Instructions with only the escape character should be flagged as an error

[rcjsuen]

FROM scratch
USER \

$ docker build .
Sending build context to Docker daemon  46.79MB
Error response from daemon: Dockerfile parse error line 2: USER requires exactly one argument

The validation code does not consider USER \ as an error but it should.

let dockerfileUtils = require("dockerfile-utils");
let diagnostics = dockerfileUtils.validate("FROM scratch\nUSER \\");
console.log(diagnostics.length);

0