kubespawner removes doubledash("--") from extra_containers command arguments

[dashwin82]

Bug description

I am trying to configure kubespawner.extra_containers, to add additional containers to our Jypyterlab singe user pods. If the container arguments contains "--" as inputs, then kubespawner strips and replace with "" For example, the input to kubespawner.extra_containers is as below [{'name': 'logshipper', 'imagePullPolicy': 'IfNotPresent', 'image': 'logshipper', 'args': ['stdout-redirect', '-redirect=file', '-size=2', '-rotate=5', '-logfile=/logs/logshipper.log', '--', '/opt/fluent-bit/scripts/init.sh', '--config=/etc/fluent-bit/fluent-bit.conf']

The spawned pod has the below description `- args:

• stdout-redirect
• -redirect=file
• -size=2
• -rotate=5
• -logfile=/logs/logshipper.log
• ""
• /opt/fluent-bit/scripts/init.sh
• --config=/etc/fluent-bit/fluent-bit.conf`

Expected behaviour

The expected behavior should be as below `- args:

• stdout-redirect
• -redirect=file
• -size=2
• -rotate=5
• -logfile=/logs/logshipper.log
• --
• /opt/fluent-bit/scripts/init.sh
• --config=/etc/fluent-bit/fluent-bit.conf`

Actual behaviour

Looks like kubespawner makes "--" it to null in generated pod spec

How to reproduce

As example, the jupyterhub chart install, is configured with a sample container `singleuser: extraContainers:

• name: alpine image: alpine args: ["touch", "--", "myfile",]`

  By installing the jupyterhub and logged in as user, the single-user pod, extra container shall have the following spec

alpine: Container ID: docker://13639077730bf998773f5d2c0dbc71ae035a6e15b38afa3d7ca421148be4bc99 Image: alpine Image ID: docker-pullable://alpine@sha256:7144f7bab3d4c2648d7e59409f15ec52a18006a128c733fcff20d3a4a54ba44a Port: <none> Host Port: <none> Args: touch "" myfile Looking closely, the Args have an empty line, which should have been "--"

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[minrk]

This is because of an overzealous rstrip("-"). Should be fixed by #770.