Fix cached update task

Fixes sbt/sbt#3226

One of the checks that the cached update task performs is called `depsUpdated`, which checks if the subproject dependencies have been thawed out of cache of now.
For this to function correctly, when we thaw the `UpdateReport` from JSON, we need to mark the report as cached. This was done subtley in sbt 0.13 for sbinary (https://github.com/sbt/sbt-zero-thirteen/blob/v0.13.15/main/actions/src/main/scala/sbt/CacheIvy.scala#L66-L67).

main/src/main/scala/sbt/internal/LibraryManagement.scala

@@ -71,17 +71,22 @@ object LibraryManagement {
     def skipResolve(cache: CacheStore): UpdateInputs => UpdateReport = {
       import sbt.librarymanagement.LibraryManagementCodec._
       Tracked.lastOutput[UpdateInputs, UpdateReport](cache) {
-        case (_, Some(out)) => out
+        case (_, Some(out)) => markAsCached(out)
         case _ =>
           sys.error("Skipping update requested, but update has not previously run successfully.")
       }
     }
 
+    // Mark UpdateReport#stats as "cached." This is used by the dependers later
+    // to determine whether they now need to run update in the above `upToDate`.
+    def markAsCached(ur: UpdateReport): UpdateReport =
+      ur.withStats(ur.stats.withCached(true))
+
     def doResolve(cache: CacheStore): UpdateInputs => UpdateReport = {
       val doCachedResolve = { (inChanged: Boolean, updateInputs: UpdateInputs) =>
         import sbt.librarymanagement.LibraryManagementCodec._
         val cachedResolve = Tracked.lastOutput[UpdateInputs, UpdateReport](cache) {
-          case (_, Some(out)) if upToDate(inChanged, out) => out
+          case (_, Some(out)) if upToDate(inChanged, out) => markAsCached(out)
           case _                                          => resolve(updateInputs)
         }
         import scala.util.control.Exception.catching

sbt/src/sbt-test/dependency-management/cache-update/build.sbt

@@ -1,33 +1,54 @@
-// #1620
-
-ivyPaths := IvyPaths(
-  (baseDirectory in ThisBuild).value,
-  Some((baseDirectory in LocalRootProject).value / "ivy-cache")
-)
-
-scalaVersion := "2.10.4"
-
+scalaVersion in ThisBuild        := "2.10.4"
 dependencyOverrides in ThisBuild += "com.github.nscala-time" %% "nscala-time" % "1.0.0"
-libraryDependencies              += "com.github.nscala-time" %% "nscala-time" % "1.0.0"
 
-TaskKey[Unit]("check") := {
-  val s = (streams in update).value
-  val cacheStoreFactory = s.cacheStoreFactory sub updateCacheName.value
-  val module = ivyModule.value
-  val config = updateConfiguration.value
+lazy val root = (project in file("."))
+  .dependsOn(p1 % Compile)
+  .settings(
+    ivyPaths := IvyPaths(
+      (baseDirectory in ThisBuild).value,
+      Some((baseDirectory in LocalRootProject).value / "ivy-cache")
+    ),
+    libraryDependencies += "com.github.nscala-time" %% "nscala-time" % "1.0.0",
 
-  import sbt.internal.librarymanagement.IvyConfiguration
-  import sbt.librarymanagement.{ ModuleSettings, UpdateConfiguration }
+    // https://github.com/sbt/sbt/pull/1620
+    // sbt resolves dependencies every compile when using %% with dependencyOverrides
+    TaskKey[Unit]("check") := {
+      val s = (streams in update).value
+      val cacheStoreFactory = s.cacheStoreFactory sub updateCacheName.value
+      val module = ivyModule.value
+      val config = updateConfiguration.value
 
-  type In = IvyConfiguration :+: ModuleSettings :+: UpdateConfiguration :+: HNil
+      import sbt.internal.librarymanagement.IvyConfiguration
+      import sbt.librarymanagement.{ ModuleSettings, UpdateConfiguration }
 
-  import sbt.util.CacheImplicits._
-  import sbt.internal.AltLibraryManagementCodec._
+      type In = IvyConfiguration :+: ModuleSettings :+: UpdateConfiguration :+: HNil
 
-  val f: In => Unit =
-    Tracked.inputChanged(cacheStoreFactory make "inputs") { (inChanged: Boolean, in: In) =>
-      if (inChanged)
-        sys.error(s"Update cache is invalidated: ${module.owner.configuration}, ${module.moduleSettings}, $config")
+      import sbt.util.CacheImplicits._
+      import sbt.internal.AltLibraryManagementCodec._
+
+      val f: In => Unit =
+        Tracked.inputChanged(cacheStoreFactory make "inputs") { (inChanged: Boolean, in: In) =>
+          if (inChanged)
+            sys.error(s"Update cache is invalidated: ${module.owner.configuration}, ${module.moduleSettings}, $config")
+        }
+      f(module.owner.configuration :+: module.moduleSettings :+: config :+: HNil)
+    },
+
+    // https://github.com/sbt/sbt/issues/3226
+    // update caching is not working on sbt 1.0.x
+    TaskKey[Unit]("check2") := {
+      val ur = update.value
+      if (!ur.stats.cached) {
+        sys.error(s"update.value is not cached! $ur")
+      }
+      val tu = transitiveUpdate.value
+      if (tu.exists(!_.stats.cached)) {
+        sys.error(s"uncached transitiveUpdate exists! $tu")
+      }
     }
-  f(module.owner.configuration :+: module.moduleSettings :+: config :+: HNil)
-}
+  )
+
+lazy val p1 = project
+  .settings(
+    libraryDependencies += "com.novocode" % "junit-interface" % "0.11"
+  )

sbt/src/sbt-test/dependency-management/cache-update/test

@@ -1,2 +1,3 @@
 > compile
 > check
+> check2