Ignore empty List<String> configuration values

[chonton]

Allow empty list elements. This often occurs when a parent (corporate) pom has configuration values that are overridden by some, but not all, children.

[codecov]

Codecov Report

Merging #816 into master will increase coverage by 0.06%.
The diff coverage is 92.85%.

@@             Coverage Diff             @@
##             master    #816      +/-   ##
===========================================
+ Coverage     47.53%   47.6%   +0.06%     
  Complexity     1072    1072              
===========================================
  Files           134     134              
  Lines          6927    6936       +9     
  Branches        911     913       +2     
===========================================
+ Hits           3293    3302       +9     
  Misses         3350    3350              
  Partials        284     284

Impacted Files	Coverage Δ	Complexity Δ
...ic8/maven/docker/config/RunImageConfiguration.java	86.86% <100%> (+0.72%)	36 <1> (ø)	⬇️
...ain/java/io/fabric8/maven/docker/util/EnvUtil.java	65.27% <100%> (+3.05%)	41 <2> (+3)	⬆️
...8/maven/docker/config/BuildImageConfiguration.java	82.71% <75%> (ø)	45 <3> (-1)	⬇️
...bric8/maven/docker/assembly/DockerFileBuilder.java	90.1% <0%> (-1.05%)	72% <0%> (-2%)

[rhuss]

Thanks for the PR ! I wonder though whether there is a valid scenario where a null element is valid entry and should not be squeezed out ? Ad-hoc I can't think about one, but if such a use case exists, it would be problematic here.

[rhuss]

minor nitpick: Could we rename it to removeNullEntries() ?

[chonton]

A command line equivalent would be docker run -p "" image. This results in the message docker: No port specified: <empty>.

I want to make sure we agree on the distinction between null and empty. When I say null entry, I mean list.get(x) == null; when I say empty entry, I mean list.get(x).isEmpty() == true.

I'm not sure that maven injection can create a null entry. I've definitely seen empty entries; the following produces an empty entry:

<ports>
  <port></port>
</ports>

I'm fine with renaming method. Does removeNullEntries entirely describe the removal of both null and empty values?

As I write this, I wonder if the strings should also have trim() applied?

[rhuss]

Ah. ok. I thought it was about null entries. We should keep it of course like this, maybe calling it 'removeEmptyEntries()' ?

Trim is find for me, too.

[rhuss]

Thanks a lot ! One last plea: Could you please update the doc/changelog.md referencing this fix ?

[chonton-elementum]

@rhuss, did you intend to merge this into master or not? Do I need to create another pull request with new base?

[rhuss]

Sorry, I simply forgot to merge ;-)

[merge]