Enable warnings in build.sc, overhaul Agg to avoid triggering spurious deprecation warnings

main/api/src/mill/api/AggWrapper.scala

@@ -1,7 +1,6 @@
 package mill.api
 
-import scala.annotation.nowarn
-import scala.collection.mutable
+import scala.collection.{IterableFactory, IterableOps, mutable}
 import scala.language.implicitConversions
 
 object Strict extends AggWrapper(true)
@@ -14,26 +13,37 @@ private[mill] sealed class AggWrapper(strictUniqueness: Boolean) {
    * ordering. Raises an exception if a duplicate is found; call
    * `toSeq.distinct` if you explicitly want to make it swallow duplicates
    */
-  trait Agg[V] extends IterableOnce[V] {
+  trait Agg[V]
+      extends IterableOnce[V]
+      with IterableOps[V, Agg, Agg[V]] {
+
+    override def iterableFactory: IterableFactory[Agg]
+
+    override def fromSpecific(coll: IterableOnce[V]): Agg[V] = fromSpecific0(coll)
+    protected def fromSpecific0(coll: IterableOnce[V]): Agg[V]
+
+    override def newSpecificBuilder: scala.collection.mutable.Builder[V, Agg[V]] =
+      newSpecificBuilder0
+    protected def newSpecificBuilder0: scala.collection.mutable.Builder[V, Agg[V]]
+
     def contains(v: V): Boolean
     def items: Iterator[V]
     def indexed: IndexedSeq[V]
     def flatMap[T](f: V => IterableOnce[T]): Agg[T]
     def map[T](f: V => T): Agg[T]
     def filter(f: V => Boolean): Agg[V]
-    def withFilter(f: V => Boolean): Agg[V]
+
     def collect[T](f: PartialFunction[V, T]): Agg[T]
     def zipWithIndex: Agg[(V, Int)]
     def reverse: Agg[V]
     def zip[T](other: Agg[T]): Agg[(V, T)]
     def ++[T >: V](other: IterableOnce[T]): Agg[T]
     def length: Int
     def isEmpty: Boolean
-    def nonEmpty: Boolean = !isEmpty
     def foreach[U](f: V => U): Unit
   }
 
-  object Agg {
+  object Agg extends IterableFactory[Agg] {
     def empty[V]: Agg[V] = new Agg.Mutable[V]
     implicit def jsonFormat[T: upickle.default.ReadWriter]: upickle.default.ReadWriter[Agg[T]] =
       upickle.default
@@ -43,79 +53,107 @@ private[mill] sealed class AggWrapper(strictUniqueness: Boolean) {
           Agg.from(_)
         )
 
-    def apply[V](items: V*): Agg[V] = from(items)
+    implicit def from[V](items: IterableOnce[V]): Agg[V] = Mutable.from(items)
+    object Mutable {
+      implicit def from[V](items: IterableOnce[V]): Mutable[V] = {
+        val set = new Agg.Mutable[V]()
+        items.iterator.foreach(set.append)
+        set
+      }
+
+      def newBuilder[V] = new mutable.Builder[V, Mutable[V]] {
+        var mutable = new Agg.Mutable[V]()
+        def clear(): Unit = { mutable = new Agg.Mutable[V]() }
+        def result(): Mutable[V] = mutable
 
-    implicit def from[V](items: IterableOnce[V]): Agg[V] = {
-      val set = new Agg.Mutable[V]()
-      items.iterator.foreach(set.append)
-      set
+        def addOne(elem: V): this.type = {
+          mutable.append(elem)
+          this
+        }
+      }
     }
 
     class Mutable[V]() extends Agg[V] {
+      def iterableFactory: IterableFactory[Mutable] = new IterableFactory[Mutable] {
+        def from[A](source: IterableOnce[A]): Mutable[A] = Mutable.from(source)
+        def empty[A]: Mutable[A] = new Mutable[A]()
+        def newBuilder[A]: mutable.Builder[A, Mutable[A]] = Mutable.newBuilder[A]
+      }
+
+      protected def fromSpecific0(coll: IterableOnce[V]): Mutable[V] = from(coll)
+      protected def newSpecificBuilder0: mutable.Builder[V, Agg[V]] = {
+        Mutable.newBuilder[V]
+      }
 
       private[this] val set0 = mutable.LinkedHashSet.empty[V]
-      def contains(v: V): Boolean = set0.contains(v)
-      def append(v: V): AnyVal =
+
+      def contains(v: V) = set0.contains(v)
+      def coll = this
+
+      override def toIterable: Iterable[V] = set0.toIterable
+      def append(v: V): AnyVal = {
         if (!contains(v)) {
           set0.add(v)
 
