Upgrade cpplint and fix new errors

[azeey]

Summary

Upgrade cpplint to the version found in ign-cmake2. @scpeters and I had discussed using ign-cmake to create a codecheck target, but it looks like we don't directly depend on ign-cmake in the sdf9 branch. So instead, I simply copied cpplint.py from ign-cmake. We might be able to add the codecheck target for sdf10

Test it

sh tools/code_check.sh

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge

[codecov-commenter]

Codecov Report

Merging #680 (6ddc3eb) into sdf9 (e0d77cc) will decrease coverage by 0.00%.
The diff coverage is 90.90%.

❗ Current head 6ddc3eb differs from pull request most recent head f5c8bb3. Consider uploading reports for the commit f5c8bb3 to get more accurate results

@@            Coverage Diff             @@
##             sdf9     #680      +/-   ##
==========================================
- Coverage   86.83%   86.83%   -0.01%     
==========================================
  Files          62       62              
  Lines        9734     9731       -3     
==========================================
- Hits         8453     8450       -3     
  Misses       1281     1281              

Impacted Files	Coverage Δ
include/sdf/Element.hh	100.00% <ø> (ø)
src/Error.cc	100.00% <ø> (ø)
src/FrameSemantics.cc	76.54% <ø> (ø)
src/Joint.cc	92.02% <ø> (ø)
src/Utils.hh	100.00% <ø> (ø)
src/parser.cc	77.63% <ø> (ø)
src/parser_urdf.cc	79.16% <84.61%> (-0.04%)	⬇️
src/Light.cc	88.00% <100.00%> (ø)
src/Link.cc	92.30% <100.00%> (ø)
src/Model.cc	83.54% <100.00%> (ø)
... and 4 more

---

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[chapulina]

So did cpplint actually catch this?

[azeey]

I meant to mention this in the description, but yes, cpplint caught the global string as a runtime/string error:
https://github.com/azeey/sdformat/blob/f5c8bb383fe13d2417f960afb261d626f1cbd40c/tools/cpplint.py#L5455. This helps some with the GSG violations we talked about, but it only works for strings.

[scpeters]

it looks like we don't directly depend on ign-cmake in the sdf9 branch

we depend on ignition-math6, which depends on ignition-cmake2, so I consider it a valid dependency. It would only be used as a build dependency anyway

[azeey]

we depend on ignition-math6, which depends on ignition-cmake2, so I consider it a valid dependency. It would only be used as a build dependency anyway

Okay, I knew about the dependency, but I wasn't sure if it would be possible to build sdformat with just ign-math installed and ign-cmake not installed. If it's okay to add the dependency, I'll do a followup PR that adds the codecheck target.

[scpeters]

we depend on ignition-math6, which depends on ignition-cmake2, so I consider it a valid dependency. It would only be used as a build dependency anyway

Okay, I knew about the dependency, but I wasn't sure if it would be possible to build sdformat with just ign-math installed and ign-cmake not installed. If it's okay to add the dependency, I'll do a followup PR that adds the codecheck target.

cmake fails to find ignition-math6 without ignition-cmake2. I used brew unlink ignition-cmake2 on my macOS machine and then get the following configuration error with sdf9:

-- Looking for ignition-math6-config.cmake - not found
-- 	Missing: Ignition math (libignition-math6-dev)
...
CMake Error at CMakeLists.txt:240 (message):
  -- BUILD ERRORS: These must be resolved before compiling.


CMake Error at CMakeLists.txt:242 (message):
  -- 	Missing: Ignition math (libignition-math6-dev)


CMake Error at CMakeLists.txt:244 (message):
  -- END BUILD ERRORS



CMake Error at CMakeLists.txt:245 (message):
  Errors encountered in build.  Please see the BUILD ERRORS above.

so I think it's safe to add an explicit dependency

[azeey]

Sounds good. I've created a follow up PR #682