Autofix directory structure based on package in scala - scala

Question

I have a file src/main/scala/foo.scala which needs to be inside package bar. Ideally the file should be inside src/main/scala/bar/foo.scala.
// src/main/scala/foo.scala
package bar
// ...
How can I auto-fix this issue throughout my project such that the folder structure matches the package structure?
Is there any SBT plugin etc that can help me fix this issue?

Answer 1

As far as I am aware there are not such tools, though AFAIR IntelliJ can warn about package-directory mismatch.
Best I can think if is custom scalafix (https://scalacenter.github.io/scalafix/) rule - scalafix/scalameta would be used to check file's actual package, translate it to an expected directory and if they differ, move file.
I suggest scalafix/scalameta because there are corner cases like:
you are allowed to write your packages like:
package a
package b
package c
and it almost like package a.b.c except that it automatically imports everything from a and b
you can have package object in your file and then if you have
package a.b
package object c
this file should be in a/b/c directory
so I would prefer to check if file didn't fall under any of those using some existing tooling.
If you are certain that you don't have such cases (I wouldn't without checking) you could:
match the first line with regexp (^package (.*))
translate a.b.c into a/b/c (matched.split('.').map(_.trim).mkString(File.separator))
compare generated location to an actual location ( I suggest resolving absolute file locations)
move file if necessary
If there is a possibility of having more complex case than that, I could replace first step by querying scalafix/scalameta utilities.

Answer 2

Here is an sbt plugin providing packageStructureToDirectoryStructure task that reads package statements from source files, creates corresponding directories, and then moves files to them
import sbt._
import sbt.Keys._
import better.files._
object PackagesToDirectories extends AutoPlugin {
object autoImport {
val packageStructureToDirectoryStructure = taskKey[Unit]("Make directory structure match package structure")
}
import autoImport._
override def trigger = allRequirements
override lazy val projectSettings = Seq(
packageStructureToDirectoryStructure := {
val log = streams.value.log
log.info(s"Refactoring directory structure to match package structure...")
val sourceFiles = (Compile / sources).value
val sourceBase = (Compile / scalaSource).value
def packageStructure(lines: Traversable[String]): String = {
val packageObjectRegex = """package object\s(.+)\s\{""".r
val packageNestingRegex = """package\s(.+)\s\{""".r
val packageRegex = """package\s(.+)""".r
lines
.collect {
case packageObjectRegex(name) => name
case packageNestingRegex(name) => name
case packageRegex(name) => name
}
.flatMap(_.split('.'))
.mkString("/")
}
sourceFiles.foreach { sourceFile =>
val packagePath = packageStructure(sourceFile.toScala.lines)
val destination = file"$sourceBase/$packagePath"
destination.createDirectoryIfNotExists(createParents = true)
val result = sourceFile.toScala.moveToDirectory(destination)
log.info(s"$sourceFile moved to $result")
}
}
)
}
WARNING: Make sure to backup the project before running it.