Give Scoped a default equals/hashCode implementation

build.sbt

@@ -432,6 +432,10 @@ lazy val mainSettingsProj = (project in file("main-settings"))
     mimaSettings,
     mimaBinaryIssueFilters ++= Seq(
       exclude[DirectMissingMethodProblem]("sbt.Scope.display012StyleMasked"),
+
+      // added a method to a sealed trait
+      exclude[InheritedNewAbstractMethodProblem]("sbt.Scoped.canEqual"),
+      exclude[InheritedNewAbstractMethodProblem]("sbt.ScopedTaskable.canEqual"),
     ),
   )
   .configure(

main-settings/src/main/scala/sbt/Structure.scala

@@ -17,7 +17,18 @@ import sbt.Def.{ Initialize, KeyedInitialize, ScopedKey, Setting, setting }
 import std.TaskExtra.{ task => mktask, _ }
 
 /** An abstraction on top of Settings for build configuration and task definition. */
-sealed trait Scoped { def scope: Scope; val key: AttributeKey[_] }
+sealed trait Scoped extends Equals {
+  def scope: Scope
+  val key: AttributeKey[_]
+
+  override def equals(that: Any) =
+    (this eq that.asInstanceOf[AnyRef]) || (that match {
+      case that: Scoped => scope == that.scope && key == that.key && canEqual(that)
+      case _            => false
+    })
+
+  override def hashCode() = (scope, key).##
+}
 
 /** A common type for SettingKey and TaskKey so that both can be used as inputs to tasks.*/
 sealed trait ScopedTaskable[T] extends Scoped {
@@ -95,6 +106,8 @@ sealed abstract class SettingKey[T]
 
   final def withRank(rank: Int): SettingKey[T] =
     SettingKey(AttributeKey.copyWithRank(key, rank))
+
+  def canEqual(that: Any): Boolean = that.isInstanceOf[SettingKey[_]]
 }
 
 /**
@@ -163,6 +176,8 @@ sealed abstract class TaskKey[T]
 
   final def withRank(rank: Int): TaskKey[T] =
     TaskKey(AttributeKey.copyWithRank(key, rank))
+
+  def canEqual(that: Any): Boolean = that.isInstanceOf[TaskKey[_]]
 }
 
 /**
@@ -195,6 +210,8 @@ sealed trait InputKey[T]
 
   final def withRank(rank: Int): InputKey[T] =
     InputKey(AttributeKey.copyWithRank(key, rank))
+
+  def canEqual(that: Any): Boolean = that.isInstanceOf[InputKey[_]]
 }
 
 /** Methods and types related to constructing settings, including keys, scopes, and initializations. */

main-settings/src/test/scala/sbt/BuildSettingsInstances.scala

@@ -92,9 +92,13 @@ object BuildSettingsInstances {
 
   type Key = K forSome { type K <: Scoped.ScopingSetting[K] with Scoped }
 
-  def genInputKey[A: Manifest]: Gen[InputKey[A]] = Gen.identifier map (InputKey[A](_))
-  def genSettingKey[A: Manifest]: Gen[SettingKey[A]] = Gen.identifier map (SettingKey[A](_))
-  def genTaskKey[A: Manifest]: Gen[TaskKey[A]] = Gen.identifier map (TaskKey[A](_))
+  final case class Label(value: String)
+  val genLabel: Gen[Label] = Gen.identifier map Label
+  implicit def arbLabel: Arbitrary[Label] = Arbitrary(genLabel)
+
+  def genInputKey[A: Manifest]: Gen[InputKey[A]] = genLabel map (x => InputKey[A](x.value))
+  def genSettingKey[A: Manifest]: Gen[SettingKey[A]] = genLabel map (x => SettingKey[A](x.value))
+  def genTaskKey[A: Manifest]: Gen[TaskKey[A]] = genLabel map (x => TaskKey[A](x.value))
 
   def withScope[K <: Scoped.ScopingSetting[K]](keyGen: Gen[K]): Arbitrary[K] = Arbitrary {
     Gen.frequency(

