A 'task@experiment.task' override key appears in addition to 'experiment' that crash my program

[duydl]

I have a configs tree as follow:

configs
├── experiment
│   ├── default.yaml
│   └── test.yaml
├── main.yaml
└── task
    ├── 01_task.yaml
    ├── 02_task.yaml
    └── default.yaml

In main.yaml i have:

defaults:
  - _self_
  - task: default  
  - experiment: default

config_key: value
...

and in exp_test.yaml:

defaults:
  - override /task: 02_task.yaml

config_key: new_value

when running with override experiment=exp_test, i got this error

In 'experiment/exp_test': Could not override 'task@experiment.task'.
Did you mean to override task?

I found this location is where the msg originated.
https://github.com/facebookresearch/hydra/blob/0f83b0dd6127bf7acb9b31d93e62a7c10b640011/hydra/_internal/defaults_list.py#L137
Putting some debug print there, it appears that a new key is added to self.override_metadata:
{'experiment': OverrideMetadata(external_override=True, containing_config_path=None, used=True, relative_key=None), 'task@experiment.task': OverrideMetadata(external_override=False, containing_config_path='experiment/exp_test', used=False, relative_key='/task')}

I have another project that has nearly exact setup, ran in the same environment but never encountered this error.

Any idea, where the problem could be?

---

Python: 3.12.0 / 3.10.16| by Anaconda.
Hydra: 1.3.2
OS: Linux-6.8.0-48-generic-x86_64-with-glibc2.39

[duydl]

I had mispelled # @package _global_.