`getFirstFinalizedProtoInstance()` returns `NULL` for DEF with Lua code in v2023b about webots

[omichel]

Unfortunately, I have no idea on how to fix this. I would recommend the following to investigate:

1. Check if the problem is the same with a Javascript proto (instead of Lua).
2. Check the change log of R2023b to identify which PR may have caused this bug.

[galou]

Candidates: #5978, #5676, #5774.

[galou]

A PROTO with Javascript rather than Lua suffers from the same symptoms.

[galou]

Can I debug the generated PROTO files (after going through the engine)?

[omichel]

Yes, there is a menu in the scene tree allowing to see the generated proto file.

[galou]

When trying to write a small example to reproduce the issue, I wrote this PROTO:

#VRML_SIM R2023b utf8
#     Robot {
#       children [
#         DEF led LED {
#         }
#       ]
#       controller "my_supervisor"
#       supervisor TRUE
#     }
# 


PROTO MyRobot [
  field SFVec3f translation 0 0 0
  field SFRotation rotation 0 0 1 0
  field SFString name "robot"
]
{
  Robot {
    translation IS translation
    rotation IS rotation
    name IS name
    controller "my_supervisor"
    supervisor TRUE
    children [
        DEF %{= "led" }% LED {
        }
    ]
  }
}

with this supervisor:

"""my_supervisor controller."""

# You may need to import some classes of the controller module. Ex:
#  from controller import Robot, Motor, DistanceSensor
from controller import Supervisor

class Test(Supervisor):

    def __init__(self):
        super().__init__()

    def run(self):
        my_led = self.getFromDef('my_led')
        led = my_led.getFromProtoDef('led')
        print(f'{led=}')
        print(f'{led.getPosition()=}')

controller = Test()
controller.run()

and this world

#VRML_SIM R2023b utf8

EXTERNPROTO "https://raw.githubusercontent.com/cyberbotics/webots/26e08bbf6049f8d3ec3af3dd874e5f5d4062ab96/projects/objects/backgrounds/protos/TexturedBackground.proto"
EXTERNPROTO "https://raw.githubusercontent.com/cyberbotics/webots/26e08bbf6049f8d3ec3af3dd874e5f5d4062ab96/projects/objects/backgrounds/protos/TexturedBackgroundLight.proto"
EXTERNPROTO "../protos/MyRobot.proto"

WorldInfo {
}
Viewpoint {
  orientation -0.5773502691896257 0.5773502691896257 0.5773502691896257 2.0944
  position 0 0 10
}
TexturedBackground {
}
TexturedBackgroundLight {
}
DEF transform Pose {
  children [
    DEF my_led MyRobot {
    }
  ]
}

but this combination does NOT trigger the issue. I'll have to dig farther.

[galou]

I'm trying to understand the code. What is a PROTO parameter node? In our case, when the issue appears, protoParameterNodeInstances() returns an empty list.

[omichel]

I am not sure, but it could be the nodes that are passed as PROTO parameters.

[galou]

Do you mean a parameter whose type is a node?

[omichel]

Yes.

[galou]

git bisect allowed to determine that the bug was introduced in b95a736 "Refactor node and PROTO creation (#5779)"

[omichel]

Nice catch! I would suggest you to investigate commit-per-commit on #5779 to understand which commit did introduce the bug. Unfortunately @stefaniapedrazzi is not working any more with us and won't be able to help you on this.