From 943ab6aeac25fb382a5e4e8c8f5ad1b6d0fb183d Mon Sep 17 00:00:00 2001
From: Knut Franke <Knut.Franke@gmx.de>
Date: Thu, 9 Oct 2014 01:03:42 +0200
Subject: [PATCH] Implement Fiber#raise

---
 cont.c                  | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 test/ruby/test_fiber.rb | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+)

diff --git a/cont.c b/cont.c
index 2ff2cbb..b52cd96 100644
--- a/cont.c
+++ b/cont.c
@@ -941,6 +941,8 @@ static VALUE
 make_passing_arg(int argc, const VALUE *argv)
 {
     switch (argc) {
+      case -1:
+	return argv[0];
       case 0:
 	return Qnil;
       case 1:
@@ -1559,6 +1561,49 @@ rb_fiber_m_resume(int argc, VALUE *argv, VALUE fib)
 
 /*
  *  call-seq:
+ *     fiber.raise(string)                         -> obj
+ *     fiber.raise(exception [, string [, array]]) -> obj
+ *
+ *  Assuming that <code>resume</code> was called before, raises an exception in
+ *  the fiber at the point at which the last <code>Fiber.yield</code> was
+ *  called. If the <code>Fiber.yield</code> occurs within a
+ *  <code>begin...end</code> block with a +rescue+ clause matching the
+ *  exception being raised, <code>fiber.raise</code> evaluates to the arguments
+ *  passed to the next <code>Fiber.yield</code> statement inside the fiber's
+ *  block or to the block value if it runs to completion without any
+ *  <code>Fiber.yield</code>. Otherwise, the exception is propagated to the
+ *  caller.
+ *
+ *  If the fiber either has never been resumed or is dead, raises FiberError.
+ *
+ *  With a single +String+ argument, raises a +RuntimeError+ with the string as
+ *  a message.  Otherwise, the first parameter should be the name of an
+ *  +Exception+ class (or an object that returns an +Exception+ object when
+ *  sent an +exception+ message). The optional second parameter sets the
+ *  message associated with the exception, and the third parameter is an array
+ *  of callback information.
+ */
+static VALUE
+rb_fiber_raise(int argc, VALUE *argv, VALUE fibval)
+{
+    VALUE exc;
+    rb_fiber_t *fib;
+    GetFiberPtr(fibval, fib);
+    switch(fib->status) {
+	case CREATED:
+	    rb_raise(rb_eFiberError, "Cannot raise exception in an unborn fiber."
+		    " You need to resume first.");
+	case RUNNING:
+	    exc = rb_make_exception(argc, argv);
+	    return rb_fiber_resume(fibval, -1, &exc);
+	case TERMINATED:
+	    rb_raise(rb_eFiberError, "Cannot raise exception in a dead fiber.");
+    }
+    return Qundef;
+}
+
+/*
+ *  call-seq:
  *     fiber.transfer(args, ...) -> obj
  *
  *  Transfer control to another fiber, resuming it from where it last
@@ -1678,6 +1723,7 @@ Init_Cont(void)
     rb_define_singleton_method(rb_cFiber, "yield", rb_fiber_s_yield, -1);
     rb_define_method(rb_cFiber, "initialize", rb_fiber_init, 0);
     rb_define_method(rb_cFiber, "resume", rb_fiber_m_resume, -1);
+    rb_define_method(rb_cFiber, "raise", rb_fiber_raise, -1);
 }
 
 RUBY_SYMBOL_EXPORT_BEGIN
diff --git a/test/ruby/test_fiber.rb b/test/ruby/test_fiber.rb
index ed071ac..d8bae1f 100644
--- a/test/ruby/test_fiber.rb
+++ b/test/ruby/test_fiber.rb
@@ -107,6 +107,15 @@ class TestFiber < Test::Unit::TestCase
       }
       fib.resume
     }
+    assert_raise(FiberError){
+      fib = Fiber.new{}
+      fib.raise "raise in unborn fiber"
+    }
+    assert_raise(FiberError){
+      fib = Fiber.new{}
+      fib.resume
+      fib.raise "raise in dead fiber"
+    }
   end
 
   def test_return
@@ -125,6 +134,37 @@ class TestFiber < Test::Unit::TestCase
     }
   end
 
+  def test_raise
+    assert_raise(ZeroDivisionError){
+      Fiber.new do
+        1/0
+      end.resume
+    }
+    assert_raise(RuntimeError){
+      fib = Fiber.new{ Fiber.yield }
+      fib.raise "raise and propagate"
+    }
+    assert_nothing_raised{
+      fib = Fiber.new do
+        begin
+          Fiber.yield
+        rescue
+        end
+      end
+      fib.resume
+      fib.raise "rescue in fiber"
+    }
+    fib = Fiber.new do
+      begin
+        Fiber.yield
+      rescue
+        Fiber.yield :ok
+      end
+    end
+    fib.resume
+    assert_equal(:ok, fib.raise)
+  end
+
   def test_transfer
     ary = []
     f2 = nil
-- 
1.9.1