Resource env var, with transport interface

[chapulina]

• Resolves Insert models from local paths #123.
• Requires More file path APIs gz-common#70
• Builds on top of Move test Relay to its own file #181

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This allows models and meshes to be found according to the the IGN_GAZEBO_RESOURCE_PATH environment variable.

• It's the Ignition Gazebo equivalent of both GAZEBO_MODEL_PATH and GAZEBO_RESOURCE_PATH.
• That variable is already being used to find worlds, now it's extended to <include>s and mesh <uri>s.
• The name "resources" is better fitting than "model", since it can load different types of resources.
• We've already been supporting the SDF_PATH and IGN_FILE_PATH variables with the same behaviour, so this implementation is backwards compatible and keeps those variables in sync with IGN_GAZEBO_RESOURCE_PATH.
• I added a transport interface so these paths can be queried and updated.
  • The first consumer will be the new GUI resources plugin, see Insert model from the GUI #31
  • This keeps the ground truth in the server. Gazebo-classic users often would have issues because gzserver and gzclient would be in different shells and have access to different environment variables. See this outstanding issue: Update model paths on both gzclient and gzserver at runtime gazebo-classic#2403
  • I kept the services in the global namespace because worlds can be found through the paths, so the paths are at a level above worlds.

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Try it

Get paths:

ign service -s /gazebo/get_resource_paths --reqtype ignition.msgs.Empty --reptype ignition.msgs.StringMsg_V --timeout 5000 --req "unused: false"

Add path:

ign service -s /gazebo/add_resource_paths --reqtype ignition.msgs.StringMsg_V --reptype ignition.msgs.Empty --timeout 5000 --req "data: '/tmp/lala'"

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TODOs

I'll leave this in draft state until:

• Updates to this tutorial are added to this PR: https://github.com/ignitionrobotics/ign-gazebo/blob/master/tutorials/resources.md
• This design document is updated to reflect this PR: https://github.com/ignitionrobotics/design/pull/1/files I opened a new design PR instead: Guidelines for finding resources design#4

[maryaB-osr]

lgtm!

[codecov]

Codecov Report

Merging #172 into ign-gazebo2 will increase coverage by 8.92%.
The diff coverage is 72.72%.

@@               Coverage Diff               @@
##           ign-gazebo2     #172      +/-   ##
===============================================
+ Coverage        53.78%   62.70%   +8.92%     
===============================================
  Files              121      124       +3     
  Lines             5838     6200     +362     
===============================================
+ Hits              3140     3888     +748     
+ Misses            2698     2312     -386     

Impacted Files	Coverage Δ
include/ignition/gazebo/Server.hh	100.00% <ø> (ø)
src/gui/Gui.cc	5.93% <0.00%> (+5.93%)	⬆️
src/gui/PathManager.cc	0.00% <0.00%> (ø)
src/systems/physics/Physics.cc	15.98% <ø> (ø)
src/systems/scene_broadcaster/SceneBroadcaster.cc	36.24% <0.00%> (-0.12%)	⬇️
src/systems/user_commands/UserCommands.hh	100.00% <ø> (ø)
src/systems/user_commands/UserCommands.cc	12.29% <16.66%> (ø)
src/Util.cc	84.74% <97.82%> (+8.35%)	⬆️
src/LevelManager.cc	90.71% <100.00%> (+49.10%)	⬆️
src/SdfGenerator.cc	95.61% <100.00%> (+0.07%)	⬆️
... and 27 more

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[chapulina]

@osrf-jenkins run tests please

[chapulina]

@JShep1, I think this is ready to be used by #173 . Let me know if you run into any problems.

[JShep1]

I just ran this and am running into an issue with ign gazebo only showing a black screen with the message

[GUI] [Dbg] [Gui.cc:144] GUI requesting list of world names. The server may be busy downloading resources. Please be patient.

being printed every few seconds. I replicated this issue on my laptop as well, are you running into this? @chapulina

I believe the changes that broke things are in this diff 00d9235 - those are the changes I merged into the insert local models branch that made it give this error.

[chapulina]

@JShep1 , a086574 has a temporary fix to that issue. For some reason the global node works when doing ign gazebo -s and ign gazebo -g separately, but not for ign gazebo 🤔 I'll look better into it tomorrow. For now, be warned that if you add any paths through the add service, the GUI will not know about them automatically, which may cause some models to fail.

[chapulina]

Ok, this should be good to be reviewed again. @JShep1 , let me know if you need help using it on #173 .

[chapulina]

The 3 test failures are not there on ign-gazebo2, I'll take a look: https://build.osrfoundation.org/job/ignition_gazebo-ci-pr_any-ubuntu_auto-amd64/3765/testReport/

[chapulina]

The 3 test failures are not there on ign-gazebo2

Not true, they're there on ign-gazebo2 now.