Syntax directive failing behind corporate docker mirror (e.g. artifactory)

[danjamesmay]

I have the following error, running the devcontainer cli on @devcontainers/cli 0.56.0. Node.js v20.11.0. linux 5.15.133.1-microsoft-standard-WSL2 x64., which appears to stem from here:

cli/src/spec-node/containerFeatures.ts

Line 248 in bdc49a5

useBuildKitBuildContexts && !(imageBuildInfo.dockerfile && supportsBuildContexts(imageBuildInfo.dockerfile)) ? '# syntax=docker/dockerfile:1.4' :

 => ERROR resolve image config for docker.io/docker/dockerfile:1.4                                                              0.1s
------
 > resolve image config for docker.io/docker/dockerfile:1.4:
------
Dockerfile-with-features:1
--------------------
   1 | >>> # syntax=docker/dockerfile:1.4
   2 |     ARG _DEV_CONTAINERS_BASE_IMAGE=placeholder
   3 |     FROM <my_corp_mirror>/library/golang:1.20-bullseye AS dev_container_auto_added_stage_label
--------------------
ERROR: failed to solve: failed to authorize: failed to fetch anonymous token: Get "https://auth.docker.io/token?scope=repository%3Adocker%2Fdockerfile%3Apull&service=registry.docker.io": Forbidden

I worked around this by adding the --buildkit never option to the build command, but this isn't ideal for futureproofing.

I can see there appears to be a new flag for a related issue here: #728, which adds a hidden --omit-syntax-directive flag. When will this be released?

I believe anyone who works with the devcontainer cli behind a corporate docker mirror like artifactory will be blocked by this issue until the workaround is provided. It appears the syntax comment goes off to the public docker.io site to get whatever the directive provides and as this is not configurable. I can go off to get this image with docker pull <corp_mirror>/docker/dockerfile:1.4.0, but obvs the syntax directive isn't configurable so I can't make this work.