Faster and simpler Java 9 classpath implementation

  - Take advantage of the `/packages` index provided by the
    jrt file system to avoid (expensive) Files.exist for
    non-existent entries across the full list of modules.
  - Extends ClassPath directly which leads to a simpler
    implemnentation that using the base class.
  - Add a unit test that shows we can read classes and packages
    from the Java standard library.

Fixes scala/scala-dev#306

With this change bootstrap time under Java 9 was comparable to
Java 8. Before, it was about 40% slower.

1 files changed, 41 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/classpath/JrtClassPathTest.scala b/test/junit/scala/tools/nsc/classpath/JrtClassPathTest.scala
new file mode 100644
index 0000000000..2c3c5134da
--- /dev/null
+++ b/test/junit/scala/tools/nsc/classpath/JrtClassPathTest.scala
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import org.junit.Assert._
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+import scala.tools.nsc.Settings
+import scala.tools.nsc.backend.jvm.AsmUtils
+import scala.tools.nsc.util.ClassPath
+import scala.tools.util.PathResolver
+
+@RunWith(classOf[JUnit4])
+class JrtClassPathTest {
+
+  @Test def lookupJavaClasses(): Unit = {
+    val specVersion = scala.util.Properties.javaSpecVersion
+    // Run the test using the JDK8 or 9 provider for rt.jar depending on the platform the test is running on.
+    val cp: ClassPath =
+      if (specVersion == "" || specVersion == "1.8") {
+        val settings = new Settings()
+        val resolver = new PathResolver(settings)
+        val elements = new ClassPathFactory(settings).classesInPath(resolver.Calculated.javaBootClassPath)
+        AggregateClassPath(elements)
+      }
+      else JrtClassPath().get
+
+    assertEquals(Nil, cp.classes(""))
+    assertTrue(cp.packages("java").toString, cp.packages("java").exists(_.name == "java.lang"))
+    assertTrue(cp.classes("java.lang").exists(_.name == "Object"))
+    val jl_Object = cp.classes("java.lang").find(_.name == "Object").get
+    assertEquals("java/lang/Object", AsmUtils.classFromBytes(jl_Object.file.toByteArray).name)
+    assertTrue(cp.list("java.lang").packages.exists(_.name == "java.lang.annotation"))
+    assertTrue(cp.list("java.lang").classesAndSources.exists(_.name == "Object"))
+    assertTrue(cp.findClass("java.lang.Object").isDefined)
+    assertTrue(cp.findClassFile("java.lang.Object").isDefined)
+  }
+}