite3
   relative_file_paths:
     - db.db3
@@ -69,6 +69,16 @@ rosbag2_bagfile_information:
   topics_with_message_count: []
   compression_format: ""
   compression_mode: ""
+  files:
+  - duration:
+      nanoseconds: 0
+    message_count: 0
+    path: db.db3
+    starting_time:
+      nanoseconds_since_epoch: 0
+  custom_data:
+    key1: value1
+    key2: value2
 """
 
 
@@ -146,6 +156,8 @@ def test_empty_bag(tmp_path: Path) -> None:
         assert reader.end_time == 0
         assert reader.duration == 0
         assert not list(reader.messages())
+        assert reader.custom_data['key1'] == 'value1'
+        assert reader.custom_data['key2'] == 'value2'
 
 
 def test_reader(bag: Path) -> None:

tests/test_writer.py

@@ -59,6 +59,15 @@ def test_writer(tmp_path: Path) -> None:
     assert (path / 'compress_message.db3').exists()
     assert size > (path / 'compress_message.db3').stat().st_size
 
+    path = (tmp_path / 'with_custom_data')
+    bag = Writer(path)
+    bag.open()
+    bag.set_custom_data('key1', 'value1')
+    with pytest.raises(WriterError, match='non-string value'):
+        bag.set_custom_data('key1', 42)  # type: ignore
+    bag.close()
+    assert b'key1: value1' in (path / 'metadata.yaml').read_bytes()
+
 
 def test_failure_cases(tmp_path: Path) -> None:
     """Test writer failure cases."""