From: eregontp@...
Date: 2020-11-20T19:08:08+00:00
Subject: [ruby-core:100989] [Ruby master Feature#17331] Let Fiber#raise work with transferring fibers

Issue #17331 has been updated by Eregon (Benoit Daloze).


This new alternative sounds good to me. I also commented on the PR.

----------------------------------------
Feature #17331: Let Fiber#raise work with transferring fibers
https://bugs.ruby-lang.org/issues/17331#change-88655

* Author: nevans (Nicholas Evans)
* Status: Open
* Priority: Normal
----------------------------------------
It would be useful to use `raise` on transferring fibers just as we can with yielding fibers.

I've added a `transfer` kwarg, so it is not automatic; the caller must know how to handle the fiber.  If you call a yielding fiber with `transfer: true` or a transferring fiber without `transfer: true`, a `FiberError` will be raised. Resuming fibers still raise a `FiberError`.

```ruby
yielding_fiber.raise "message"
# => resumes and raises from the last Fiber.yield

transferring_fiber.raise "message", transfer: true
# => transfers and raises from the last fiber.transfer

resuming_fiber.raise "message"
# => raises FiberError
```

Implementation: https://github.com/ruby/ruby/pull/3783


I also implemented a second version that implicitly and automatically selects `rb_fiber_transfer_kw` for transferring fibers and `rb_fiber_resume_kw` for yielding fibers. The implicit version also raises `FiberError` on resuming fibers.


```ruby
yielding_fiber.raise "message"
# => resumes and raises from the last Fiber.yield

transferring_fiber.raise "message"
# => transfers and raises from the last fiber.transfer

resuming_fiber.raise "message"
# => raises FiberError
```

Alternate implicit implementation: https://github.com/ruby/ruby/pull/3795

I slightly prefer the explicit version, but I'm okay with the implicit version.



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