I don't want to pretend that I know all the answers, but I can try to share what I know.

Provide quick-start examples for common workflows (e.g. by refering the tools docs)

You could just point to each tool's documentation, see my other comment.

• Why Not Just Share Tool Configs?
  If the goal is to standardize linting, why bundle configurations with CMake integration instead of distributing standalone configs (e.g., .clang-format, flake8.ini) that developers could adopt via other tools like pre-commit?

I think it's just easier, especially for the ROS 2 core. And, for other packages, I think the tools matter more than their default configuration file, since that often depends on preferences.

Also, you can run these tools yourself through the CLI, so they can be integrated into pre-commit hooks.

• Abstraction Tradeoffs
  While CMake integration benefits some workflows, it adds a layer that complicates debugging or customization for others. For example, developers using pre-commit might see ament_lint as more of a burden.

With ament_lint tools, the linter is wrapped into an ament_$linter CLI tool, which is then wrapped in CMake (ament_cmake_$linter) or called in a minimal Python file that then becomes a "normal" test, for example: https://github.com/ros2/ros2_tracing/blob/rolling/tracetools_trace/test/test_mypy.py. It is definitely just one approach, and other people have also pointed this out before: linters are usually separate from tests. And using standalone linters often makes setting up/maintaining pre-commit hooks easier.

• Could ament_lint focus on integration while decoupling from configuration?

Possibly, but there hasn't been a good reason to do so yet, or at least a reason that would make the additional complexity/maintenance worth it.

• ROS Core Team’s Reasoning, e.g:
  Ament_lint is the officially supported ROS 2 solution for linting because it ...

The answer to this is probably partly historical. (As an aside, you might wonder: "why is it called "ament?" It's called ament because the ROS 1 equivalent(ish) of this toolset/buildsystem layer was called catkin, another name for the same flower. But why was that called "catkin?" It goes on and on 😄)

I wouldn't necessarily say it's the "officially supported ROS 2 solution for lining;" it's just the most common/most well-integrated linting solution we have. As for why that is, I'd say ROS 2 converged to this solution because of what I mentioned above. Overall, given that ROS 2 is made up of a bunch of repos, it's easier to set up linters as normal tests instead of commit hooks.

Thanks for this detailed reply :).

I'm struggling a bit to write a good summary for these thoughts.
E.g. something like: Ament_lint is for you if you want xyz, you better not use ament_lint if you want xyz. Do you have a suggestion?

I think it's mainly because I don't understand the point of ament_lint. I understand that it's convenient for some developers to have the cmake integration, but I think many developers would also like the ability to apply the Ros core coding styles via linters without being forced to maintain their own configuration and/or use ament_lint. Personally, for example, I would just use pre-commit and run the pure linters. Maybe we can think about providing a pre-commit configruation that ros2 users can use as alternatives to the wrapped linters?. Am I missing something with this approach?

I don't think there's any deep reason for the way it is. It's just one solution, and it's the one we have. It's used by the ROS 2 core, and it can be used by other users if they want to use it.

In some cases, the ament_[cmake_]* wrapper also makes sure to create a standard xUnit result file:

• ament_lint/ament_cmake_uncrustify/cmake/ament_uncrustify.cmake

  Lines 54 to 55 in 1e737ea

  	set(result_file "${AMENT_TEST_RESULTS_DIR}/${PROJECT_NAME}/${ARG_TESTNAME}.xunit.xml")
  	set(cmd "${ament_uncrustify_BIN}" "--xunit-file" "${result_file}")

• ament_lint/ament_uncrustify/ament_uncrustify/main.py

  Lines 216 to 233 in 1e737ea

  	# generate xunit file
  	if args.xunit_file:
  	folder_name = os.path.basename(os.path.dirname(args.xunit_file))
  	file_name = os.path.basename(args.xunit_file)
  	suffix = '.xml'
  	if file_name.endswith(suffix):
  	file_name = file_name[0:-len(suffix)]
  	suffix = '.xunit'
  	if file_name.endswith(suffix):
  	file_name = file_name[0:-len(suffix)]
  	testname = '%s.%s' % (folder_name, file_name)
  	xml = get_xunit_content(report, testname, time.time() - start_time)
  	path = os.path.dirname(os.path.abspath(args.xunit_file))
  	if not os.path.exists(path):
  	os.makedirs(path)
  	with open(args.xunit_file, 'w') as f:
  	f.write(xml)

but, again, this is because these tools are primarily used through tests (see test_mypy.py in my comment above), which a lot of people don't like, even if you can run ament_mypy directly in a terminal (or in CI). You could mention that.

Maybe we can think about providing a pre-commit configruation that ros2 users can use as alternatives to the wrapped linters?. Am I missing something with this approach?

I think that's probably outside of the scope of this repo, but people can do it if they want (and I know some have done it). One reason it's not done for the ROS 2 core itself is that there are so many repos and it would be annoying to set up hooks and maintain them.

but I think many developers would also like the ability to apply the Ros core coding styles via linters without being forced to maintain their own configuration and/or use ament_lint.

I mean, you could just use the configuration file used by the corresponding ament_* tool, e.g.:

• ament_flake8: https://github.com/ament/ament_lint/blob/rolling/ament_flake8/ament_flake8/configuration/ament_flake8.ini
• ament_mypy: https://github.com/ament/ament_lint/blob/rolling/ament_mypy/ament_mypy/configuration/ament_mypy.ini
• ament_uncrustify: https://github.com/ament/ament_lint/blob/rolling/ament_uncrustify/ament_uncrustify/configuration/ament_code_style_0_78.cfg

You could fetch these via curl or whatever.