From: Robert Klemme <shortcutter@...>
Date: 2011-11-29T22:56:28+09:00
Subject: Re: Loading a faulty ruby file - forcing this

On Tue, Nov 29, 2011 at 11:38 AM, Marc Heiler <shevegen@linuxmail.org> wrote:
> Hi.
>
> Consider you have two ruby files.
>
> file1.rb:
> ---------------------------------------------------
> require 'pp'
> RUBY_FILE = './file2.rb'
>
> begin
>  load RUBY_FILE
> rescue NameError => error
>  # pp error # Do not report the error here. Be silent.
> end
>
> # Now we call the two methods defined in file2.rb
> foo()
> bar()
> ---------------------------------------------------
>
> file2.rb:
> ---------------------------------------------------
>
> def foo
>  puts 'This is from foo()'
> end
>
> # Create an error on purpose here.
> joe_doe()
>
> def bar # The second method.
>  puts 'This is from bar()'
> end
> ---------------------------------------------------
>
> Note - I use the parens () at bar() to make it more
> explicit and illustrate my question.
>
> If you run file1.rb, an error occurs:
>
> undefined method `bar' for main:Object (NoMethodError)
>
>
> The method call to foo() works.
>
> If you look at the content of file2.rb, you can see that
> the method definition first has foo(), then a method
> call to a method that does not exist (on purpose), and
> then the method definition to bar()
>
> Ruby apparently stops processing file2.rb when it
> encounters a NameError exception.

Of course.  An exception always immediately stops execution at the
point where it is thrown and unwinds the stack until it finds a
handler (or the process terminates).

> My question is:
>
> - Is there a way to force or otherwise cause Ruby to continue
> reading the second file? I am in control of the ruby files so
> I can use eval without a problem.

Basically you could wrap every individual section with "begin rescue
end".  Then such a section would be the smallest part which could
fail.  Alternatively you could split the file in multiple parts and
have a specific implementation of "load" which ignores errors:

def load_ignorant(s)
  load(s)
rescue Exception
    # eat it
end

> What I would like to achieve is to let ruby read a file
> and treat it as a ruby file, but if it encounters errors,
> it would disregard these errors, and continue processing
> them.
>
> In a way, I'd need a faulty ruby loader that ignores errors
> when instructed.
>
> Right now, in the code above, I can not achieve this, as
> ruby stops the very moment it encounters an invalid method
> call. How could I continue to process that faulty file?

Why do you want to do that?  That sounds like a bad plan to me since
you won't notice any issues and your application's state is unclear.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/