Scalafmt support (#308)

* add scalafmt module, that formats all sources files on every run

* scalafmt worker that internally chaches reformatted files

* move jvm process call to helper method

* use scala 2.12.4 to resolve scalafmt deps; check for config file existence; add quiet flags to scalafmt CLI

* make a scalafmt worker a singleton

* add tests for scalafmt module

* add reformatAll command

* tests for reformatAll command

* add docs about scalafmt support

4 files changed, 125 insertions, 0 deletions

diff --git a/scalalib/test/resources/scalafmt/core/resources/application.conf b/scalalib/test/resources/scalafmt/core/resources/application.conf
new file mode 100644
index 00000000..f5f89257
--- /dev/null
+++ b/scalalib/test/resources/scalafmt/core/resources/application.conf
@@ -0,0 +1 @@
+foo.bar = 2
diff --git a/scalalib/test/resources/scalafmt/core/src/Main.scala b/scalalib/test/resources/scalafmt/core/src/Main.scala
new file mode 100644
index 00000000..a5c74235
--- /dev/null
+++ b/scalalib/test/resources/scalafmt/core/src/Main.scala
@@ -0,0 +1,7 @@
+
+object Main extends App{
+  val person = Person.fromString("rockjam:25")
+  val greeting = s"hello ${person.name}, your age is: ${person.age}"
+  println(greeting)
+}
+
diff --git a/scalalib/test/resources/scalafmt/core/src/Person.scala b/scalalib/test/resources/scalafmt/core/src/Person.scala
new file mode 100644
index 00000000..b296cf85
--- /dev/null
+++ b/scalalib/test/resources/scalafmt/core/src/Person.scala
@@ -0,0 +1,12 @@
+object Person {
+  def fromString(s: String): Person = {
+    val Array(name, age) = s.split(":")
+    Person(
+      name,
+      age.toInt)
+  }
+}
+
+
+
+case class Person(name: String, age: Int)
diff --git a/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala b/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
new file mode 100644
index 00000000..fcff52a3
--- /dev/null
+++ b/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
@@ -0,0 +1,105 @@
+package mill.scalalib.scalafmt
+
+import ammonite.ops._
+import mill.main.Tasks
+import mill.scalalib.ScalaModule
+import mill.util.{TestEvaluator, TestUtil}
+import utest._
+import utest.framework.TestPath
+
+object ScalafmtTests extends TestSuite {
+
+  trait TestBase extends TestUtil.BaseModule {
+    def millSourcePath =
+      TestUtil.getSrcPathBase() / millOuterCtx.enclosing.split('.')
+  }
+
+  object ScalafmtTestModule extends TestBase {
+    object core extends ScalaModule with ScalafmtModule {
+      def scalaVersion = "2.12.4"
+    }
+  }
+
+  val resourcePath = pwd / 'scalalib / 'test / 'resources / 'scalafmt
+
+  def workspaceTest[T, M <: TestUtil.BaseModule](
+      m: M,
+      resourcePath: Path = resourcePath)(t: TestEvaluator[M] => T)(
+      implicit tp: TestPath): T = {
+    val eval = new TestEvaluator(m)
+    rm(m.millSourcePath)
+    rm(eval.outPath)
+    mkdir(m.millSourcePath / up)
+    cp(resourcePath, m.millSourcePath)
+    t(eval)
+  }
+
+  def tests: Tests = Tests {
+    'scalafmt - {
+      def checkReformat(reformatCommand: mill.define.Command[Unit]) =
+        workspaceTest(ScalafmtTestModule) { eval =>
+          val before = getProjectFiles(ScalafmtTestModule.core, eval)
+
+          // first reformat
+          val Right(_) = eval.apply(reformatCommand)
+
+          val firstReformat = getProjectFiles(ScalafmtTestModule.core, eval)
+
+          assert(
+            firstReformat("Main.scala").modifyTime > before("Main.scala").modifyTime,
+            firstReformat("Main.scala").content != before("Main.scala").content,
+            firstReformat("Person.scala").modifyTime > before("Person.scala").modifyTime,
+            firstReformat("Person.scala").content != before("Person.scala").content,
+            // resources files aren't modified
+            firstReformat("application.conf").modifyTime == before(
+              "application.conf").modifyTime
+          )
+
+          // cached reformat
+          val Right(_) = eval.apply(reformatCommand)
+
+          val cached = getProjectFiles(ScalafmtTestModule.core, eval)
+
+          assert(
+            cached("Main.scala").modifyTime == firstReformat("Main.scala").modifyTime,
+            cached("Person.scala").modifyTime == firstReformat("Person.scala").modifyTime,
+            cached("application.conf").modifyTime == firstReformat(
+              "application.conf").modifyTime
+          )
+
+          // reformat after change
+          write.over(cached("Main.scala").path,
+                     cached("Main.scala").content + "\n object Foo")
+
+          val Right(_) = eval.apply(reformatCommand)
+
+          val afterChange = getProjectFiles(ScalafmtTestModule.core, eval)
+
+          assert(
+            afterChange("Main.scala").modifyTime > cached("Main.scala").modifyTime,
+            afterChange("Person.scala").modifyTime == cached("Person.scala").modifyTime,
+            afterChange("application.conf").modifyTime == cached(
+              "application.conf").modifyTime
+          )
+        }
+
+      'reformat - checkReformat(ScalafmtTestModule.core.reformat())
+      'reformatAll - checkReformat(
+        ScalafmtModule.reformatAll(Tasks(Seq(ScalafmtTestModule.core.sources))))
+    }
+  }
+
+  case class FileInfo(content: String, modifyTime: Long, path: Path)
+
+  def getProjectFiles(m: ScalaModule, eval: TestEvaluator[_]) = {
+    val Right((sources, _)) = eval.apply(m.sources)
+    val Right((resources, _)) = eval.apply(m.resources)
+
+    val sourcesFiles = sources.flatMap(p => ls.rec(p.path))
+    val resourcesFiles = resources.flatMap(p => ls.rec(p.path))
+    (sourcesFiles ++ resourcesFiles).map { p =>
+      p.name -> FileInfo(read(p), p.mtime.toMillis, p)
+    }.toMap
+  }
+
+}