Make it possible to run scalafix with the same scala binary version as the target

[bjaglin]

This is necessary for advanced rules using the presentation compiler such as ExplicitResultTypes to work.

See

• cross-build Scalafix for 2.13 scalacenter/scalafix#1111
• https://github.com/scalacenter/scalafix/pull/1152/files#diff-8f1370021f0c21599d22a292e6ee5a9446f05c18a05f5c3bb250dea3884c72eeR86
• allow usage of rules compiled against 2.11 & 2.13 scalacenter/sbt-scalafix#121

[marcelocenerine]

@bjaglin the Gradle plugin used to use the scalafix-interfaces jar and dynamically load Scalafix via a custom classloader. But for some reason I scratched that and started using the scalafix-cli jar instead: https://github.com/cosmicsilence/gradle-scalafix/pull/18/files#diff-49a96e7eea8a94af862798a45174e6ac43eb4f8b4bd40759b5da63ba31ec3ef7L19 . IIRC we were running into OOM issues in our integration tests due to scalafix + scala and all transitive dependencies being loaded multiple times via different classloader instances (on the same JVM). I will try to revisit that during my time off in the upcoming weeks.

Thanks for the pointers 👍 . It looks like Scalafix.fetchAndClassloadInstance simplifies things a lot.

[bjaglin]

Thanks for working on that! I see you kept classloading on the plugin side - no luck with caching Scalafix.fetchAndClassloadInstance?

[marcelocenerine]

@bjaglin I did consider using fetchAndClassloadInstance (and it worked), but ultimately I decided to stick to Gradle's own dependency resolution mechanism for now (which is the approach I had before). I will revisit that once I get time to do more testing though.