Failed to load some model from resourse spawner in gz-harmonic

[Safin-Sadman]

Environment

• Ubuntu 24.04
• Gazebo Sim 8.11.0 (Harmonic)

Steps to reproduce

1. Launch an empty world:

   gz sim empty.sdf

2. Open the Resource Spawner plugin.

3. Search for the official Open Robotics Spectrum Plane model.

4. Download the model.

5. Click Spawn.

Expected behavior

The model is inserted into the world.

Actual behavior

The model is not spawned. The console reports:

Error [Utils.cc:176] Tried to use callback in sdf::findFile(), but the callback is empty.
Did you call sdf::setFindCallback()?

Additional observations

I tested several official Fuel models using the same workflow:

• ✅ Breakfast Menu Original
• ✅ Construction Barrel
• ✅ Coke Can
• ✅ Office Chair
• ✅ Pioneer3AT (spawns, but reports a missing libSkidSteerDrivePlugin.so)
• ❌ Spectrum Plane (does not spawn)

This appears to be specific to the Spectrum Plane model or its interaction with the Resource Spawner, rather than a general Resource Spawner failure.

[Pengkun-ZHU]

The cause appears to be that Spectrum Plane is a little special in how its path hierarchy is organized for Resource Spawner.
Most Fuel models download to a directory with a standard model.sdf, but Spectrum Plane’s model.config points to spectrum_plane.sdf. The Resource Spawner code ignored that and hardcoded as below:
common::joinPaths(localPath, "model.sdf")

I can try to work on a fix this weekend. Would it be possible to assign this issue to me? Also, please let me know if someone is already taking over.