main-settings/src/test/scala/sbt/ScopedSpec.scala

@@ -0,0 +1,145 @@
+/*
+ * sbt
+ * Copyright 2011 - 2017, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under BSD-3-Clause license (see LICENSE)
+ */
+
+package sbt.test
+
+import org.scalacheck._, Prop._, util.Pretty
+
+import sbt.internal.util.AttributeKey
+import sbt.util.NoJsonWriter
+import sbt.{ InputTask, Scope, Task }
+import sbt.{ InputKey, Scoped, SettingKey, TaskKey }
+
+import BuildSettingsInstances._
+
+object ScopedSpec extends Properties("Scoped") {
+  val intManifest = manifest[Int]
+  val stringManifest = manifest[String]
+
+  implicit val arbManifest: Arbitrary[Manifest[_]] =
+    Arbitrary(Gen.oneOf(intManifest, stringManifest))
+
+  property("setting keys are structurally equal") = {
+    forAll { (label: Label, manifest: Manifest[_], scope: Scope) =>
+      val k1 = settingKey(label, manifest, scope)
+      val k2 = settingKey(label, manifest, scope)
+      expectEq(k1, k2)
+    }
+  }
+
+  property("task keys are structurally equal") = {
+    forAll { (label: Label, manifest: Manifest[_], scope: Scope) =>
+      val k1 = taskKey(label, manifest, scope)
+      val k2 = taskKey(label, manifest, scope)
+      expectEq(k1, k2)
+    }
+  }
+
+  property("input keys are structurally equal") = {
+    forAll { (label: Label, manifest: Manifest[_], scope: Scope) =>
+      val k1 = inputKey(label, manifest, scope)
+      val k2 = inputKey(label, manifest, scope)
+      expectEq(k1, k2)
+    }
+  }
+
+  property("different key types are not equal") = {
+    forAll { (label: Label, manifest: Manifest[_], scope: Scope) =>
+      val settingKey1 = settingKey(label, manifest, scope)
+      val taskKey1 = taskKey(label, manifest, scope)
+      val inputKey1 = inputKey(label, manifest, scope)
+
+      all(
+        expectNe(settingKey1, taskKey1),
+        expectNe(settingKey1, inputKey1),
+        expectNe(taskKey1, inputKey1),
+      )
+    }
+  }
+
+  property("different key types, with the same manifest, are not equal") = {
+    forAll { (label: Label, scope: Scope) =>
+      val prop1 = {
+        val manifest1 = manifest[Task[String]]
+        val attrKey = attributeKey(label, manifest1)
+        val k1 = SettingKey(attrKey) in scope
+        val k2 = TaskKey(attrKey) in scope
+        expectNeSameManifest(k1, k2)
+      }
+
+      val prop2 = {
+        val manifest1 = manifest[InputTask[String]]
+        val attrKey = attributeKey(label, manifest1)
+        val k1 = SettingKey(attrKey) in scope
+        val k2 = InputKey(attrKey) in scope
+        expectNeSameManifest(k1, k2)
+      }
+
+      all(prop1, prop2)
+    }
+  }
+
+  ///
+
+  def settingKey[A](label: Label, manifest: Manifest[A], scope: Scope): SettingKey[A] = {
+    val noJsonWriter = NoJsonWriter[A]()
+    SettingKey[A](label.value)(manifest, noJsonWriter) in scope
+  }
+
+  def taskKey[A](label: Label, manifest: Manifest[A], s: Scope): TaskKey[A] =
+    TaskKey[A](label.value)(manifest) in s
+
+  def inputKey[A](label: Label, manifest: Manifest[A], scope: Scope): InputKey[A] =
+    InputKey[A](label.value)(manifest) in scope
+
+  def attributeKey[A](label: Label, manifest: Manifest[A]): AttributeKey[A] = {
+    val jsonWriter = NoJsonWriter[A]()
+    AttributeKey[A](label.value)(manifest, jsonWriter)
+  }
+
+  ///
+
+  def expectEq(k1: Scoped, k2: Scoped): Prop =
+    ?=(k1, k2) && ?=(k2, k1) map eqLabels(k1, k2)
+
+  def expectNe(k1: Scoped, k2: Scoped): Prop =
+    !=(k1, k2) && !=(k2, k1) map eqLabels(k1, k2)
+
+  def expectNeSameManifest(k1: Scoped, k2: Scoped) = {
+    all(
+      ?=(k1.key.manifest, k2.key.manifest), // sanity check the manifests are the same
+      expectNe(k1, k2),
+    )
+  }
+
+  def eqLabels(k1: Scoped, k2: Scoped): Prop.Result => Prop.Result = r => {
+    val eqLabel = k1.key.label == k2.key.label
+    val eqManifest = k1.key.manifest == k2.key.manifest
+    val eqScope = k1.scope == k2.scope
+    r.label(s"label equality: ${k1.key.label} == ${k2.key.label} : $eqLabel")
+      .label(s"manifest equality: ${k1.key.manifest} == ${k2.key.manifest} : $eqManifest")
+      .label(s"scope equality: ${k1.scope} == ${k2.scope} : $eqScope")
+  }
+
+  def ?=[T](x: T, y: T)(implicit pp: T => Pretty): Prop =
+    if (x == y) proved
+    else
+      falsified :| {
+        val act = Pretty.pretty[T](x, Pretty.Params(0))
+        val exp = Pretty.pretty[T](y, Pretty.Params(0))
+        s"Expected $act to be equal to $exp"
+      }
+
+  def !=[T](x: T, y: T)(implicit pp: T => Pretty): Prop =
+    if (x == y) falsified
+    else
+      proved :| {
+        val act = Pretty.pretty[T](x, Pretty.Params(0))
+        val exp = Pretty.pretty[T](y, Pretty.Params(0))
+        s"Expected $act to NOT be equal to $exp"
+      }
+}

project/plugins.sbt

@@ -1,6 +1,7 @@
 scalaVersion := "2.12.4"
 scalacOptions ++= Seq("-feature", "-language:postfixOps")
 
+addSbtPlugin("com.typesafe"      % "sbt-mima-plugin" % "0.2.0")
 addSbtPlugin("org.scala-sbt"     % "sbt-houserules"  % "0.3.5")
 addSbtPlugin("org.scala-sbt"     % "sbt-contraband"  % "0.3.2")
 addSbtPlugin("de.heikoseeberger" % "sbt-header"      % "3.0.2")