Support LegacyKeyValueFormat warning

[akurtakov]

From docker build I get:

1 warning found:
 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 21)
Legacy key/value format with whitespace separator should not be used
More info: https://docs.docker.com/go/dockerfile/rule/legacy-key-value-format/
Dockerfile:21
--------------------
  19 |     
  20 |     ENV HOME=/home/vnc
  21 | >>> ENV DISPLAY :0
  22 |     
  23 |     RUN mkdir -p ${HOME}/.vnc && chmod -R 775 ${HOME} \
--------------------

It would be nice if the language server creates a diagnostic warning for the issue and ideal if there is a codeaction to change it to the non-legacy format.

[rcjsuen]

@akurtakov Have you tried using the Docker Language Server? That one will report the errors that docker build reports. It does not provide a code action though and I've opened docker/docker-language-server#411 over there to track it.

[akurtakov]

But that one would not show the diagnostic until docker build is run, right?

[akurtakov]

Also shipping this one with linuxtools is simpler as I can simply npm install during build and ship result on all platforms. I can't do that with the Go based plugins as I would have to come with fragments and etc, right?

[rcjsuen]

But that one would not show the diagnostic until docker build is run, right?

The scans are being performed in the background. You can see that it has been triggered even though I have not yet saved the file.

2025-08-07-real-time-biuld-warnings.mov

Also shipping this one with linuxtools is simpler as I can simply npm install during build and ship result on all platforms. I can't do that with the Go based plugins as I would have to come with fragments and etc, right?

You are correct that the other one being in Go comes with its own trade-offs when compared to this one that is written in TypeScript.