Constant lookup as-if toplevel

Ruby
1

I’m evaluating a ruby script against a testing DSL that I wrote. Now I
would have loved to run the scripts at the toplevel, but the
contamination of the Object class makes that infeasible. So I run them
within a Scope object. Basically:

class Scope < Module

def initialize
  extend self
end

def execute(script, filename)
  eval(script, binding, filename)
end

end

My problem arises when a script uses a constant that isn’t defined and
the error message looks like this:

ERROR: NameError uninitialized constant #Scope:0x7f3cc21e5630::Foo

I’m trying to find a way to get rid of the #<Scope:...>:: part. To
the end user it should at least look like things are running at
toplevel.

I tried adding to Scope:

def inspect; “”; end

But that did not work. Any ideas?

2

I ran into this same problem today myself, although attempting something
different. I wanted to stylize a constant name with a bang! Our
company’s
name happens to be stylized with a bang, so I thought I’d be silly and
try
to translate that into Ruby itself (I was inspired by Rainbows!)

So I tried this:

http://gist.github.com/653850Which is fine, but when I created classes
within the namespace of my bangmodule, they still inspect without the
bang!

I want the bang! Bring on the bang!

3

Why not add a const_missing() to your Scope class and explicitly lookup
the constant on Object there, which will fail, and so the error will be
as if a top-level constant wasn’t found:

class Scope
def const_missing(const)
Object.const_get(const)
end
end

test:

class Scope
Hello
end

#=> NameError: uninitialized constant Hello

Also, why don’t you run the script like follows:

load "myscript.rb", true

So that top-level is replaced by an anonymous module. This should
obviate the need for your Scope hack, i think.

4

err, that should be:

class Scope
  def self.const_missing(const)
    Object.const_get(const)
  end
end

John

5

On Sat, Oct 30, 2010 at 12:06 AM, Intransition [email protected]
wrote:

yup

def execute( script, filename )
eval(script, Module.new.send(:binding), filename)
end
execute( “Foo”, “here” )

which gives

here:1:in `execute’: uninitialized constant Object::Foo (NameError)

does this suit your needs better?
If this still causes the conflicts you were talking about, I like John’s
idea.

HTH
R

6

On Oct 31, 12:28am, John M. [email protected] wrote:

err, that should be:

class Scope
def self.const_missing(const)
Object.const_get(const)
end
end

Nice. I removed self. b/c Scope is a self extended module, and it
looks good.

Thanks.