feat(zenoh): Ros2Connector for outbound ros2:// links (design 053 s09)

[lxsaah]

Stage s09 of docs/design/053-implementation-plan.md: outbound ros2:// (053 §4.2–4.4, §5.1, §6).

The connector

let ros2 = Ros2Connector::new("tcp/192.168.10.5:7447", Ros2Node::new("cell4_gateway").namespace("/cell4"))
    .domain_id(7)
    .register::<Temperature>();
builder.configure::<Temperature>("cell4.temperature", |reg| {
    reg.buffer(BufferCfg::SpmcRing { capacity: 16 }).linked_to("ros2://cell4/temperature");
});

• Ros2Node: a name and a namespace. The namespace is part of the node's identity, not its topics.
• Ros2Connector: domain_id(n) takes precedence; without it the connector reads ROS_DOMAIN_ID, and without that it uses 0. register::<T: RosMessage>() records T's ROS type name, hash and wire format. with_zenoh_config(..) is available, and the connector owns the ros2 scheme. It opens its own session for now; sharing a session with ZenohConnector comes in s11.
• Ros2LinkExt on both link builders: with_depth(n), and with_reliability(Reliability::BestEffort), which is advertised only (see below). Both are parsed once at build time, so an invalid value fails the build.
• What each outbound link does on the wire:
  • its data key is <domain>/<topic>/<type>/<hash>;
  • the node token and one publisher token per link (entity ids 1, 2, …) are declared before the first put;
  • every put carries the 33-byte attachment: a sequence number per publisher starting at 1, a wall-clock timestamp, and the GID of its token;
  • congestion control is Drop, and publications are remote-only, as in s08.

Build-time refusals (criterion 9, outbound rows)

Mistake	Result
register::<T>() on a non-RosMessage type	compile error (trybuild): "NotRos is not a ROS 2 message type", with a hint to derive it. The new #[diagnostic::on_unimplemented] on RosMessage in data-contracts produces this message
Hand-written RosMessage whose Linkable isn't CDR	build() error naming the type
Hand-written malformed hash	build() error naming the type and the hash
Record type never registered	build() error
Non-CDR link codec (linked_to_with(url, Json))	build() error
Topic writer on a ros2:// link	build() error
Bad topic, node name or namespace	build() error, using the profile's rmw rules
ROS_DOMAIN_ID that isn't an integer	build() error. The precedence is tested as a pure function, so tests don't race on the environment
ros2:// with no Ros2Connector	core's existing unregistered-scheme error
Custom serializer	warning, not an error: the documented escape hatch

Inbound ros2:// links fail the build with "not supported yet" until s10.

Design notes

• Reliability isn't sent: reliability() on Zenoh publishers is #[unstable] in 1.10.1, and I didn't enable zenoh/unstable for it. A BEST_EFFORT link advertises best-effort in its token and travels on Zenoh's default reliable path. Zenoh never refuses a match on QoS (053 §6). 053 §5.1 now says this.
• Token building is lean now: mangle and the QoS field are Display adapters, so each token is a single allocation. The golden tests from s07 are unchanged and pass.

Tests

• tests/ros2_outbound.rs, against an in-process router, with a node in domain 7 under /cell4. It checks the node token, publisher tokens for the default QoS (::,10:…) and depth 1 (::,1:…), the data key, that the payload decodes as CDR, and attachments with sequence numbers n then n+1, a sane timestamp, and the GID of the publisher's token. It also covers every refusal above.
• tests/compile_fail.rs (trybuild): the register bound.
• Unit tests: domain precedence and QoS option parsing.
• Live ROS, by hand, with examples/ros2_talker.rs against Jazzy's and Lyrical's rmw_zenohd:
  • ros2 node list shows /aimdb/talker;
  • ros2 topic info -v shows std_msgs/msg/String, the right hash, KEEP_LAST (10), RELIABLE, VOLATILE, and a GID;
  • ros2 topic echo decodes data: aimdb N.

CI

The second commit (7ee775b) adds feat/aimdb-zenoh-connector to ci.yml's pull_request branches, so this PR and later stage PRs run the full matrix instead of a local make check. It stays until you want it reverted.

Run locally: cargo fmt --all -- --check. Before the target-directory cleanup, these had passed: the ros2_outbound tests, the trybuild case and the library tests, plus the live ROS check. CI covers everything else, including clippy on the new code, which I have not run locally.

🤖 Generated with Claude Code