From: "matz (Yukihiro Matsumoto)" <noreply@...>
Date: 2021-10-21T06:28:16+00:00
Subject: [ruby-core:105716] [Ruby master Feature#18083] Capture error in ensure block.

Issue #18083 has been updated by matz (Yukihiro Matsumoto).


First, I am not going to change the syntax for the `ensure` clause. The `ensure` clause is to unwind-protect so it is not recommended to branch depending on exceptions.

I admit the current `$!` behavior is error-prone. But considering compatibility, I am not sure we can fix the problem. For the workaround at the moment, avoid using `$!`. If it is possible to address the issue (e.g. @ko1's proposal of dynamic scoping or giving a warning for the bad usage), I agree with experimenting with them.

Matz.


----------------------------------------
Feature #18083: Capture error in ensure block.
https://bugs.ruby-lang.org/issues/18083#change-94214

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
As discussed in https://bugs.ruby-lang.org/issues/15567 there are some tricky edge cases.

As a general model, something like the following would be incredibly useful:

``` ruby
begin
 ...
ensure => error
  pp "error occurred" if error
end
```

Currently you can get similar behaviour like this:

``` ruby
begin
  ...
rescue Exception => error
  raise
ensure
  pp "error occurred" if error
end
```

The limitation of this approach is it only works if you don't need any other `rescue` clause. Otherwise, it may not work as expected or require extra care. Also, Rubocop will complain about it.

Using `$!` can be buggy if you call some method from `rescue` or `ensure` clause, since it would be set already. It was discussed extensively in https://bugs.ruby-lang.org/issues/15567 if you want more details.



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>