Add support for no gravity link

[AzulRadio]

🎉 New feature

Original issue: gazebosim/gz-sim#504

Summary

Add parsing and support for no gravity link when using DartSim engine

For implementation and test details, see gazebosim/gz-sim#2398

Changes in other repo:
gz-physics: gazebosim/gz-physics#633
sdformat: #1410

Test it

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• 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 and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.16%. Comparing base (5fab7a4) to head (52f1d2e).
Report is 2 commits behind head on sdf12.

❗ Current head 52f1d2e differs from pull request most recent head 624bc06. Consider uploading reports for the commit 624bc06 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##            sdf12    #1410      +/-   ##
==========================================
+ Coverage   92.14%   92.16%   +0.02%     
==========================================
  Files          79       79              
  Lines       13126    13267     +141     
==========================================
+ Hits        12095    12228     +133     
- Misses       1031     1039       +8     

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[ahcorde]

Do you mind to update the Python binding too ?

[AzulRadio]

Do you mind to update the Python binding too ?

Sure I'd love to but how do I do that? I looked around but didn't find any docs/codes for this. Can you tell me where I should start?

[ahcorde]

There are two files that you need to modify:

• Include your new method here https://github.com/gazebosim/sdformat/blob/sdf14/python/src/sdf/pyLink.cc
• Include the same test here https://github.com/gazebosim/sdformat/blob/sdf14/python/test/pyLink_TEST.py

[AzulRadio]

There are two files that you need to modify:

These 2 files are only available for sdformat14 but I'm targeting sdformat12 which doesn't have these 2 files. Should I merge this, forward port to 14, and open a separate PR there for python binding, or open another PR on sdformat14 with both cpp and python interface?

[ahcorde]

I opened an issue #1416 to dont forget about the python wrapper

@azeey or @scpeters are you happy with this?

[scpeters]

@azeey or @scpeters are you happy with this?

Yes, this is a great contribution! I've left some small comments and will merge when they are addressed.

[ahcorde]

@scpeters I can see this error on macOS

CMake Error at cmake_install.cmake:41 (file):
  file cannot create directory:
  /usr/local/Cellar/sdformat12/HEAD/lib/cmake/sdformat12-all.  Maybe need
  administrative privileges.

[ahcorde]

friendly ping @scpeters

[azeey]

#1367 needs to be backported to Fortress. I'll go ahead and merge this since the Jenkins macOS build is green.