         } else if (strictUniqueness) {
           throw new Exception("Duplicated item inserted into OrderedSet: " + v)
         }
+      }
+
       def appendAll(vs: Seq[V]): Unit = vs.foreach(append)
       def items: Iterator[V] = set0.iterator
       def indexed: IndexedSeq[V] = items.toIndexedSeq
-      def set: collection.Set[V] = set0
 
-      def map[T](f: V => T): Agg[T] = {
+      override def map[T](f: V => T): Mutable[T] = {
         val output = new Agg.Mutable[T]
         for (i <- items) output.append(f(i))
         output
       }
-      def flatMap[T](f: V => IterableOnce[T]): Agg[T] = {
+
+      override def flatMap[T](f: V => IterableOnce[T]): Mutable[T] = {
         val output = new Agg.Mutable[T]
         for (i <- items) for (i0 <- f(i).iterator) output.append(i0)
         output
       }
-      def filter(f: V => Boolean): Agg[V] = {
+
+      override def filter(f: V => Boolean): Mutable[V] = {
         val output = new Agg.Mutable[V]
         for (i <- items) if (f(i)) output.append(i)
         output
       }
-      def withFilter(f: V => Boolean): Agg[V] = filter(f)
 
-      def collect[T](f: PartialFunction[V, T]): Agg[T] =
-        this.filter(f.isDefinedAt).map(x => f(x))
+      protected def withFilter0(f: V => Boolean): collection.WithFilter[V, Mutable] =
+        new collection.WithFilter[V, Mutable] {
+          lazy val filtered = filter(f)
+          override def map[B](f: V => B): Mutable[B] = filtered.map(f)
 
-      def zipWithIndex: Agg[(V, Int)] = {
-        var i = 0
-        this.map { x =>
-          i += 1
-          (x, i - 1)
+          override def flatMap[B](f: V => IterableOnce[B]): Mutable[B] = filtered.flatMap(f)
+
+          override def foreach[U](f: V => U): Unit = filtered.foreach(f)
+
+          override def withFilter(q: V => Boolean): collection.WithFilter[V, Mutable] =
+            filtered.withFilter0(f)
         }
-      }
 
-      def reverse: Agg[V] = Agg.from(indexed.reverseIterator)
+      override def reverse: Mutable[V] = Mutable.from(indexed.reverseIterator)
 
-      def zip[T](other: Agg[T]): Agg[(V, T)] = Agg.from(items.zip(other.items))
-      def ++[T >: V](other: IterableOnce[T]): Agg[T] = Agg.from(items ++ other)
+      def zip[T](other: Agg[T]): Mutable[(V, T)] = Mutable.from(items.zip(other.items))
       def length: Int = set0.size
 
-      def exists(p: V => Boolean): Boolean = items.exists(p)
-      def find(p: V => Boolean): Option[V] = items.find(p)
-      def forall(p: V => Boolean): Boolean = items.forall(p)
-      def foreach[U](f: V => U): Unit = items.foreach(f)
-      def isEmpty: Boolean = items.isEmpty
-      def seq: scala.collection.IterableOnce[V] = items
+      override def exists(p: V => Boolean): Boolean = items.exists(p)
+      override def find(p: V => Boolean): Option[V] = items.find(p)
+      override def forall(p: V => Boolean): Boolean = items.forall(p)
+      override def foreach[U](f: V => U): Unit = items.foreach(f)
+      override def isEmpty: Boolean = items.isEmpty
       def iterator: Iterator[V] = items
-
       override def hashCode(): Int = items.map(_.hashCode()).sum
       override def equals(other: Any): Boolean = other match {
         case s: Agg[_] => items.sameElements(s.items)
         case _ => super.equals(other)
       }
       override def toString: String = items.mkString("Agg(", ", ", ")")
-
     }
+
+    override def newBuilder[A]: mutable.Builder[A, Agg[A]] = Mutable.newBuilder[A]
   }
 }

runner/src/mill/runner/MillBuildRootModule.scala

@@ -157,7 +157,7 @@ class MillBuildRootModule()(implicit
     super.scalacOptions() ++
       Seq(
         "-Xplugin:" + lineNumberPluginClasspath().map(_.path).mkString(","),
-        "-nowarn",
+        "-deprecation",
         // Make sure we abort of the plugin is not found, to ensure any
         // classpath/plugin-discovery issues are surfaced early rather than
         // after hours of debugging