More complex builds for github:org/repo rewrites

[olafurpg]

Currently, github:org/repo rewrites need to fit in a single file. It would be nice if scalafix supported more complex builds to accommodate

• multiple files
• dependencies
• custom scalac options?
• generated sources (e.g., BuildInfo)

There are several ways to achieve this

• add scalafix/build.conf file that includes the build definition (files, dependencies, options). This would mean pretty much re-implementing a build tool.
• invoke sbt programmatically to builds the scalafix/rewrites projects from source. sbt rewrites/fullClasspath will give the classpath and scalafix won't have to compile sources itself.

I'm personally leaning towards the second option. I don't have much experience with using sbt programmatically or with sbt source dependencies but if it works then it's a very powerful solution. Also, this solution would give incremental and cached compilation.

[gabro]

Yeah, let's not implement our own build tool 👍

[olafurpg]

After more thinking, here is what I think strikes a nice balance between supporting more complex builds without reinventing the wheel

• github:org/repo clones org/repo with jgit
• compiles all .scala sources in the scalafix/rules directory (and scalafix/rewrites for compat with <0.5 directories)
• classload all rules in compiled sources, if there is a /v1 suffix, classload all rules in package rule.v1 package

This scheme scales nicely for both migration rewrites with a /v1 suffix and non-migration rules such as olafurpg/FinalCaseClass, which don't have a /v1 suffix.

This allows rules like typelevel/cats/v1 to become more complex without requiring a publish step to maven.

This approach will also scale nicely for non-GitHub projects, since it's based on git.

[gabro]

github:org/repo clones org/repo with jgit

👍 I would clone it with --depth=1

[olafurpg]

I suggest that we close this ticket with "Please publish your rule to maven central". Published rules have the same UX as built-in scalafix rules. Rules that want to enjoy the benefits of being compileable from source will need to meet the criteria

• no dependencies
• single file