[ruby-core:93287] [Ruby trunk Feature#15936] on_error in lieu of rescue, raise

Issue #15936 has been updated by kylemacey (Kyle Macey).


duerst (Martin Dst) wrote:
> kylemacey (Kyle Macey) wrote:
> 
> > This is coming from a need that I personally face often on the utilities I work on, where I need to update state on an object if something unexpected happens. My company's linter gets upset when I use the `rescue StandardError` pattern, so I was hoping to have a way to be more explicit that I'm not trying to prevent the error from going up the stack, I just want to act upon the exception.
> 
> What about getting the linter to recognize that you are using `raise` again in the `rescue` clause? That shouldn't be too difficult, at least for the simple cases.

Very true! I can certainly do that, I just thought this might have the added benefit of writing more explicit and intentional code, and would eliminate the need to re-raise the exception.

----------------------------------------
Feature #15936: on_error in lieu of rescue, raise
https://bugs.ruby-lang.org/issues/15936#change-78755

* Author: kylemacey (Kyle Macey)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
A common bad pattern in ruby is to rescue any exception and accidentally clobber the exception. 

```
begin
  some_method
rescue StandardError
  # 
end
```

Most linters will complain if you write rescues like the code above. However, this could be useful if we want to perform an operation on _any_ error, as long as we re-raise the exception after doing our work.

```
begin
  some_method
rescue StandardError
  job.fail! 
  raise
end
```

Here, though, we run the risk of potentially forgetting to reraise the exception, or having to make exceptions in our linter for an operation that is overall benign.

What would be a thought on using another keyword that doesn't actually _rescue_ an exception, but performs an operation in the event of an error? Similar to `ensure`, but only in the event of an error.

```
begin
  some_method
on_error StandardError
  job.fail! 
end
```

(obviously, someone more creative than me should come up with a better name)



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