From: Joel VanderWerf <vjoel@...>
Date: 2005-12-18T06:12:44+09:00
Subject: Re: Rescuing SyntaxError

Caleb Tennis wrote:
> Is it possible to catch illegal syntax errors?
> 
> 
> irb(main):001:0> 550p
> SyntaxError: compile error
> 
> ...
> 
> # se.rb
> begin
>   550p
> rescue SyntaxError => e
>   # This never seems to get run
>   puts "Caught a syntax error: " + e
> end
> 
> ~> ruby se.rb
> blah.rb:2: syntax error
> 
> Thanks,
> Caleb

[~/tmp] cat se2.rb
begin
  eval <<-END
    begin
      550p
    rescue SyntaxError => e
      # This never seems to get run
      puts "Caught a syntax error: " + e
    end
  END
rescue SyntaxError
  puts "Caught a syntax error during eval"
end
[~/tmp] ruby se2.rb
Caught a syntax error during eval


The reason the inner rescue is not triggered is that the exception
occurs while eval is turning the string into a parse tree, before it
starts executing the parse tree.

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407