Fix #2677: Tags.ForkedTestGroup doesn't work

Move tag to correct task

main/actions/src/main/scala/sbt/ForkTests.scala

@@ -9,9 +9,10 @@ import java.net.ServerSocket
 import java.io._
 import Tests.{ Output => TestOutput, _ }
 import ForkMain._
+import sbt.ConcurrentRestrictions.Tag
 
 private[sbt] object ForkTests {
-  def apply(runners: Map[TestFramework, Runner], tests: List[TestDefinition], config: Execution, classpath: Seq[File], fork: ForkOptions, log: Logger): Task[TestOutput] = {
+  def apply(runners: Map[TestFramework, Runner], tests: List[TestDefinition], config: Execution, classpath: Seq[File], fork: ForkOptions, log: Logger, tag: Tag): Task[TestOutput] = {
     val opts = processOptions(config, tests, log)
 
     import std.TaskExtra._
@@ -23,7 +24,7 @@ private[sbt] object ForkTests {
         constant(TestOutput(TestResult.Passed, Map.empty[String, SuiteResult], Iterable.empty))
       else
         mainTestTask(runners, opts, classpath, fork, log, config.parallel).tagw(config.tags: _*)
-    main.dependsOn(all(opts.setup): _*) flatMap { results =>
+    main.tag(tag).dependsOn(all(opts.setup): _*) flatMap { results =>
       all(opts.cleanup).join.map(_ => results)
     }
   }

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

@@ -566,7 +566,7 @@ object Defaults extends BuildCommon {
             s.log.debug(s"javaOptions: ${opts.runJVMOptions}")
             val forkedConfig = config.copy(parallel = config.parallel && forkedParallelExecution)
             s.log.debug(s"Forking tests - parallelism = ${forkedConfig.parallel}")
-            ForkTests(runners, tests.toList, forkedConfig, cp.files, opts, s.log) tag Tags.ForkedTestGroup
+            ForkTests(runners, tests.toList, forkedConfig, cp.files, opts, s.log, Tags.ForkedTestGroup)
           case Tests.InProcess =>
             if (javaOptions.nonEmpty) {
               s.log.warn("javaOptions will be ignored, fork is set to false")

sbt/src/sbt-test/tests/fork-test-group-parallel/build.sbt

@@ -0,0 +1,18 @@
+concurrentRestrictions in Global := Seq(Tags.limitAll(4))
+
+libraryDependencies += "org.specs2" %% "specs2-core" % "3.8.4" % Test
+
+inConfig(Test)(Seq(
+  testGrouping := definedTests.value.map { test => new Tests.Group(test.name, Seq(test), Tests.SubProcess(
+    ForkOptions(
+      javaHome.value,
+      outputStrategy.value,
+      Nil,
+      Some(baseDirectory.value),
+      javaOptions.value,
+      connectInput.value,
+      envVars.value
+    )
+  ))},
+  TaskKey[Unit]("test-failure") := test.failure.value
+))

sbt/src/sbt-test/tests/fork-test-group-parallel/src/test/scala/example/Test.scala

@@ -0,0 +1,23 @@
+package example
+
+import java.io.File
+import org.specs2.mutable.Specification
+
+trait Test extends Specification {
+  "spec" should {
+    "be run one at time" in {
+      val lock = new File("lock")
+      lock.mkdir() should beTrue
+      Thread.sleep(2000)
+      lock.delete() should beTrue
+    }
+  }
+}
+
+class Test0 extends Test
+
+class Test1 extends Test
+
+class Test2 extends Test
+
+class Test3 extends Test

sbt/src/sbt-test/tests/fork-test-group-parallel/test

@@ -0,0 +1,3 @@
+> test-failure
+> set concurrentRestrictions in Global += Tags.limit(Tags.ForkedTestGroup, 1)
+> test