From: Josh Cheek <josh.cheek@...>
Date: 2013-07-05T23:08:28+09:00
Subject: How do I rescue a program exception in an at_exit block?

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I was thinking about how bad I am at reading error messages, and realized
it could be useful to catch the exception and write it in a way that was
easier for me to find the relevant information. So, came up with this proof
of concept:

at_exit do
  error = $!
  if error
    pink, normal, red, green = "\e[35m", "\e[0m", "\e[31m", "\e[32m"

    puts
    puts "#{pink}#{error.class}"
    puts "#{red}#{error.message}#{normal}"
    puts
    puts error.backtrace.map { |line|
      line.sub(%r([^/:]*(?=:)))    { |match| "#{green}#{match}#{normal}" }
          .sub(%r((?<=:)\d+(?=:))) { |match| "#{pink}#{match}#{normal}" }
    }
  end
end


The problem, though, is that $! is still set after this block runs, and so
Ruby still spits out its own exception message afterwards. I don't know how
to stop it from doing this.

I tried setting $!, but it's a read-only variable. Tried raising and
rescuing another exception, which cleared $! for the rest of that at_exit
block, but it was still around in the next at_exit block, and so Ruby still
printed it out. Not sure what else to try.

-Josh

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<div>I was thinking about how bad I am at reading error messages, and reali=
zed it could be useful to catch the exception and write it in a way that wa=
s easier for me to find the relevant information. So, came up with this pro=
of of concept:</div>
<div><br></div><div>at_exit do</div><div>=A0 error =3D $!</div><div>=A0 if =
error</div><div>=A0 =A0 pink, normal, red, green =3D &quot;\e[35m&quot;, &q=
uot;\e[0m&quot;, &quot;\e[31m&quot;, &quot;\e[32m&quot;</div><div><br></div=
><div>=A0 =A0 puts</div>
<div>=A0 =A0 puts &quot;#{pink}#{error.class}&quot;</div><div>=A0 =A0 puts =
&quot;#{red}#{error.message}#{normal}&quot;</div><div>=A0 =A0 puts</div><di=
v>=A0 =A0 puts error.backtrace.map { |line|</div><div>=A0 =A0 =A0 line.sub(=
%r([^/:]*(?=3D:))) =A0 =A0{ |match| &quot;#{green}#{match}#{normal}&quot; }=
</div>
<div>=A0 =A0 =A0 =A0 =A0 .sub(%r((?&lt;=3D:)\d+(?=3D:))) { |match| &quot;#{=
pink}#{match}#{normal}&quot; }</div><div>=A0 =A0 }</div><div>=A0 end</div><=
div>end</div><div><br></div><div><br></div><div>The problem, though, is tha=
t $! is still set after this block runs, and so Ruby still spits out its ow=
n exception message afterwards. I don&#39;t know how to stop it from doing =
this.</div>
<div><br></div><div>I tried setting $!, but it&#39;s a read-only variable. =
Tried raising and rescuing another exception, which cleared $! for the rest=
 of that at_exit block, but it was still around in the next at_exit block, =
and so Ruby still printed it out. Not sure what else to try.</div>
<div><br></div><div>-Josh</div>

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