Verify only props matching the given TestSelectors

Previously, ScalaCheck ignored the selectors that it receives as input
in the "root task". This prevented users from running only a subset of
properties in a specification by passing their `TestSelector` to
ScalaCheck in a `TaskDef`.

This patch fixes this by having the root task program the execution of
only the requested properties if the `TaskDef` contains only
`TestSelector`s. ScalaCheck's behavior remains unchanged if the
`TaskDef` contains any other kind of `Selector`.

core/jvm/src/test/scala/org/scalacheck/ScalaCheckFrameworkSpecification.scala

@@ -0,0 +1,64 @@
+/*
+ * ScalaCheck
+ * Copyright (c) 2007-2021 Rickard Nilsson. All rights reserved.
+ * http://www.scalacheck.org
+ *
+ * This software is released under the terms of the Revised BSD License.
+ * There is NO WARRANTY. See the file LICENSE for the full text.
+ */
+
+package org.scalacheck
+
+import org.scalacheck.Prop.proved
+import sbt.testing.{Selector, SuiteSelector, TaskDef, TestSelector}
+
+object ScalaCheckFrameworkSpecification extends Properties("ScalaCheckFramework") {
+
+  private val firstProp = "ScalaCheckFrameworkHelper.first prop"
+  private val secondProp = "ScalaCheckFrameworkHelper.second prop"
+  private val thirdProp = "ScalaCheckFrameworkHelper.third prop"
+
+  property("all props with SuiteSelector") = {
+    getPropNamesForSelectors(List(new SuiteSelector)) == List(firstProp, secondProp, thirdProp)
+    getPropNamesForSelectors(List(new SuiteSelector, new TestSelector(firstProp))) == List(
+      firstProp,
+      secondProp,
+      thirdProp)
+    getPropNamesForSelectors(List(new SuiteSelector, new TestSelector("no matches"))) == List(
+      firstProp,
+      secondProp,
+      thirdProp)
+  }
+
+  property("only matching props with TestSelector") = {
+    getPropNamesForSelectors(List(new TestSelector(firstProp))) == List(firstProp)
+    getPropNamesForSelectors(List(new TestSelector(secondProp))) == List(secondProp)
+    getPropNamesForSelectors(List(new TestSelector(firstProp), new TestSelector(thirdProp))) == List(
+      firstProp,
+      thirdProp)
+    getPropNamesForSelectors(List(new TestSelector("no matches"))) == Nil
+  }
+
+  private def getPropNamesForSelectors(selectors: List[Selector]): List[String] = {
+    val framework = new ScalaCheckFramework()
+    val runner = framework.runner(Array.empty, Array.empty, getClass.getClassLoader).asInstanceOf[ScalaCheckRunner]
+    val taskDef = new TaskDef(
+      classOf[ScalaCheckFrameworkSpecificationHelper].getName,
+      framework.fingerprints()(0),
+      true,
+      selectors.toArray)
+    val baseTask = runner.rootTask(taskDef)
+    val newTasks = baseTask.execute(null, null)
+    val propNames = for {
+      task <- newTasks
+      selector <- task.taskDef().selectors()
+    } yield selector.asInstanceOf[TestSelector].testName()
+    propNames.toList
+  }
+}
+
+class ScalaCheckFrameworkSpecificationHelper extends Properties("ScalaCheckFrameworkHelper") {
+  property("first prop") = proved
+  property("second prop") = proved
+  property("third prop") = proved
+}

core/shared/src/main/scala/org/scalacheck/ScalaCheckFramework.scala

@@ -92,8 +92,14 @@ private abstract class ScalaCheckRunner extends Runner {
   }
 
   def rootTask(td: TaskDef): BaseTask = new BaseTask(td) {
-    def execute(handler: EventHandler, loggers: Array[Logger]): Array[Task] =
-      props.map(_._1).toSet.toArray map { name =>
+    def execute(handler: EventHandler, loggers: Array[Logger]): Array[Task] = {
+      // If the task contains only `TestSelector`s, then run only these props instead of the whole suite.
+      val propFilter: String => Boolean =
+        if (td.selectors().forall(_.isInstanceOf[TestSelector]))
+          td.selectors().collect { case ts: TestSelector => ts.testName() }.toSet
+        else
+          Function.const(true)
+      props.map(_._1).toSet.filter(propFilter).toArray map { name =>
         checkPropTask(
           new TaskDef(
             td.fullyQualifiedName(),
@@ -102,6 +108,7 @@ private abstract class ScalaCheckRunner extends Runner {
             Array(new TestSelector(name))),
           single = true)
       }
+    }
   }
 
   def checkPropTask(taskDef: TaskDef, single: Boolean): BaseTask = new BaseTask(taskDef) { self =>