Escaped whitespace variable values in ENV instructions are incorrect

[rcjsuen]

FROM scratch
ENV var=\  var2=\

Given the above Dockerfile, hovering over var should give as its value. However, an empty string is returned instead.

$ docker build .
Sending build context to Docker daemon  86.15MB
Step 1/2 : FROM scratch
 --->
Step 2/2 : ENV var \  var2
 ---> Running in 4c2cbfe43c37
 ---> 6f1edc381410
Removing intermediate container 4c2cbfe43c37
Successfully built 6f1edc381410
$ docker inspect 6f1ed
[
    {
        "Id": "sha256:6f1edc3814101cbefed44b9d0cd358bcb5f794517bd964223102e6b1d4cafc02",
        "RepoTags": [],
        "RepoDigests": [],
        "Parent": "",
        "Comment": "",
        "Created": "2017-08-01T02:53:45.530476498Z",
        "Container": "4c2cbfe43c37b37a2bfb0b2eae2cea070a6af73d510e4f158e4c187d3051df24",
        "ContainerConfig": {
            "Hostname": "4c2cbfe43c37",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "var= ",
                "var2="
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "#(nop) ",
                "ENV var=  var2="
            ],
            "Image": "",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": null
        },
        "DockerVersion": "17.06.1-ce-rc1",
        "Author": "",
        "Config": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "var= ",
                "var2="
            ],
            "Cmd": null,
            "Image": "",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": null
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 0,
        "VirtualSize": 0,
        "GraphDriver": {
            "Data": null,
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers"
        }
    }
]