Thread#raise should call #exception in the target thread

* This is needed by Timeout.timeout in ruby/timeout#15
* Reuse Kernel#raise for convenience to both
  call #build_exception_for_raise and set the backtrace and print if $DEBUG.

Author: eregon

CHANGELOG.md

@@ -27,6 +27,7 @@ Compatibility:
 * Fix `Float#/` when dividing by `Rational` (@bjfish).
 * `Process.euid=` should accept String (#2615, @ngtban).
 * Fix `instance_variable_get` and `instance_variable_set` for immutable objects (@bjfish).
+* `Thread#raise(exc, message)` now calls `exc.exception` in the target thread like CRuby (@eregon).
 
 Performance:
 

spec/ruby/core/thread/raise_spec.rb

@@ -102,6 +102,30 @@
       raised_again.backtrace.first.should_not include("#{__FILE__}:#{raise_again_line}:")
     end
   end
+
+  it "calls #exception in both the caller and in the target thread" do
+    cls = Class.new(Exception) do
+      attr_accessor :log
+      def initialize(*args)
+        @log = [] # This is shared because the super #exception uses a shallow clone
+        super
+      end
+
+      def exception(*args)
+        @log << [self, Thread.current, args]
+        super
+      end
+    end
+    exc = cls.new
+
+    @thr.raise exc, "Thread#raise #exception spec"
+    @thr.join
+    ScratchPad.recorded.should.is_a?(cls)
+    exc.log.should == [
+      [exc, Thread.current, ["Thread#raise #exception spec"]],
+      [ScratchPad.recorded, @thr, []]
+    ]
+  end
 end
 
 describe "Thread#raise on a running thread" do

src/main/java/org/truffleruby/core/thread/ThreadManager.java

@@ -376,7 +376,6 @@ private void setException(RubyThread thread, RubyException exception, Node curre
 
             if (!isSystemExit && thread.reportOnException) {
                 final TruffleSafepoint safepoint = TruffleSafepoint.getCurrent();
-
                 boolean sideEffects = safepoint.setAllowSideEffects(false);
                 try {
                     DispatchNode.getUncached().call(context.getCoreLibrary().truffleThreadOperationsModule,

src/main/java/org/truffleruby/core/thread/ThreadNodes.java

@@ -858,11 +858,14 @@ public static void raiseInThread(RubyLanguage language, RubyContext context, Rub
                     new SafepointAction("Thread#raise", rubyThread, true, false) {
                         @Override
                         public void run(RubyThread rubyThread, Node currentNode) {
-                            if (exception.backtrace == null) {
-                                exception.backtrace = context.getCallStack().getBacktrace(currentNode);
+                            final TruffleSafepoint safepoint = TruffleSafepoint.getCurrent();
+                            boolean sideEffects = safepoint.setAllowSideEffects(false);
+                            try {
+                                RubyContext.send(currentNode, rubyThread, "raise", exception);
+                            } finally {
+                                safepoint.setAllowSideEffects(sideEffects);
                             }
-
-                            VMRaiseExceptionNode.reRaiseException(context, exception);
+                            throw CompilerDirectives.shouldNotReachHere("#raise did not throw?");
                         }
                     });
         }