[TomCC7]

Linear project: Message Encoding Refactor

Problem

Reviewers need the generator, bulk message definitions/packages and transport integration in their respective stack layers.

Solution

Integrated record/replay acceptance above the runtime layer. Normal merge propagation preserves this layer’s parent-relative patch.

Layer 6/8 of native stack #4446. Published HEAD: 055d9983ab8dad1432661630f82bee86819f2d1f. Base: cc/feat/cdr-runtime-cutover. Normal forward commits/merges; existing ancestry and reviews are preserved, with no force push.

Parent-relative git diff (binary lockfile excluded from textual line counts): 8 files changed, 2975 insertions(+).

Layout-repair validation: unchanged namespace-policy test plus generator tests: 41 passed; ownership/project checks: 19 passed; clean source/wheel/sdist/editable installation with Cargo/rustc/CMake/C++ disabled: 1 passed. A fresh backend wheel has api modules/stubs and no stale package initializers. C++/Rust/schema outputs are byte-identical to the pre-layout validated outputs; final built-in generation --check passed. Scoped strict typing and hooks passed. These focused checks are not a complete new-HEAD CI pass.

Production Rust declarations now come from pinned ros2msg 0.5.3 in a normal Cargo build.rs; Python installation only packages its sources and does not invoke Cargo. C++ declaration and CDR field traversal use pinned upstream ROSIDL/FastRTPS templates, with documented strict-bool patches. Python uses rosbags-generated declarations and CDR traversal with scoped malformed-input checks; the separate handwritten wire-layout walker was removed. Default, bounds, ownership and Sequence compatibility adapters remain. PR1 core: ten files including both helpers total 1,380 physical lines versus the original eight-file 1,463. Including maintained typing stubs gives 1,493 -> 1,444, a net 49-line reduction (83 is core-only). Full-stack message_codegen maintained non-test sources total 2,573 lines including stubs; CLI/SDK sources elsewhere are outside that count. Vendored sources and generated/copied artifacts are disclosed separately. Runtime native consumers use the distributed message crate; the redundant four-file Python/Cargo bootstrap (126 lines) was removed. No generator code was hidden in uncounted helpers.

Exact-new-HEAD remote CI is pending; no reruns or manual dispatches were requested for this batch. Historical runs do not verify these commits. Benchmark investigation remains paused, without a waiver or weakened gate.

Complete proposal walkthrough. M20 SDK/access, host multicast and human viewer acceptance remain external; no hardware operation, registry release or merge is claimed.

Replaces closed, unmerged #4364. Original refs/history remain preserved.

Upstream generator contracts, compatibility adapters and maintenance counts.

Namespace repair: five nonempty upstream initializers and two matching typing stubs are relocated to ordinary api modules; the empty parser initializer is omitted. Imports/EmPy templates reference modules directly. Licenses and original upstream source paths/hashes remain recorded, with the relocation and omitted empty file documented in manifests. test_no_init_files is unchanged; no blanket vendor exemption was added. The earlier mypy vendor-discovery boundary remains separate, and first-party strict settings remain enabled. The coauthor policy check remains unresolved; no attribution removal/history rewrite, force push, benchmark gate change, rerun or manual CI dispatch was requested.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

@@                       Coverage Diff                       @@
##           cc/feat/cdr-runtime-cutover    #4370      +/-   ##
===============================================================
- Coverage                        74.07%   74.07%   -0.01%     
===============================================================
  Files                             1746     1746              
  Lines                           177219   177219              
  Branches                         16506    16506              
===============================================================
- Hits                            131280   131279       -1     
- Misses                           42483    42486       +3     
+ Partials                          3456     3454       -2     

Components	Coverage Δ
Tests	84.87% <ø> (+<0.01%)	⬆️

Flag	Coverage Δ
OS-ubuntu-24.04-arm	77.13% <ø> (+0.01%)	⬆️
OS-ubuntu-latest	77.91% <ø> (+<0.01%)	⬆️
Py-3.10	77.66% <ø> (+<0.01%)	⬆️
Py-3.11	77.88% <ø> (+0.01%)	⬆️
Py-3.12	77.89% <ø> (+0.77%)	⬆️

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see 3 files with indirect coverage changes

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