switch to using sjson-new-murmurhash

The input validation for caching currently relies on having a stack of `scala.math.Equiv`, which is questionable since it can fallback to universal equality.

This is likely related to the intermittent caching behavior we are seeing in https://github.com/sbt/sbt/issues/3226

build.sbt

@@ -113,7 +113,7 @@ lazy val utilCache = (project in file("util-cache")).
   settings(
     commonSettings,
     name := "Util Cache",
-    libraryDependencies ++= Seq(sjsonnewScalaJson.value, scalaReflect.value)
+    libraryDependencies ++= Seq(sjsonnewScalaJson.value, sjsonnewMurmurhash.value, scalaReflect.value)
   ).
   configure(addSbtIO)
 

project/Dependencies.scala

@@ -46,6 +46,7 @@ object Dependencies {
 
   val sjsonnew = Def.setting { "com.eed3si9n" %% "sjson-new-core" % contrabandSjsonNewVersion.value }
   val sjsonnewScalaJson = Def.setting { "com.eed3si9n" %% "sjson-new-scalajson" % contrabandSjsonNewVersion.value }
+  val sjsonnewMurmurhash = Def.setting { "com.eed3si9n" %% "sjson-new-murmurhash" % contrabandSjsonNewVersion.value }
 
   def log4jVersion = "2.8.1"
   val log4jApi = "org.apache.logging.log4j" % "log4j-api" % log4jVersion

util-cache/src/main/scala/sbt/util/BasicCacheImplicits.scala

@@ -1,56 +1,18 @@
 package sbt.util
 
-import java.net.{ URI, URL }
-
 import sjsonnew.{ BasicJsonProtocol, JsonFormat }
 
 trait BasicCacheImplicits { self: BasicJsonProtocol =>
 
-  implicit def basicCache[I: JsonFormat: Equiv, O: JsonFormat]: Cache[I, O] =
+  implicit def basicCache[I: JsonFormat, O: JsonFormat]: Cache[I, O] =
     new BasicCache[I, O]()
 
-  def defaultEquiv[T]: Equiv[T] =
-    new Equiv[T] { def equiv(a: T, b: T) = a == b }
-
-  def wrapEquiv[S, T](f: S => T)(implicit eqT: Equiv[T]): Equiv[S] =
-    new Equiv[S] {
-      def equiv(a: S, b: S) =
-        eqT.equiv(f(a), f(b))
-    }
-
-  implicit def optEquiv[T](implicit t: Equiv[T]): Equiv[Option[T]] =
-    new Equiv[Option[T]] {
-      def equiv(a: Option[T], b: Option[T]) =
-        (a, b) match {
-          case (None, None)         => true
-          case (Some(va), Some(vb)) => t.equiv(va, vb)
-          case _                    => false
-        }
-    }
-  implicit def urlEquiv(implicit uriEq: Equiv[URI]): Equiv[URL] = wrapEquiv[URL, URI](_.toURI)(uriEq)
-  implicit def uriEquiv: Equiv[URI] = defaultEquiv
-  implicit def stringSetEquiv: Equiv[Set[String]] = defaultEquiv
-  implicit def stringMapEquiv: Equiv[Map[String, String]] = defaultEquiv
-
-  implicit def arrEquiv[T](implicit t: Equiv[T]): Equiv[Array[T]] =
-    wrapEquiv((x: Array[T]) => x: Seq[T])(seqEquiv[T](t))
-
-  implicit def seqEquiv[T](implicit t: Equiv[T]): Equiv[Seq[T]] =
-    new Equiv[Seq[T]] {
-      def equiv(a: Seq[T], b: Seq[T]) =
-        a.length == b.length &&
-          ((a, b).zipped forall t.equiv)
-    }
-
   def wrapIn[I, J](implicit f: I => J, g: J => I, jCache: SingletonCache[J]): SingletonCache[I] =
     new SingletonCache[I] {
       override def read(from: Input): I = g(jCache.read(from))
       override def write(to: Output, value: I) = jCache.write(to, f(value))
-      override def equiv: Equiv[I] = wrapEquiv(f)(jCache.equiv)
     }
 
   def singleton[T](t: T): SingletonCache[T] =
-    SingletonCache.basicSingletonCache(asSingleton(t), trueEquiv)
-
-  def trueEquiv[T] = new Equiv[T] { def equiv(a: T, b: T) = true }
+    SingletonCache.basicSingletonCache(asSingleton(t))
 }

util-cache/src/main/scala/sbt/util/Cache.scala

@@ -73,13 +73,5 @@ object Cache {
         println(label + ".write: " + value)
         cache.write(to, value)
       }
-
-      override def equiv: Equiv[I] = new Equiv[I] {
-        def equiv(a: I, b: I) = {
-          val equ = cache.equiv.equiv(a, b)
-          println(label + ".equiv(" + a + ", " + b + "): " + equ)
-          equ
-        }
-      }
     }
 }

util-cache/src/main/scala/sbt/util/SeparatedCache.scala

@@ -6,58 +6,54 @@ package sbt.util
 import scala.util.Try
 
 import sjsonnew.JsonFormat
+import sjsonnew.support.murmurhash.Hasher
 
 import CacheImplicits._
 
 /**
  * A cache that stores a single value.
  */
-trait SingletonCache[T] {
+trait SingletonCache[A] {
   /** Reads the cache from the backing `from`. */
-  def read(from: Input): T
+  def read(from: Input): A
 
