Scalafmt plugin implementation (#156)

* scalariform: improve logging, declare tasks final

* scalafmt plugin implementation

* add scalafmt and scalariform plugins and examples to tests

* fix logging guarded logging behaviour

* add notes about formatting check to README

* fix compilation error in examples

2 files changed, 78 insertions, 0 deletions

diff --git a/plugins/scalafmt/Scalafmt.scala b/plugins/scalafmt/Scalafmt.scala
new file mode 100644
index 0000000..94670cb
--- /dev/null
+++ b/plugins/scalafmt/Scalafmt.scala
@@ -0,0 +1,69 @@
+package cbt
+
+import org.scalafmt.{FormatResult, ScalafmtStyle}
+
+import java.io.File
+import java.nio.file.Files._
+import java.nio.file.{FileSystems, Path}
+
+/**
+  * This plugin provides scalafmt support for cbt.
+  *
+  */
+trait Scalafmt extends BaseBuild {
+  /**
+    * Reformat scala source code according to `scalafmtConfig` rules
+    *
+    * @return always returns `ExitCode.Success`
+    */
+  final def scalafmt: ExitCode = {
+    Scalafmt.format(sourceFiles, scalafmtConfig)
+    ExitCode.Success
+  }
+
+  /**
+    * Scalafmt formatting config
+    */
+  def scalafmtConfig: ScalafmtStyle = Scalafmt.defaultConfig
+}
+
+object Scalafmt {
+
+  val defaultConfig = ScalafmtStyle.default
+
+  def format(files: Seq[File], style: ScalafmtStyle): Unit = {
+    var reformattedCount: Int = 0
+    scalaSourceFiles(files) foreach { path =>
+      handleFormatted(path, style) { case (original, result) =>
+        result match {
+          case FormatResult.Success(formatted) =>
+            if (original != formatted) {
+              write(path, formatted.getBytes)
+              reformattedCount += 1
+            }
+          case FormatResult.Failure(e) =>
+            System.err.println(s"Failed to format file: $path, cause: ${e}")
+          case FormatResult.Incomplete(e) =>
+            System.err.println(s"Couldn't complete file reformat: $path")
+        }
+      }
+    }
+    if (reformattedCount > 0) System.err.println(s"Formatted $reformattedCount Scala sources")
+  }
+
+  private val scalaFileMatcher = FileSystems.getDefault.getPathMatcher("glob:**.scala")
+
+  private def scalaSourceFiles(files: Seq[File]): Seq[Path] = {
+    files collect {
+      case f if f.exists
+        && scalaFileMatcher.matches(f.toPath) => f.toPath
+    }
+  }
+
+  private def handleFormatted[T](path: Path, style: ScalafmtStyle)(handler: (String, FormatResult) => T): T = {
+    val original = new String(readAllBytes(path))
+    val result = org.scalafmt.Scalafmt.format(original, style)
+    handler(original, result)
+  }
+
+}
diff --git a/plugins/scalafmt/build/build.scala b/plugins/scalafmt/build/build.scala
new file mode 100644
index 0000000..e8ce270
--- /dev/null
+++ b/plugins/scalafmt/build/build.scala
@@ -0,0 +1,9 @@
+import cbt._
+
+class Build(val context: Context) extends Plugin {
+  override def dependencies =
+    super.dependencies ++
+    Resolver( mavenCentral ).bind(
+      ScalaDependency("com.geirsson", "scalafmt", "0.2.5")
+    )
+}