SI-5254 running an empty scala script should succeed

The script runner made the assumption that "compilation succeeded"
implies "there is a Main class to run", but this can be wrong if the
script is empty (or only contains imports/comments).

The ScriptRunner now uses the ClassPath utility to check if there really
is a main class. If not, it doesn't try to run it and returns
peacefully. This also makes `scala -e ''` succeed.

1 files changed, 23 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/ScriptRunnerTest.scala b/test/junit/scala/tools/nsc/ScriptRunnerTest.scala
new file mode 100644
index 0000000000..9bae7a0487
--- /dev/null
+++ b/test/junit/scala/tools/nsc/ScriptRunnerTest.scala
@@ -0,0 +1,23 @@
+package scala.tools.nsc
+
+import org.junit.Assert._
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+@RunWith(classOf[JUnit4])
+class ScriptRunnerTest {
+  @Test
+  def testEmptyScriptSucceeds: Unit = {
+    val s = new GenericRunnerSettings(s => ())
+    s.nc.value = true
+    s.usejavacp.value = true
+
+    // scala -nc -e ''
+    assertTrue(ScriptRunner.runCommand(s, "", Nil))
+
+    // scala -nc -save -e ''
+    s.save.value = true
+    assertTrue(ScriptRunner.runCommand(s, "", Nil))
+  }
+}