Emit mixin forwarders for JUnit-annotated trait methods by default

JUnit 4 does not support default methods. For better user experience,
this commit makes the compiler generate mixin forwarders for inherited
trait methods that carry a JUnit annotation.

The -Yjunit-trait-methods-no-forwarders flag disables this behavior.

This supersedes the scala-js/scala-2.12-junit-mixin-plugin compiler
plugin.

2 files changed, 25 insertions, 0 deletions

diff --git a/test/files/run/junitForwarders/C_1.scala b/test/files/run/junitForwarders/C_1.scala
new file mode 100644
index 0000000000..2af2026a61
--- /dev/null
+++ b/test/files/run/junitForwarders/C_1.scala
@@ -0,0 +1,15 @@
+trait T {
+  @org.junit.Test def foo = 0
+}
+
+class C extends T
+
+object Test extends App {
+  def check(c: Class[_], e: String) = {
+    val s = c.getDeclaredMethods.sortBy(_.getName).map(m => s"${m.getName} - ${m.getDeclaredAnnotations.mkString(", ")}").mkString(";")
+    assert(s == e, s"found: $s\nexpected: $e")
+  }
+  check(classOf[C], "foo - @org.junit.Test()")
+  // TODO scala-dev#213: should `foo$` really carry the @Test annotation?
+  check(classOf[T], "$init$ - ;foo - @org.junit.Test();foo$ - @org.junit.Test()")
+}
diff --git a/test/files/run/junitForwarders/Test.java b/test/files/run/junitForwarders/Test.java
new file mode 100644
index 0000000000..57c4d5b544
--- /dev/null
+++ b/test/files/run/junitForwarders/Test.java
@@ -0,0 +1,10 @@
+package org.junit;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.METHOD})
+public @interface Test { }