LostKobrakai
How to best format exceptions
I’m in the process of working on a library, where I want to have quite expressive exceptions (due to a lot of domain specific constraints). I’m wondering if there any guidelines of how to best format those though?
There are questions like:
-
Are multi line exceptions generally fine?
-
When to start using blame if the stacktrace or expensive operations are not needed?
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Is it generally ok to add ANSI escape sequences for formatting, or would this cause issues?
I noticed that e.g. the FunctionClauseError exception doesn’t add ANSI sequences by itself, but it’s special cased within IEx to add some proper coloring, while for other exceptions there’s a check for a reset sequence in the exception string.
First Post!
dimitarvp
What do you mean by expressive exceptions? Is there any required format, or in general, a bucket list of requirements?
To me multi-line exceptions are always fine; you either need a stack trace or sometimes the error message cannot be super short. Both things shouldn’t ever be a deal-breaker when constructing exceptions / errors.
Another example: when showing errors in tests I love the “expected X, got Y” format.
I am definitely not an authority on anything (it’s questionable if I’ll be working commercial programming 10 years from now even) but I have found the following format successful when I was working on and with huge Java monstrosities a lifetime ago:
Action: Saving config to ~/.config/my_program/my_program.toml
Error: Access denied
Suggestion: Change the permission flags of the file.
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