[ruby-core:115990] [Ruby master Feature#20102] Introduce `Fiber#resuming?`

Issue #20102 has been updated by Eregon (Benoit Daloze). Could you make it `raise FiberError` if it's called on a Fiber of a different thread? Because that's always racy (i.e. it might have changed by the time `resuming?` returns) so it seems wrong to query that for a Fiber belonging to another thread. ---------------------------------------- Feature #20102: Introduce `Fiber#resuming?` https://bugs.ruby-lang.org/issues/20102#change-105955 * Author: ioquatix (Samuel Williams) * Status: Open * Priority: Normal * Assignee: ioquatix (Samuel Williams) ---------------------------------------- There are some tricky edge cases when using `Fibre#raise` and `Fiber#kill`, e.g. ```ruby fiber = nil killer = Fiber.new do fiber.raise("Stop") end fiber = Fiber.new do killer.resume end fiber.resume # 4:in `raise': attempt to raise a resuming fiber (FiberError) # 4:in `block in <main>' ``` Async has to deal with this edge case explicitly by rescuing the exception: https://github.com/socketry/async/blob/ffd019d9c1d547926a28fe8f36bf7bfe91d8… I'd like to avoid doing that and instead just ask "Can I kill/raise on this fiber right now?" which is determined by whether the fiber itself can be resumed or transferred to. To address this, I'd like to introduce `Fiber#resuming?`: ```c /* * call-seq: fiber.resumed? -> true or false * * Whether the fiber is currently resumed. */ VALUE rb_fiber_resuming_p(VALUE fiber_value) { struct rb_fiber_struct *fiber = fiber_ptr(fiber_value); if (FIBER_TERMINATED_P(fiber)) return RUBY_Qfalse; return RBOOL(fiber->resuming_fiber); } ``` See the PR: https://github.com/ruby/ruby/pull/9382 -- https://bugs.ruby-lang.org/