From: "Gerard A.W. Vreeswijk" <gv@...>
Date: 2003-07-07T17:15:45+09:00
Subject: trapping compile time errors

Hi,

I want to catch compile time errors with my own method.

In Perl, you can do this:

   $SIG{__DIE__} = \&die;

   sub die {
      print "Error here.  May be any error, including SyntaxError\n";
      exit 1;
   }

I.e., you can trap die and define your own.  Does anyone know how to do
this in Ruby?  I have tried opening up Exception class and redefining
some of the methods there.  No success.  Eventually,
I came up with the following, which is not as I imagined.  It's ugly.
I am sure there exist better ways but currently I ran out of ideas.
Does anyone have better ideas?  Thanks.

===============================================================
#!/usr/bin/ruby
begin
   # From Pickaxe book:
   # eval( aString [, aBinding [ file [ line ] ] ]) -> anObject
   # Evaluates the Ruby expression(s) in aString. If aBinding is
   # given, the evaluation is performed in its context. The
   # binding may be a Binding object or a Proc object. If the
   # optional file and line parameters are present, they will
   # be used when reporting syntax errors.
   eval DATA.gets(nil), nil, __FILE__, DATA.lineno
   # gets(nil), because we want to set the line separator to be
   # nil so that entire DATA is slurped into one big string.
rescue Exception
   puts "Error here.  May be any error, including SyntaxError"
   # Redirect STDERR to STDOUT
   STDERR.reopen(STDOUT)
   # re-raise error.  Now appears on STDOUT
   raise
end
__END__
# Your program here, including possible syntax errors.
%&^&$%


===============================================================
Outputs:
Error here.  May be any error, including SyntaxError
try.rb:13: compile error (SyntaxError)
try.rb:13: parse error
%&^&$%
     ^
>Exit code: 1    Time: 0.229
===============================================================