Copied type_description_interfaces structs (rep2011)

[emersonknapp]

Part of ros2/ros2#1159

Reviewers please see scripts/copy_type_description_generated_sources.bash which creates these copies - the manual changes in this review are

• rosidl_runtime_c/CMakeLists.txt
• rosidl_runtime_c/docs/FEATURES.md
• rosidl_runtime_cpp/CMakeLists.txt
• rosidl_runtime_cpp/docs/FEATURES.md
• scripts/copy_type_description_generated_sources.bash

[clalancette]

Besides the changes inline, I'm wondering if we should add a git hook or github action to check if someone manually changes these files. I'd prefer the git hook (that way it will inform them locally when they are committing), but if we can't make that happen then a github action to check this would be nice.

[emersonknapp]

@clalancette I'm thinking about how a hook could check on this. At the end of the day we don't know where the built code being copied actually came from so it can't be fully proofed against fools or ne'erdowells.

Maybe some "fingerprint" separate file that's also checked in - and that file can be just a big mean warning and one piece of information like the git commit of type_description_interfaces that the generated sources came from

# DO NOT EDIT MANUALLY - managed by scripts/copy_type_description_generated_sources.bash
# INTENTIONALLY CHANGING THIS FILE OUTSIDE THE SCRIPT 
# WILL RESULT IN UNDEFINED BEHAVIOR FOR ALL OF ROS 2 CORE
TYPE_DESCRIPTION_INTERFACES_GIT_COMMIT=deadbeef

And then the git hook could simply verify that this file is also changed alongside changes to any of the copied sources?

[emersonknapp]

Ah - I forgot. git hooks aren't checked in, you can't enforce their use by end users except by extra setup steps asking them to set up hooks for their local clone. The only way to make this policy enforceable is definitely a github action

[emersonknapp]

OK - I've checked in a github action that looks for changed files, and fails immediately if "fingerprint" is changed without sources, or vice versa. If both are changed, then it looks for the latest commit on rcl_interfaces:rolling and checks for equality on the value in the fingerprint.

Cases testing:

• No protected things changed: [test] Touch nonprotected files emersonknapp/rosidl#8
• Fingerprint changed, but not copied sources: [test] Touched fingerprint manually emersonknapp/rosidl#6
• Sources changed, but not fingerprint: [test] Touched a type description file manually emersonknapp/rosidl#7
• Fingerprint and sources changed, not equal value: https://github.com/ros2/rosidl/pull/732/checks?check_run_id=12319035002
• Fingerprint and sources changed, equal value: https://github.com/ros2/rosidl/pull/732/checks?check_run_id=12319175638

[emersonknapp]

OK, second pass. I've changed the fingerprint file to be an output of hashes of the files that got copied. The builtin check here only checks that the fingerprint file changes when the copied sources do, but the big mean warning should be what warns folks off from changing it manually.

Cases testing:

• No protected things changed: [test] Touch nonprotected files emersonknapp/rosidl#8
• Fingerprint changed, but not copied sources: [test] Touched fingerprint manually emersonknapp/rosidl#6
• Sources changed, but not fingerprint: [test] Touched a type description file manually emersonknapp/rosidl#7

[emersonknapp]

Gist: https://gist.githubusercontent.com/emersonknapp/583f883f05c5405351ac612c1c628d1f/raw/5d9dbe9f73ad23684d544bf0ace2955160cf2340/ros2.repos
BUILD args:
TEST args:
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/11701

• Linux
• Linux-aarch64
• Windows

arm failed in infrastructure and auto-triggered rebuild

• Linux-aarch64