Environment variable "NB_USER":"{username}" doesn't expand

[atanasov-ka]

I put the following environment variable to KubeSpawner but it seems that expansion is not supported over env variables.

dict(singleuser_image_spec="....",
environment={
'CHOWN_HOME': 'yes'
'NB_USER': '{username}'
},
....
)

If that isn't possible to fix maybe to add another property called for example "environment_expandable" which will allow to receive such variables?

[manics]

If you need to dynamically set environment variables you can use a pre_spawn_start hook:
https://jupyterhub.readthedocs.io/en/latest/reference/authenticators.html#using-auth-state

[consideRatio]

I know you can use "NB_USER": "$(JUPYTERHUB_USER)" to rely on k8s environment expansion instead of Kubespawners expansion, where the JUPYTERHUB_USER environment variable is set here by the Spawner base class that KubeSpawner inherits from.