Legacy ENV key value with a multi-word value becomes an invalid key=value #69

Converting a legacy ENV key value instruction to the key=value form breaks when the value contains spaces. The output is not a valid Dockerfile: docker build rejects it, and so does dockerfmt on the next run.

Reproduce

FROM alpine
ENV JAVA_OPTS -Xms256m -Xmx512m

dockerfmt Dockerfile

Actual

FROM alpine
ENV JAVA_OPTS=-Xms256m -Xmx512m

The original builds and sets JAVA_OPTS=-Xms256m -Xmx512m. docker build on the output, and dockerfmt run on it again, both fail with:

Error parsing file: Syntax error - can't find = in "-Xmx512m". Must be of the form: name=value

Expected

In the legacy form everything after the key is the value, so the converted instruction needs quotes:

ENV JAVA_OPTS="-Xms256m -Xmx512m"

Leaving the instruction in its legacy form would also be correct.

Impact

With --write the Dockerfile no longer builds. In a sample of about 450 real-world Dockerfiles, 112 lines used the legacy ENV form and one of them had an unquoted multi-word value.

Reproduced with v0.5.4 and with main at a5868c2.