fix: ROSBag detects the ROS release by default (release="auto")

src/machinevisiontoolbox/Sources.py

@@ -2994,7 +2994,7 @@ class ROSBag(ImageSource):
 
     :param filename: path to a ``.bag`` file, or an ``http(s)://`` URL
     :type filename: str or Path
-    :param release: ROS release name (or unique substring), e.g. ``"noetic"``, defaults to ``"ROS1_NOETIC"``; controls the message definitions used to parse the bag file
+    :param release: ROS release (distribution) whose message definitions are used to parse the bag file, a name or unique substring such as ``"noetic"`` or ``"humble"``, or ``"auto"`` to detect it, defaults to ``"auto"``
     :type release: str
     :param topicfilter: only yield messages from this topic or list of topics;
         ``None`` accepts all topics
@@ -3095,12 +3095,20 @@ class ROSBag(ImageSource):
         referenced by their bare name, e.g. ``ROSBag("forest.bag")``.
 
     .. note::
-        The ``release`` argument controls the ROS message definitions used to
-        parse the bag file.  This is important because message definitions can
-        change between ROS releases, and using the wrong definitions can lead to
-        incorrect parsing of the data.  The ``release`` string is matched
-        case-insensitively against the member names of :class:`~rosbags.typesys.Stores`,
-        so short names such as ``"noetic"`` or ``"humble"`` are accepted in addition to the full enum name (e.g. ``"ROS1_NOETIC"``).
+        The ``release`` argument selects the ROS release (distribution) whose
+        message definitions are used to parse the bag file.  Message definitions
+        can change between releases, and using the wrong ones can lead to
+        incorrect parsing of the data.
+
+        The default ``"auto"`` tries the known releases on the first message of the
+        bag and keeps the first that decodes it, for both ROS 1 and ROS 2 (CDR)
+        encoded messages.  The choice is then available as the ``release``
+        attribute.  Pass ``verbose=True`` to see what was tried.
+
+        Alternatively name a release.  The string is matched case-insensitively
+        against the member names of :class:`~rosbags.typesys.Stores`, so short names
+        such as ``"noetic"`` or ``"humble"`` are accepted in addition to the full
+        enum name (e.g. ``"ROS1_NOETIC"``).
 
     """
 
@@ -3115,7 +3123,7 @@ class ROSBag(ImageSource):
     def __init__(
         self,
         filename: str,
-        release: str = "ROS1_NOETIC",
+        release: str = "auto",
         topicfilter: str | list[str] | None = None,
         msgfilter: str | list[str] | None = "Image",
         dtype: np.dtype | str | dict | None = None,
@@ -3530,7 +3538,8 @@ def _autodetect_typestore(self, rawdata: bytes, msgtype: str) -> bool:
                 store.deserialize_ros1(raw, msgtype)
                 self.typestore = store
                 self.release = name
-                print(f"  auto-detect: {name} (ros1 encoding)")
+                if self.verbose:
+                    print(f"  auto-detect: {name} (ros1 encoding)")
                 return True
             except (*_LENGTH_ERRORS, KeyError, UnicodeDecodeError, struct.error) as e:
                 # wrong store, or the message is the wrong length for it
@@ -3562,7 +3571,8 @@ def _autodetect_typestore(self, rawdata: bytes, msgtype: str) -> bool:
                 self.typestore = store
                 self.release = name
                 self._is_ros2 = True  # use CDR for all subsequent messages
-                print(f"  auto-detect: {name} (CDR encoding)")
+                if self.verbose:
+                    print(f"  auto-detect: {name} (CDR encoding)")
                 return True
             except (
                 *_LENGTH_ERRORS,

tests/test_ros_release_auto.py

@@ -0,0 +1,82 @@
+"""ROSBag detects the ROS release by default (``release="auto"``).
+
+``bagtool --release`` already defaulted to ``"auto"``; the ``ROSBag`` class defaulted to
+``"ROS1_NOETIC"``, which cannot read ROS 2 (CDR) messages.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import numpy as np
+import pytest
+
+pytest.importorskip("rosbags")
+
+from machinevisiontoolbox import ROSBag
+
+DATA = Path(__file__).parent / "data"
+ROS1_BAG = DATA / "test_ros1.bag"
+ROS2_BAG = DATA / "test_ros2"
+
+# (bag, a release that is known to be right for it)
+BAGS = [(ROS1_BAG, "noetic"), (ROS2_BAG, "humble")]
+
+
+def _need(bag: Path) -> None:
+    if not bag.exists():
+        pytest.skip(f"fixture {bag.name} not generated")
+
+
+def test_default_release_is_auto():
+    _need(ROS1_BAG)
+    assert ROSBag(str(ROS1_BAG)).release == "auto"
+
+
+@pytest.mark.parametrize("bag, release", BAGS)
+def test_default_reads_the_same_images_as_the_right_release(bag, release):
+    _need(bag)
+    auto = list(ROSBag(str(bag)))
+    explicit = list(ROSBag(str(bag), release=release))
+
+    assert len(auto) == len(explicit) > 0
+    for a, e in zip(auto, explicit):
+        assert a.topic == e.topic and a.timestamp == e.timestamp
+        np.testing.assert_array_equal(a.array, e.array)
+
+
+@pytest.mark.parametrize("bag, release", BAGS)
+def test_detected_release_is_reported(bag, release):
+    _need(bag)
+    reader = ROSBag(str(bag))
+    assert reader.release == "auto"
+    next(iter(reader))
+    assert reader.release != "auto"
+    assert reader.release.upper().startswith("ROS")
+
+
+@pytest.mark.parametrize("bag, release", BAGS)
+def test_detection_is_quiet_unless_verbose(bag, release, capsys):
+    _need(bag)
+    list(ROSBag(str(bag)))
+    assert "auto-detect" not in capsys.readouterr().out
+
+    list(ROSBag(str(bag), verbose=True))
+    assert "auto-detect" in capsys.readouterr().out
+
+
+def test_an_explicit_release_still_works_and_is_not_changed():
+    _need(ROS1_BAG)
+    reader = ROSBag(str(ROS1_BAG), release="noetic")
+    assert len(list(reader)) > 0
+    assert reader.release == "noetic"  # nothing was detected, nothing to report
+
+
+def test_default_reads_a_real_ros2_mcap_bag():
+    """The old default, ROS1_NOETIC, raised a SerdeError on this recording."""
+    path = Path(__file__).parent.parent / "bags" / "ros2_bouncing_ball"
+    if not path.exists():
+        pytest.skip("real ROS 2 bag not available")
+    images = list(ROSBag(str(path)))
+    # The bag's metadata claims 132 + 133 images, but its files only hold 39 + 40.
+    assert len(images) == 79