fix(docker): prepend ARG BASE to overlay Dockerfiles#182
Merged
Conversation
Docker requires ARG declared in global scope (before first FROM) for build-arg substitution to work in FROM instructions. User Dockerfiles that omit ARG BASE fail with 'base name should not be blank'. Prepending ARG BASE is a no-op when already declared — duplicate bare ARGs are harmless and --build-arg always overrides any default.
Contributor
There was a problem hiding this comment.
Pull request overview
This PR addresses Docker overlay builds failing when an overlay Dockerfile uses FROM ${BASE} without declaring ARG BASE before the first FROM, by automatically injecting a global ARG BASE into the loaded overlay Dockerfile content.
Changes:
- Prepend
ARG BASEto overlay Dockerfile content inBuildOverlayImageto enable${BASE}substitution inFROM. - Add an integration test covering overlay builds where the Dockerfile omits an explicit
ARG BASE.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
internal/docker/docker.go |
Prepends ARG BASE to loaded overlay Dockerfiles prior to building. |
internal/docker/docker_integration_test.go |
Adds an integration test ensuring overlays without ARG BASE don’t fail with “base name (${BASE}) should not be blank”. |
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
Prepending ARG BASE at byte 0 breaks Dockerfiles starting with parser directives (# syntax=..., # escape=..., # check=...) which must appear before any instruction. Now scans past leading directives and blank lines before injecting.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Overlay Dockerfiles that use
FROM ${BASE}without declaringARG BASEin global scope fail with:Docker requires the ARG declared before the first FROM for substitution to work. This prepends
ARG BASE\nto every loaded overlay Dockerfile — harmless when already declared (duplicate bare ARGs are no-ops), and--build-argalways overrides any default.