Use std::optional instead of nullptr checking

[Shobuj-Paul]

Description

Wrapped scene_transforms_, robot_state_, acm_ and object_types_ in std::optional to handle missing data instead of checking for nullptr.
Fixes #2131

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Attention: Patch coverage is 72.22222% with 25 lines in your changes are missing coverage. Please review.

Project coverage is 42.98%. Comparing base (d962501) to head (39e6839).
Report is 19 commits behind head on main.

Files	Patch %	Lines
moveit_core/planning_scene/src/planning_scene.cpp	70.59%	25 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2454      +/-   ##
==========================================
- Coverage   50.74%   42.98%   -7.76%     
==========================================
  Files         392      692     +300     
  Lines       32553    56332   +23779     
  Branches        0     7274    +7274     
==========================================
+ Hits        16517    24208    +7691     
- Misses      16036    31961   +15925     
- Partials        0      163     +163     

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[sjahr]

Thanks for tackling this! Something is still not working since the tests are complaining. Can you fix that?

[Shobuj-Paul]

Thanks for tackling this! Something is still not working since the tests are complaining. Can you fix that?

The build is completing but the tests fail, working on sorting it out.

Putting this down for my own reference:
Okay so seems like a value can't be directly assigned to the reference returned by the value() function in optional (hence the "bad optional access" exceptions), so emplace() needs to be used instead. value_or() function only returns the value if exists or some other object, doesn't actually assign anything to the object itself.

[henningkayser]

Most of these pointers are only pointers because they are optional. If we use std::optional, we should switch members to values as long as the API is only exposing references.

[Shobuj-Paul]

Most of these pointers are only pointers because they are optional. If we use std::optional, we should switch members to values as long as the API is only exposing references.

I have changed object_types_, robot_state_ and acm_ to values.
scene_transforms_ is giving some issues, here were are trying to assign it a SceneTransforms object, but here the object has been defined as the parent class Transforms object. The pointer implementation seems to be casting it, need to see how to do the same with values.

Can't seem to be making scene_transforms_ into a value successfully, open to suggestions.

[mergify]

This pull request is in conflict. Could you fix it @Shobuj-Paul?

[Shobuj-Paul]

@sjahr
Could you review this PR?

[sjahr]

I like this change 👍 Thanks and sorry for the late response