Containerfile parameter expansion syntax not parsed correctly

[sanmai-NL]

• This is a bug report
• This is a feature request
• I searched existing issues before opening this one

A feature of Dockerfile syntax (1.6.0) is shell parameter expansion. In Docker Engine, Podman and nerdctl, these can be used to, e.g., fail a build when a build arg is unset ({VAR?} or when empty or unset {VAR:?}). I haven't found documentation for the feature by Docker Inc.

Expected behavior

Shell parameter expansions are parsed. For Hadolint, I presume this requires at minimum expanding the grammar/parser, without doing anything with the semantics.

Actual behavior

Shell parameter expansions not parsed, resulting in fatal failure.

Steps to reproduce the behavior

$ hadolint Containerfile

Containerfile:5:31 unexpected ':' expecting '@', '\', a new line followed by the next instruction, or the image tag

Output of hadolint --version or
docker run --rm hadolint/hadolint hadolint --version or
docker run --rm ghcr.io/hadolint/hadolint hadolint --version:

Haskell Dockerfile Linter 2.12.0

Dockerfile (if relevant)

# syntax=docker.io/docker/dockerfile:1@sha256:ac85f380a63b13dfcefa89046420e1781752bab202122f8f50032edf31be0021
ARG IMAGE_PREFIX=
ARG DISTRO=alpine
ARG VERSION_DISTRO=3.19
FROM ${IMAGE_PREFIX:?}${DISTRO:?}:${VERSION_DISTRO:?}

Additional environment details (OS, stack version, etc.)