VERSION constant issue

Ruby
1

Ruby’s VERSION constant is getting in the way of using #const_missing
in my module. Here’s some example code:

module Foo
def self.const_data
@const_data ||= { ‘version’ => ‘1.0.0’ }
end

def self.const_missing(name)
  key = name.to_s.downcase
  const_data[key] || super(name)
end

end

Foo::VERSION #=> ‘1.8.7’

How can I fix this?

I tried remove_const(:VERSION) at the toplevel but discovered that
some Ruby library don’t like that (sorry, can’t recall which it was
off hand).

2

On Thu, Nov 25, 2010 at 2:54 PM, Intransition [email protected]
wrote:

const_data[key] || super(name)
end
end

Foo::VERSION #=> ‘1.8.7’

How can I fix this?

I tried remove_const(:VERSION) at the toplevel but discovered that
some Ruby library don’t like that (sorry, can’t recall which it was
off hand).

Is this really an issue with ::VERSION? To me this rather looks like
an issue with lookup logic (either the general or yours) since the
same would apply to all other constants, wouldn’t it?

Kind regards

robert

3

hrm…

cfp:~ > cat a.rb
module Lib
def Lib.const_data
@const_data ||= {
‘version’ => ‘4.2.0’
}
end

def Lib.const_missing(const)
const_data[const.to_s.downcase] || super
end
end

p Lib::VERSION

cfp:~ > rvm a.rb

info: ruby-1.8.7-p302: ruby 1.8.7 (2010-08-16 patchlevel 302) [i686- darwin9.8.0]

“4.2.0”

info: ruby-1.9.2-p0: ruby 1.9.2p0 (2010-08-18 revision 29036) [i386- darwin9.8.0]

“4.2.0”

4

On Nov 25, 12:54pm, Josh C. [email protected] wrote:

key = name.to_s.downcase
off hand).
const_data[key] || super(name)

going back through ruby versions

I wasn’t able to get these to print

the ruby version until 1.7.1

thanks, ruby-versions.net :slight_smile:

Foo::VERSION # => “1.0.0”
Foo::VERSION # => “1.0.0”

Hmmm… I haven’t been able to quite get the rhyme or reason of the
behavior, but I just got the error again. The code is:

class TracePoint

# Access to metadata.
def self.metadata
  @metadata ||= (
    require 'yaml'
    YAML.load(File.new(File.dirname(__FILE__) + '/

tracepoint.yml’))
)
end

# Access metadata as constants.
def self.const_missing(name)
  name = name.to_s
  metadata[name] || super(name)
end

When I use run:

require ‘tracepoint’
TracePoint::VERSION

I get:

tryit.rb:2: warning: toplevel constant VERSION referenced by
TracePoint::VERSION
“1.8.7”

I got this on both:
ruby 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]
ruby 1.8.7 (2010-08-16 patchlevel 302) [x86_64-linux]

Ruby 1.9.2 is not a problem.

5

On Thu, Nov 25, 2010 at 7:54 AM, Intransition [email protected]
wrote:

 const_data[key] || super(name)

Here are my results.

module Foo
def self.const_data
@const_data ||= { ‘version’ => ‘1.0.0’ }
end

def self.const_missing(name)
key = name.to_s.downcase
const_data[key] || super(name)
end

VERSION # => “1.8.7”
self::VERSION # => “1.0.0”

def self.method
VERSION # => “1.8.7”
end
method
end

going back through ruby versions

I wasn’t able to get these to print

the ruby version until 1.7.1

thanks, ruby-versions.net :slight_smile:

Foo::VERSION # => “1.0.0”
Foo::VERSION # => “1.0.0”

6

On Nov 25, 2010, at 05:54, Intransition wrote:

 const_data[key] || super(name)

end
end

Foo::VERSION #=> ‘1.8.7’

How can I fix this?

What would ::const_data provide that Module#constants, Module#const_get
and Module#const_set and direct constant access don’t provide? If it’s
something legitimate, invert ::const_data to reference real constants
via introspection and get rid of const_missing.

I tried remove_const(:VERSION) at the toplevel but discovered that
some Ruby library don’t like that (sorry, can’t recall which it was
off hand).

File a bug, they should be using RUBY_VERSION.

7

On Nov 25, 9:03am, Robert K. [email protected] wrote:

Is this really an issue with ::VERSION? To me this rather looks like
an issue with lookup logic (either the general or yours) since the
same would apply to all other constants, wouldn’t it?

Yes, it would be.

8

On Dec 13, 1:21pm, Eric H. [email protected] wrote:

def self.const_missing(name)
key = name.to_s.downcase
const_data[key] || super(name)
end
end

Foo::VERSION #=> ‘1.8.7’

How can I fix this?

What would ::const_data provide that Module#constants, Module#const_get and
Module#const_set and direct constant access don’t provide? If it’s something
legitimate, invert ::const_data to reference real constants via introspection and
get rid of const_missing.

I could, but I wanted to lazy load the information b/c it is being
read from a file, and in most usecases will not be used. The reason I
am using constants is simply b/c it’s customary in this case as the
information is project metadata, such as VERSION.

I tried remove_const(:VERSION) at the toplevel but discovered that
some Ruby library don’t like that (sorry, can’t recall which it was
off hand).

File a bug, they should be using RUBY_VERSION.

Will do. I tracked it down to a Ruby 1.8.7:

e2mmap.rb:fail “Use Ruby 1.1” if VERSION < “1.1”