Use throw instead of exceptions for control flow

[ixti]

Is there an reason to not sue catch(...) { throw ... } instead of { begin; raise ...; rescue ...; end`?

[flash-gordon]

There is, it's even mentioned in the docs https://dry-rb.org/gems/dry-monads/1.3/do-notation/#transaction-safety Also see #98 (comment)

[ixti]

Oh, I missed that indeed. But I find rationale to be somewhat questionable - it's somewhat a side-effect that works ATM for some gems (AR and ROM). And IMHO it makes code less obvious.

Without do-notation one would write something like (pseudocode):

repo.transaction do |t|
  foo.bind { |v| bar.bind(v) }.or { t.rollback! }
end

So, I was expecting do-notation to provide me only fail-fast railroad. For transaction handling I would wrap my code separately:

repo.transaction do |t|
  method_with_do_notation.or { t.rollback! }
end

[flash-gordon]

You can have your own version of do notation in your code, nothing stops you from building one. When it comes to the gem I want safer defaults and, besides, my projects' code relies on the current behavior. I believe the same is true for other people since it's mentioned in the docs.

In summary, it's an intentional design choice, but you're right, using catch/throw would be equivalent to some extent.

[ixti]

Fair point.