   /** Writes `value` to the backing `to`. */
-  def write(to: Output, value: T): Unit
-
-  /** Equivalence for elements of type `T`. */
-  def equiv: Equiv[T]
+  def write(to: Output, value: A): Unit
 }
 
 object SingletonCache {
 
-  implicit def basicSingletonCache[T: JsonFormat: Equiv]: SingletonCache[T] =
-    new SingletonCache[T] {
-      override def read(from: Input): T = from.read[T]
-      override def write(to: Output, value: T) = to.write(value)
-      override def equiv: Equiv[T] = implicitly
+  implicit def basicSingletonCache[A: JsonFormat]: SingletonCache[A] =
+    new SingletonCache[A] {
+      override def read(from: Input): A = from.read[A]
+      override def write(to: Output, value: A) = to.write(value)
     }
 
   /** A lazy `SingletonCache` */
-  def lzy[T: JsonFormat: Equiv](mkCache: => SingletonCache[T]): SingletonCache[T] =
-    new SingletonCache[T] {
+  def lzy[A: JsonFormat](mkCache: => SingletonCache[A]): SingletonCache[A] =
+    new SingletonCache[A] {
       lazy val cache = mkCache
-      override def read(from: Input): T = cache.read(from)
-      override def write(to: Output, value: T) = cache.write(to, value)
-      override def equiv = cache.equiv
+      override def read(from: Input): A = cache.read(from)
+      override def write(to: Output, value: A) = cache.write(to, value)
     }
 }
 
 /**
  * Simple key-value cache.
  */
-class BasicCache[I: JsonFormat: Equiv, O: JsonFormat] extends Cache[I, O] {
-  private val singletonCache: SingletonCache[(I, O)] = implicitly
-  val equiv: Equiv[I] = implicitly
-  override def apply(store: CacheStore)(key: I): CacheResult[O] =
+class BasicCache[I: JsonFormat, O: JsonFormat] extends Cache[I, O] {
+  private val singletonCache: SingletonCache[(Long, O)] = implicitly
+  val jsonFormat: JsonFormat[I] = implicitly
+  override def apply(store: CacheStore)(key: I): CacheResult[O] = {
+    val keyHash: Long = Hasher.hashUnsafe[I](key).toLong
     Try {
-      val (previousKey, previousValue) = singletonCache.read(store)
-      if (equiv.equiv(key, previousKey))
-        Hit(previousValue)
-      else
-        Miss(update(store)(key))
-    } getOrElse Miss(update(store)(key))
+      val (previousKeyHash, previousValue) = singletonCache.read(store)
+      if (keyHash == previousKeyHash) Hit(previousValue)
+      else Miss(update(store)(keyHash))
+    } getOrElse Miss(update(store)(keyHash))
+  }
 
-  private def update(store: CacheStore)(key: I) = (value: O) => {
-    singletonCache.write(store, (key, value))
+  private def update(store: CacheStore)(keyHash: Long) = (value: O) => {
+    singletonCache.write(store, (keyHash, value))
   }
 }

util-tracking/src/main/scala/sbt/util/Tracked.scala

@@ -10,11 +10,9 @@ import sbt.io.IO
 import sbt.io.syntax._
 
 import sjsonnew.JsonFormat
+import sjsonnew.support.murmurhash.Hasher
 
 object Tracked {
-
-  import CacheImplicits.LongJsonFormat
-
   /**
    * Creates a tracker that provides the last time it was evaluated.
    * If the function throws an exception.
@@ -33,7 +31,10 @@ object Tracked {
    * If 'useStartTime' is false, the recorded time is when the evaluated function completes.
    * In both cases, the timestamp is not updated if the function throws an exception.
    */
-  def tstamp(store: CacheStore, useStartTime: Boolean): Timestamp = new Timestamp(store, useStartTime)
+  def tstamp(store: CacheStore, useStartTime: Boolean): Timestamp = {
+    import CacheImplicits.LongJsonFormat
+    new Timestamp(store, useStartTime)
+  }
 
   /**
    * Creates a tracker that provides the last time it was evaluated.
@@ -74,7 +75,10 @@ object Tracked {
    * recent invocation.
    */
   def inputChanged[I: JsonFormat: SingletonCache, O](store: CacheStore)(f: (Boolean, I) => O): I => O = { in =>
-    val cache: SingletonCache[I] = implicitly
+    val cache: SingletonCache[Long] = {
+      import CacheImplicits.LongJsonFormat
+      implicitly
+    }
     val help = new CacheHelp(cache)
     val changed = help.changed(store, in)
     val result = f(changed, in)
@@ -90,14 +94,19 @@ object Tracked {
   def inputChanged[I: JsonFormat: SingletonCache, O](cacheFile: File)(f: (Boolean, I) => O): I => O =
     inputChanged(CacheStore(cacheFile))(f)
 
-  private final class CacheHelp[I: JsonFormat](val sc: SingletonCache[I]) {
+  private final class CacheHelp[I: JsonFormat](val sc: SingletonCache[Long]) {
+    import CacheImplicits.implicitHashWriter
     def save(store: CacheStore, value: I): Unit = {
       store.write(value)
     }
 
     def changed(store: CacheStore, value: I): Boolean =
       Try { store.read[I] } match {
-        case Success(prev) => !sc.equiv.equiv(value, prev)
+        case Success(prev) =>
+          Hasher.hash(value) match {
+            case Success(keyHash) => keyHash.toLong != prev
+            case Failure(_)       => true
+          }
         case Failure(_) => true
       }
   }