From: "JustJosh (Joshua Stowers) via ruby-core" <ruby-core@...>
Date: 2025-02-27T17:05:50+00:00
Subject: [ruby-core:121200] [Ruby master Feature#21160] Local return from proc

Issue #21160 has been updated by JustJosh (Joshua Stowers).


nobu (Nobuyoshi Nakada) wrote in #note-3:
> Why not rescue `LocalJumpError`?

That is definitely a better solution than requiring developers to use `next`.
Thank you for the suggestion.

As I understand it, the reason `break` doesn't work in my example is because the proc is "orphaned."
Ref: https://docs.ruby-lang.org/en/3.3/Proc.html#class-Proc-label-Orphaned+Proc
If an orphan-friendly implementation or alternative to `break` is worth considering, I would be happy to take a shot.


----------------------------------------
Feature #21160: Local return from proc
https://bugs.ruby-lang.org/issues/21160#change-112138

* Author: JustJosh (Joshua Stowers)
* Status: Open
----------------------------------------
When writing DSL-style helper methods, I often store block arguments as procs to use as callbacks.
Using `return` in a proc will return from the context it was created in, which is unsuitable in the following example.
Since procs cannot be converted to lambdas, I end up using `next` to return a value from them early.

Example:
``` ruby
fulfills_promise :generate_large_image do |image_data|
  next false if image_data.nil?

  puts 'Saving image..'
  # etc.
end
```

This works but confuses most readers.

I propose introducing an alias for it that is more appropriate for this use case.
Perhaps `pass` or `continue`?

It's worth noting that `return` would work with `fulfills_promise :foo, -> (bar) do`, though it detracts a bit from a DSL's expressiveness.




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