ARG still not working properly in FROM

[ThatDockerUser]

Description

This was already discussed extensively since 2017 at #859 and partially fixed by #1299 with a new release today. I tested it, and there are several cases where it still does not work.

MWE pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>dmp-test</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <properties>
        <java.version>1.8</java.version>
        <resource.delimiter>@</resource.delimiter>
        <maven.compiler.source>${java.version}</maven.compiler.source>
        <maven.compiler.target>${java.version}</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

        <busybox.version>latest</busybox.version>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>io.fabric8</groupId>
                <artifactId>docker-maven-plugin</artifactId>
                <version>0.34.0</version>
                <configuration>
                    <images>
                        <image>
                            <alias>${project.artifactId}</alias>
                            <name>${project.artifactId}:${project.version}</name>
                            <build>
                                <contextDir>${project.basedir}</contextDir>
                                <args>
                                    <busyboxVersion>${busybox.version}</busyboxVersion>
                                    <busyboxVersionName>${busybox.version}</busyboxVersionName>
                                </args>
                            </build>
                        </image>
                    </images>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

I want to use busyboxVersion, as supplied by Maven, in my Dockerfile, so I do this:

ARG busyboxVersion
FROM busybox:${busyboxVersion}

But upon building, I get this:

[INFO] DOCKER> [dmp-test:1.0.0-SNAPSHOT] "dmp-test": Created docker-build.tar in 83 milliseconds
[ERROR] DOCKER> Unable to check image [busybox:${busyboxVersion}] : {"message":"no such image: busybox:${busyboxVersion}: invalid reference format"} (Bad Request: 400) [{"message":"no such image: busybox:${busyboxVersion}: invalid reference format"} (Bad Request: 400)]

Apparently, the ARG is not resolved, although this is the correct format as per the documentation. So, I change it to this:

ARG busyboxVersion
FROM busybox:$busyboxVersion

And get this:

[INFO] DOCKER> [dmp-test:1.0.0-SNAPSHOT] "dmp-test": Created docker-build.tar in 122 milliseconds
[ERROR] DOCKER> Unable to check image [busybox:] : {"message":"no such image: busybox:: invalid reference format"} (Bad Request: 400) [{"message":"no such image: busybox:: invalid reference format"} (Bad Request: 400)]

The ARG is now resolved, but has no content. Hence, I test this:

ARG busyboxVersion
FROM busybox:latest
ARG busyboxVersionName
LABEL busyboxVersion=${busyboxVersion}
LABEL busyboxVersionName=${busyboxVersionName}

The image is now built (since the version is again hard-coded), but upon inspecting it in Docker, I get this:

"Labels": {
    "busyboxVersion": "",
    "busyboxVersionName": "latest"
}

Once again, the ARG was resolved to an empty string, while the second ARG was interpreted correctly. I further this test like so:

FROM busybox:latest
ARG busyboxVersion
ARG busyboxVersionName
LABEL busyboxVersion=${busyboxVersion}
LABEL busyboxVersionName=${busyboxVersionName}

Now inspecting the Docker image, everything is alright:

"Labels": {
    "busyboxVersion": "latest",
    "busyboxVersionName": "latest"
}

Info

• d-m-p version : 0.34.0
• Maven version (mvn -v) :

Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
Maven home: C:\Program Files\apache-maven-3.6.3\bin\..
Java version: 11.0.7, vendor: AdoptOpenJDK, runtime: C:\Program Files\AdoptOpenJDK\jdk-11.0.7.10-hotspot
Default locale: en_US, platform encoding: Cp1252
OS name: "windows 10", version: "10.0", arch: "amd64", family: "windows"

• Docker version : 19.03.12
• If it's a bug, how to reproduce : see above
• If it's a feature request, what is your use case : -
• Sample project : see above

[ThatDockerUser]

Ping @rohanKanojia and @rhuss who extensively worked on the related issue.

[rohanKanojia]

@ThatDockerUser : Where is value of busyboxVersion picked from?

[ThatDockerUser]

@rohanKanojia From the POM, via the <args> configuration (see the MWE). busyboxVersion and busyboxVersionName have the same value, taken from the busybox.version property.

[rohanKanojia]

I wasn't aware of this <args> field in buildconfiguration. Right now plugin only considers args in Dockerfile. Let me fix it.

[ThatDockerUser]

Thanks for taking this on, I will also note here that the variable format with the braces does not work irrespective of the POM usage, such as in this:

ARG busyboxVersion=latest
FROM busybox:${busyboxVersion}

[INFO] DOCKER> [dmp-test:1.0.0-SNAPSHOT] "dmp-test": Created docker-build.tar in 160 milliseconds
[ERROR] DOCKER> Unable to check image [busybox:${busyboxVersion}] : {"message":"no such image: busybox:${busyboxVersion}: invalid reference format"} (Bad Request: 400) [{"message":"no such image: busybox:${busyboxVersion}: invalid reference format"} (Bad Request: 400)]

[rohanKanojia]

I'm checking this case when you build with a Dockerfile like this:

ARG busyboxVersion
FROM busybox:latest
ARG busyboxVersionName
LABEL busyboxVersion=${busyboxVersion}
LABEL busyboxVersionName=${busyboxVersionName}

Even when I build this with plain docker, it doesn't seem to be resolved. I think it's more of a docker behavior rather than plugin's, maybe arg was no longer in build scope after passing from:

docker build --build-arg busyboxVersion=latest --build-arg busyboxVersionName=latest -t busybox_ltest:latest .

...

docker : $ docker inspect 9d951b5ac865 | grep -A3 "Labels"
            "Labels": {
                "busyboxVersion": "",
                "busyboxVersionName": "latest"
            }
--
            "Labels": {
                "busyboxVersion": "",
                "busyboxVersionName": "latest"
            }
docker : $ 

[ThatDockerUser]

Maybe that is also a bug within Docker, but any ARG configured prior to the FROM remains valid in the FROM. The PR addresses this, so I hope it can be merged and released soon.