Spotless for imports

[MartinWitt]

Currently, our import ordering in spoon is a bit messy. This leads to an unpleasant time with IntelliJ trying to sort the imports in a more normal order. Why don't we use spotless-maven-plugin to sort all our imports in a fixed sorting? This also helps to reduce diffs in the future for PRs. The benefit compared to checkstyle is that we can do the sorting automatic. See https://github.com/diffplug/spotless/tree/main/plugin-maven#java for an example.

[MartinWitt]

We need to add

          <java>
            <importOrder />
          </java>

Any wishes for the order?
<order>java|javax,org,com,com.diffplug,,\#com.diffplug,\#</order>
<semanticSort>false</semanticSort>
<wildcardsLast>false</wildcardsLast>

[I-Al-Istannen]

I don't care as long as IJ can follow the same order and I don't need to run spotless :^)

[algomaster99]

Can we please add a good-first-issue label here? We can then ask new contributors to work on this :)

[monperrus]

done

[micka-lama]

Hello, I would like to try to contribute on this issue.

I noticed that Spotless is applied to the files included in src/test/java/spoon/testing/assertions/**/*.java. I plan to accept all the Java files excepted the resources (example: **/resources/**). But, there will be a lot of changes due to the initial Plantir format usage on src/test/java/spoon/testing/assertions/**/*.java (around 1550 Java files impacted). May I remove this particular format?

I suggest also to add <removeUnusedImports />. There are 29 files impacted.
By using only <importOrder />, there are 735 files impacted.

I guess it is better to do a PR only about the pom.xml change and another one about the spotless:apply.

[algomaster99]

Hi @micka-lama ! We would want to be similar to IJ style guide. @I-Al-Istannen do you use the formatted in IJ with default configurations? We could then configure spotless accordingly.

[I-Al-Istannen]

Yea, just the defaults (except forbidding star imports). static imports are split and placed after the normal imports:

non-static
<blank>
static javax
static java
<blank>
static *

[algomaster99]

@micka-lama we look forward to your PR that configures spotless following two rules:

1. Sticking to IJ style guide.
2. Configure the style guide for imports like @I-Al-Istannen said. You can also include configuration for IntelliJ workspace so that they don't contradict with spotless.