Implement remote test caching

main/src/main/scala/sbt/Defaults.scala

@@ -1413,8 +1413,8 @@ object Defaults extends BuildCommon {
             Keys.logLevel.?.value.getOrElse(stateLogLevel),
           ) +:
             TestStatusReporter(
-              IncrementalTest.succeededFile((test / streams).value.cacheDirectory),
               definedTestDigests.value,
+              Def.cacheConfiguration.value,
             ) +:
             (TaskZero / testListeners).value
         },

main/src/main/scala/sbt/RemoteCache.scala

@@ -197,7 +197,6 @@ object RemoteCache {
   ) ++ inConfig(Compile)(
     configCacheSettings(compileArtifact(Compile, cachedCompileClassifier))
   )
-    ++ inConfig(Test)(configCacheSettings(testArtifact(Test, cachedTestClassifier))))
 
   def getResourceFilePaths() = Def.task {
     val syncDir = crossTarget.value / (prefix(configuration.value.name) + "sync")
@@ -383,19 +382,6 @@ object RemoteCache {
     )
   }
 
-  def testArtifact(
-      configuration: Configuration,
-      classifier: String
-  ): Def.Initialize[Task[TestRemoteCacheArtifact]] = Def.task {
-    TestRemoteCacheArtifact(
-      Artifact(moduleName.value, classifier),
-      configuration / packageCache,
-      (configuration / classDirectory).value,
-      (configuration / compileAnalysisFile).value,
-      IncrementalTest.succeededFile((configuration / test / streams).value.cacheDirectory)
-    )
-  }
-
   private def toVersion(v: String): String = s"0.0.0-$v"
 
   private lazy val doption = new DownloadOptions

main/src/main/scala/sbt/internal/IncrementalTest.scala

@@ -20,7 +20,7 @@ import sbt.io.syntax.*
 import sbt.io.{ GlobFilter, IO, NameFilter }
 import sbt.protocol.testing.TestResult
 import sbt.SlashSyntax0.*
-import sbt.util.Digest
+import sbt.util.{ ActionCache, BuildWideCacheConfiguration, CacheLevelTag, Digest }
 import sbt.util.CacheImplicits.given
 import scala.collection.concurrent
 import scala.collection.mutable
@@ -33,10 +33,13 @@ object IncrementalTest:
       val cp = (Keys.test / fullClasspath).value
       val s = (Keys.test / streams).value
       val digests = (Keys.definedTestDigests).value
-      val succeeded = TestStatus.read(succeededFile(s.cacheDirectory))
-      def hasSucceeded(className: String): Boolean = succeeded.get(className) match
+      val config = Def.cacheConfiguration.value
+      def hasCachedSuccess(ts: Digest): Boolean =
+        val input = cacheInput(ts)
+        ActionCache.exists(input._1, input._2, input._3, config)
+      def hasSucceeded(className: String): Boolean = digests.get(className) match
         case None     => false
-        case Some(ts) => Some(ts) == digests.get(className)
+        case Some(ts) => hasCachedSuccess(ts)
       args =>
         for filter <- selectedFilter(args)
         yield (test: String) => filter(test) && !hasSucceeded(test)
@@ -47,19 +50,25 @@ object IncrementalTest:
     val cp = (Keys.test / fullClasspath).value
     val testNames = Keys.definedTests.value.map(_.name).toVector.distinct
     val converter = fileConverter.value
-    val inputs = Keys.compileInputs.value
-    val extra = Digest(converter.toVirtualFile(inputs.options.classesDirectory))
+    val sv = Keys.scalaVersion.value
+    val inputs = (Keys.compile / Keys.compileInputs).value
+    // by default this captures JVM version
+    val extraInc = Keys.extraIncOptions.value
+    // throw in any information useful for runtime invalidation
+    val salt = s"""$sv
+${converter.toVirtualFile(inputs.options.classesDirectory)}
+${extraInc.mkString(",")}
+"""
+    val extra = Vector(Digest.sha256Hash(salt.getBytes("UTF-8")))
     val stamper = ClassStamper(cp, converter)
     // TODO: Potentially do something about JUnit 5 and others which might not use class name
     Map((testNames.flatMap: name =>
-      stamper.transitiveStamp(name, Vector(extra)) match
+      stamper.transitiveStamp(name, extra) match
         case Some(ts) => Seq(name -> ts)
         case None     => Nil
     ): _*)
   }
 
-  def succeededFile(dir: File): File = dir / "succeeded_tests.txt"
-
   def selectedFilter(args: Seq[String]): Seq[String => Boolean] =
     def matches(nfs: Seq[NameFilter], s: String) = nfs.exists(_.accept(s))
     val (excludeArgs, includeArgs) = args.partition(_.startsWith("-"))
@@ -70,13 +79,17 @@ object IncrementalTest:
       case (Nil, _)   => Seq((s: String) => !matches(excludeFilters, s))
       case _ =>
         includeFilters.map(f => (s: String) => (f.accept(s) && !matches(excludeFilters, s)))
+
+  private[sbt] def cacheInput(value: Digest): (Unit, Digest, Digest) =
+    ((), value, Digest.zero)
 end IncrementalTest
 
-// Assumes exclusive ownership of the file.
 private[sbt] class TestStatusReporter(
-    f: File,
     digests: Map[String, Digest],
+    cacheConfiguration: BuildWideCacheConfiguration,
 ) extends TestsListener:
+  // int value to represent success
+  private final val successfulTest = 0
   private lazy val succeeded: concurrent.Map[String, Digest] =
     TestStatus.read(f)
 
@@ -94,8 +107,20 @@ private[sbt] class TestStatusReporter(
   def endGroup(name: String, result: TestResult): Unit =
     if result == TestResult.Passed then
       digests.get(name) match
-        case Some(ts) => succeeded(name) = ts
-        case None     => succeeded(name) = Digest.zero
+        case Some(ts) =>
+          succeeded(name) = ts
+          // treat each test suite as a successful action that returns 0
+          val input = IncrementalTest.cacheInput(ts)
+          ActionCache.cache(
+            key = input._1,
+            codeContentHash = input._2,
+            extraHash = input._3,
+            tags = CacheLevelTag.all.toList,
+            config = cacheConfiguration,
+          ): (_) =>
+            ActionCache.actionResult(successfulTest)
+        case None =>
+          succeeded(name) = Digest.zero
     else ()
   def doComplete(finalResult: TestResult): Unit =
     TestStatus.write(succeeded, "Successful Tests", f)