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Bug #17331

Updated by nevans (Nicholas Evans) over 3 years ago

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" "message", transfer: true 
 # => 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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