mcap_vendor: Update to the latest release (v2.1.1)

[MichaelOrlov]

Description

• This PR updates mcap_vendor package to refer to the latest mcap/cpp v2.1.1 release

• Full changelog can be found here foxglove/mcap@releases/cpp/v1.4.0...releases/cpp/v2.1.1

Fixes # N/A

Is this user-facing behavior change?

No.

Did you use Generative AI?

No.

Additional Information

N/A

[MichaelOrlov]

Pulls: #2317
Gist: https://gist.githubusercontent.com/MichaelOrlov/bff5a3356bbc6d369e108393d2a7c3fe/raw/df901d96c4f77e2309c28df1a58961069a1d3496/ros2.repos
BUILD args: --packages-above-and-dependencies mcap_vendor rosbag2_transport rosbag2_tests ros2_bag
TEST args: --packages-above mcap_vendor rosbag2_transport rosbag2_tests ros2_bag
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18013

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[MichaelOrlov]

@mjcarroll it doesn't fly 😞
There is some breakage since mcap/cpp/v2.0.2, which is causing our tests to fail.
For some reason, the mcap reader doesn't return channel objects with zero messages.
The last working version is mcap/cpp/v2.0.1

cc: @james-rms

[james-rms]

👍 I can take a look.

[MichaelOrlov]

@james-rms I would appreciate your help here.
I've made a preliminary analysis and pushed a simple reproducer to the branch.

The failing test is get_metadata_include_topics_with_zero_messages
The test passes with bags recorded with the previous versions (v2.0.1) of the MCAP cpp. However, it fails with the (v2.0.2) of the MCAP cpp. Seems the newer versions of the MCAP cpp writer do not write topics with zero messages? I also noticed that message definition for the "std_msgs/msg/String" type is missing in the new version of the bag.
It turns out that breakage was introduced in the foxglove/mcap#1381
We are getting a failure in test becase the mcap_reader_->channels() returns an empty range here

rosbag2/rosbag2_storage_mcap/src/mcap_storage.cpp

Lines 466 to 469 in 403540e

	// Build a list of topic information along with per-topic message counts
	metadata_.topics_with_message_count.clear();
	for (const auto & [channel_id, channel_ptr] : mcap_reader_->channels()) {
	const mcap::Channel & channel = *channel_ptr;

But the problem is in the mcap writer not reader.

[james-rms]

@MichaelOrlov can you speak to why ROS2 needs topics in bags that have no messages in them? what does a topic with no messages even mean in context?

[james-rms]

I ask because I'm happy to change that test to not test for that, but I want to double check that it's OK.

[jtbandes]

Suggested change

	# URL https://github.com/foxglove/mcap/archive/refs/tags/releases/cpp/v2.0.1.tar.gz
	# URL_HASH SHA1=af844741032eacc9e39527e2715d34baa44cc3b2 # v2.0.1
	URL https://github.com/foxglove/mcap/archive/refs/tags/releases/cpp/v2.0.2.tar.gz
	URL_HASH SHA1=8e62e3e9b07b7f625932571bafaf1b7666b3c487 # v2.0.2
	URL https://github.com/foxglove/mcap/archive/refs/tags/releases/cpp/v2.1.2.tar.gz
	URL_HASH SHA1=0e36ae304c46158ca64d1eede5fc9cb1199ca5a5 # v2.1.2

[MichaelOrlov]

@MichaelOrlov can you speak to why ROS2 needs topics in bags that have no messages in them? what does a topic with no messages even mean in context?

That way, we know the Recorder originally discovered the topic and subscribed to it.
The messages may be lost during recording or not published at all. When we create a new subscription (mcap channel), we also store metadata about this subscription, such as QoS settings and message definition.
This metadata is very useful for triaging why there are no messages in the recording.

[clalancette]

I've opened up foxglove/mcap#1526 , which fixes the failing test here.