Docker ARG parsing doesn't work

[twsl]

Similar to my previous issue #78, ARG parsing is still causing issues.

Using:

docker run -it --rm -v /tmp/envbuilder:/workspaces -e ENVBUILDER_GIT_URL=https://github.com/twsl/whos-there -e ENVBUILDER_INIT_SCRIPT=bash ghcr.io/coder/envbuilder

I get the following error message:

No Dockerfile specified, looking for a devcontainer.json...
Building in Devcontainer mode using /.devcontainer/devcontainer.json
error: compile devcontainer.json: user from dockerfile: parse image ref "mcr.microsoft.com/devcontainers/python:1-${VARIANT}": could not parse reference: mcr.microsoft.com/devcontainers/python:1-${VARIANT}
error: running command "envbuilder": compile devcontainer.json: user from dockerfile: parse image ref "mcr.microsoft.com/devcontainers/python:1-${VARIANT}": could not parse reference: mcr.microsoft.com/devcontainers/python:1-${VARIANT}

The ARG is specified in the devcontainer.json and has a default value in the Dockerfile.

"build": {
        "dockerfile": "Dockerfile",
        "context": "..",
        "args": {
            "VARIANT": "3.11-bookworm"
        }
    },

Am I missing something?

[twsl]

It's supposed to be fixed as already mentioned in #35, but it doesnt seem to work any longer or is caused by overwriting it in the devcontainer file?