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InvalidDefaultArgInFrom

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InvalidDefaultArgInFrom

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Output

Using the global ARGs with default values should produce a valid build.

Description

An ARG used in an image reference should be valid when no build arguments are used. An image build should not require --build-arg to be used to produce a valid build.

Examples

❌ Bad: don't rely on an ARG being set for an image reference to be valid

ARG TAG
FROM busybox:${TAG}

✅ Good: include a default for the ARG

ARG TAG=latest
FROM busybox:${TAG}

✅ Good: ARG can be empty if the image would be valid with it empty

ARG VARIANT
FROM busybox:stable${VARIANT}

✅ Good: Use a default value if the build arg is not present

ARG TAG
FROM alpine:${TAG:-3.14}