Error handling - help please?

[swaldman]

Does anybody have time to do a quick rundown on how error handling should be done in DW, going forward?

There are a number of different ways of doing things within the codebase at present. I've tended to adopt LJ::throw for new stuff because it seemed comprehensible(!), but Mark has recently said in a review "I... don't think we use LJ::Error anywhere useful anymore. It's pretty old.". (given where the comment was made I assume that it referred to a LJ::throw statement, which I imagine must be part of a LJ::Error package)

So I'm wondering what best practice is now, and thus what we should do in new code?

Thanks

Comments

[mark]

I was actually contemplating this after your reply to my code review comment.

Of late, I've just been using Carp's croak/confess or die (as appropriate). I think that exceptions (using Try::Tiny or similar) is just... a lot of effort for relatively little gain, when you can do similar with eval if you really want.

I would suggest that you do one of two things:

1) If you want to die from the perspective of the caller, use Carp's "croak". If you want to die with a backtrace, use "confess".

2) If you want to die from YOUR perspective, use "die".

Why would you pick one or the other? Think about it like this... the error message will include your message plus a file name and line number. What would be more useful -- seeing "MyModule.pm line 85" or seeing "whoever called me line 395"?

If it's the former, die. If the latter, use Carp.

Generally, the latter is probably correct -- since you want to say that the call to your method failed, and here's the reason why. Instead of saying that something in your method failed.

All of this is much easier than LJ::throw and dealing with error objects, which are a fancy way of propagating information -- but all we really need in 99% of situations is what was the failure, what failed, and where.

Does that all make sense?