Dockerfile ARG default throws NPE if ARG is null

[twendelmuth]

Description

It seems like if you're building a Dockerfile with ARG and defining a default like ARG TEST=test and pass <TEST></TEST> to the plugin, this will fail with NullpointerException in https://github.com/fabric8io/docker-maven-plugin/blob/master/src/main/java/io/fabric8/maven/docker/util/DockerFileUtil.java#L268

Info

• docker-maven-plugin version : 0.39.0

• pom.xml configuration

			<plugin>
				<groupId>io.fabric8</groupId>
				<artifactId>docker-maven-plugin</artifactId>
				<version>0.39.0</version>

				<configuration>
					<images>
						<image>
							<name>example-image</name>
							<build>
								<contextDir>example</contextDir>
								<args>
									<TEST></TEST>
								</args>
							</build>
						</image>
					</images>
				</configuration>
			</plugin>

• Example Dockerfile:

FROM alpine
ARG TEST=something

The example is obviously not what is happening in the end (with that you could just ask me to remove the arg if I'm not setting it, but rather the problem that I have another variable in there which potentially is not set)

[rohanKanojia]

@twendelmuth : Hi, was this working before v0.39.0 . I'm afraid it might be due to #1524

Would it be possible for you to raise a PR to fix this?

[twendelmuth]

@rohanKanojia Sure. I don't think this was working before though. 0.38.0 & 0.38.1 both throw the same NPE, 0.37.0 just throws a more descriptive exception ;)

Execution default-cli of goal io.fabric8:docker-maven-plugin:0.37.0:build failed: null value in entry: TEST=null

[flocard02]

Hello,

Looks like the issue is still here

Execution fabric8-build of goal io.fabric8:docker-maven-plugin:0.40.2:build failed: null value in entry: TEST=null

Caused by: java.lang.NullPointerException: null value in entry: TEST=null
at com.google.common.collect.CollectPreconditions.checkEntryNotNull (CollectPreconditions.java:32)
at com.google.common.collect.ImmutableMap.entryOf (ImmutableMap.java:172)
at com.google.common.collect.ImmutableMap$Builder.put (ImmutableMap.java:282)
at com.google.common.collect.ImmutableMap$Builder.put (ImmutableMap.java:296)
at com.google.common.collect.ImmutableMap$Builder.putAll (ImmutableMap.java:324)
at com.google.common.collect.ImmutableMap$Builder.putAll (ImmutableMap.java:307)
at io.fabric8.maven.docker.service.BuildService.prepareBuildArgs (BuildService.java:210)
at io.fabric8.maven.docker.service.BuildService.buildImage (BuildService.java:171)
at io.fabric8.maven.docker.service.BuildService.buildImage (BuildService.java:71)
at io.fabric8.maven.docker.BuildMojo.proceedWithDockerBuild (BuildMojo.java:108)
at io.fabric8.maven.docker.BuildMojo.proceedWithBuildProcess (BuildMojo.java:91)
at io.fabric8.maven.docker.BuildMojo.buildAndTag (BuildMojo.java:84)

[rohanKanojia]

@flocard02 : Could you please create a new issue for this?