Suggestion : No rescue without class

[coding-red-panda]

Hello,

just a small suggestion.
Would it be possible to create a cop that checks rescue statements and if they are actually catching a specific error?

This would be accepted:

def some_function
  begin
    do_something
  rescue StandardError => e
    do_something_else
  end
end

def some_function
  do_something
rescue StandardError => e
  do_something_else
end

And these 2 examples would not be accepted anymore:

def some_function
  begin
    do_something
  rescue
    do_something_else
  end
end

def some_function
  do_something
rescue
  do_something_else
end

It's kinda a policy we have in our team that specific errors should be caught and not just every globbed up.

[alexdowad]

We already have something like this. Lint/RescueException flags rescue Exception, since it "swallows" all exceptions.

[coding-red-panda]

does that cover simply writing rescue without a class? cause just rescue defaults to StandardError

[alexdowad]

Maintainers, do we want something like this? There are a lot of Ruby codebases which use idioms like:

a = Integer(str) rescue nil

[bbatsov]

@alexdowad I think we have a cop that checks for this very same thing. :-) I think RescueException can be extended to handle @NekoNova's case as this is more or less the same thing.

[HParker]

I looked into this briefly. From what I found the RescueException cop is there to prevent catching exceptions that you maybe shouldn't be catching. The suggestion in this issue is that rescue blocks should communicate more about what type of exception they are trying to catch.

To me that sounds like a different cop. Does that sound right to others as well?

[jonas054]

@HParker That sounds right. The message from Lint/RescueException is "Avoid rescuing the Exception class. Perhaps you meant to rescue StandardError?". Reporting where StandardError is caught without being explicitly named is a different issue. So, a new cop.

[Drenmi]

@HParker: Agree with both of you on that. 😀

[olegantonyan]

Why rescue StandardError is ok, but just rescue is not if these two are the same? I would expect either rescue StandardError the same offense, or not to consider rescue without class an offense at all. It's just a syntactic sugar in Ruby.

[coding-red-panda]

it's about being explicit and forcing people to think about what they want to rescue instead of gobbling up all errors.
If you catch an exception, you should handle it and do something with it, not just gobble it up.

That was the main idea behind my feature request for this.

[Drenmi]

The difference is saying "I'm deliberately rescuing StandardError, just so you know" vs. saying "I might have no idea what I'm rescuing, or I might, you figure it out." 🙂