Enable builds under GraalVM

scalafmt-cli/src/main/scala/org/scalafmt/cli/Cli.scala

@@ -63,7 +63,7 @@ object Cli {
   }
 
   def main(args: Array[String]): Unit = {
-    val exit = mainWithOptions(args, CliOptions.default)
+    val exit = mainWithOptions(args, CliOptions())
     sys.exit(exit.code)
   }
 

scalafmt-core/js/src/main/scala/org/scalafmt/internal/package.scala

@@ -0,0 +1,5 @@
+package org.scalafmt
+
+package object internal {
+  type PriorityQueue[T] = scala.collection.mutable.PriorityQueue[T]
+}

scalafmt-core/jvm/src/main/scala/org/scalafmt/internal/PriorityQueue.scala

@@ -0,0 +1,32 @@
+package org.scalafmt.internal
+
+/**
+  * Minimal implementation of the PriorityQueue's functions needed.
+  *
+  * We use [[java.util.PriorityQueue]] to enable usage under GraalVM. The
+  * native-image compiler is unable to work with
+  * [[scala.collection.mutable.PriorityQueue]] currently.
+  *
+  * @tparam T the values inside the queue
+  */
+class PriorityQueue[T](implicit ord: Ordering[T]) {
+  private[this] val q = new java.util.PriorityQueue[T](11, ord.reversed())
+
+  def dequeueAll: Unit = q.clear()
+
+  def dequeue(): T = q.poll()
+
+  def size: Int = q.size()
+
+  def enqueue(x: T): Unit = q.add(x)
+
+  def +=(x: T): PriorityQueue[T] = {
+    q.add(x)
+    this
+  }
+
+  def nonEmpty: Boolean = !isEmpty
+
+  def isEmpty: Boolean = q.isEmpty
+
+}

scalafmt-core/shared/src/main/scala/org/scalafmt/internal/BestFirstSearch.scala

@@ -151,7 +151,7 @@ class BestFirstSearch(
       stop: Token,
       depth: Int = 0,
       maxCost: Int = Integer.MAX_VALUE): State = {
-    val Q = new mutable.PriorityQueue[State]()
+    val Q = new PriorityQueue[State]()
     var result = start
     var lastDequeue = start
     Q += start