Do not ever exclude junit if Testcontainers is used

[DidierLoiseau]

What's changed?

Instead of adding the JUnit 4 exclusion to all dependencies and then removing it from specific ones that depend on Testcontainers, just don’t add the exclusion when Testcontainers is used.

What's your motivation?

We have implemented some test libraries that (transitively) depend on Testcontainers. When (indirectly) running the JUnit 5 migration recipe, it always adds the junit exclusion on those, which breaks the build. This forces us to un-exclude JUnit 4 as a followup recipe.

Have you considered any alternatives or workarounds?

Current workaround is to remove the exclusion explicitly for all dependencies after JUnit 5 migration:

  - org.openrewrite.maven.RemoveExclusion:
      groupId: '*'
      artifactId: '*'
      exclusionGroupId: junit
      exclusionArtifactId: junit

Any additional context

This makes the recipe more conservative. If a project transitively depends on Testcontainers, it won’t add the exclusion to dependencies that do not depend on Testcontainers (but still depend on JUnit 4) but that’s ok since exclusions have to be added everywhere to work properly.

This provides a more generic solution to #429 and #477.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[DidierLoiseau]

I actually wanted to provide a pom with the junit dependency in the test, and then run it as:

        rewriteRun(
          mavenProject("depends-on-junit", pomXml(remoteDepWithJunit, SourceSpec::skip)),
          mavenProject("needs-exclusion", pomXml(before, after)));

and somehow it works – the exclusion is added as intended – but it also gets a MavenDownloadException added in the output.

I was trying to do the same as other Maven tests that use SourceSpec::skip, but they all seem to do that for a parent, not a dependency.

[timtebeek]

Welcome back! Great use of a precondition indeed for this longer standing wart in our recipes.

Still will keep fingers crossed for a Junit4-less-version-of-testcontainers

• testcontainers/testcontainers-java#970
• testcontainers/testcontainers-java#10351