dev_container: Expand bare $VAR in addition to ${VAR} in Dockerfiles#59280
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tnayuki wants to merge 2 commits into
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dev_container: Expand bare $VAR in addition to ${VAR} in Dockerfiles#59280tnayuki wants to merge 2 commits into
tnayuki wants to merge 2 commits into
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Dockerfiles commonly use the bare form \$VAR alongside the braced \${VAR}
form (e.g. `FROM ruby:\$RUBY_VERSION`). The expansion loop only handled
the braced form, so bare references were passed through verbatim, causing
`docker inspect` to fail with the literal string instead of the resolved
value.
Add `expand_dockerfile_var` which handles both forms. Bare \$KEY is
replaced only when not immediately followed by a word character, so
\$RUBY_VERSION2 is not consumed when expanding \$RUBY_VERSION.
Signed-off-by: Toru Nayuki <tnayuki@icloud.com>
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When expanding build args in a dev container Dockerfile, only the braced
${VAR}form was substituted. The bare$VARform — which is valid Dockersyntax and common in real-world Dockerfiles — was passed through verbatim.
For example, the Rails dev container images use:
This left
$RUBY_VERSIONunexpanded, so the subsequentdocker inspect/build ran against the literal string
ruby:$RUBY_VERSIONand failed withan invalid reference format.
This adds
expand_dockerfile_var, which substitutes both${VAR}and bare$VAR. Bare$KEYis only replaced when it is not immediately followed bya word character, so expanding
$RUBY_VERSIONdoes not partially consume$RUBY_VERSION2.Self-Review Checklist:
Release Notes:
$VARform