#276 new
Jarl Friis

rescue clauses does not catch exceptions

Reported by Jarl Friis | January 13th, 2010 @ 12:38 AM

Many places in the code there are statements like this

rescue => e

A type must be specified so such clauses should at least be

rescue Exception => e

However I will recommend to be more specific on such rescue clauses

I ran into this problem when I was going from running cruisecontrolrb manually to running cruisecontrolrb in daemon mode.

I attach a patch for that specific problem. But the problem is bigger than that, see for example the output of

grep -r 'rescue =>' *


Comments and changes to this ticket

  • Jarl Friis

    Jarl Friis January 13th, 2010 @ 06:50 AM

    I appologise my newbieness.

    I now realise that

    rescue =>

    rescues all StandardErrors (which is even better than all Exceptions). However my patch is still relevant for solving the specific problem regarding no user friendly error when missing mongrel gem. Because if mongrel gem is not installed, a Gem::LoadError is raised which is not a StandardError, hence the patch.


  • Tony Spataro

    Tony Spataro March 1st, 2010 @ 08:56 AM

    Hi Jarl,

    I wouldn't apologize for your newbie0ness just yet. In fact, it's rather dangerous only to catch StandardError, because StandardError is a subclass of Exception and most application-defined exceptions do NOT inherit from StandardError, but rather from Exception.

    If one throws a string or other object, I believe Ruby automatically constructs an Exception from it, which is not caught by a "rescue => e" clause.

    "rescue => e" is a very common error in Ruby code, which has let to many mysterious non-caught exceptions in projects I've worked on. I advise everyone I work with to avoid it.

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