Feature #10320: require into module

• Status: Open
• Priority: Normal
• Assignee: -
• Target version: -

[sowieso (So Wieso)]

When requiring a library, global namespace always gets polluted, at least with one module name. So when requiring a gem with many dependencies, at least one constant enters global namespace per dependency, which can easily get out of hand (especially when gems are not enclosed in a module).

Would it be possible to extend require (and load, require_relative) to put all content into a custom module and not into global namespace?

Syntax ideas:

require 'libfile', into: :Lib   # keyword-argument
require 'libfile' in Lib   # with keyword, also defining a module Lib at current binding (unless defined? Lib)
require_qualified 'libfile', :Lib

This would also make including code into libraries much easier, as it is well scoped.

module MyGem
  require 'needed' in Need

  def do_something
    Need::important.process!
  end
end
 # library user is never concerned over needed's content

Some problems to discuss:

• requiring into two different modules means loading the file twice?
• monkeypatching libraries should only affect the module ­→ auto refinements?
• maybe also allow a binding as argument, not only a module?
• privately require, so that required constants and methods are not accessible from the outside of a module (seems to difficult)
• what about $global constants, read them from global scope but copy-write them only to local scope?

Similar issue:
https://bugs.ruby-lang.org/issues/5643

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

So Wieso wrote:

require 'libfile', into: :Lib   # keyword-argument
require 'libfile' in Lib   # with keyword, also defining a module Lib at current binding (unless defined? Lib)
require_qualified 'libfile', :Lib

Why the first and the last use a symbol?
The second will be difficult as require is not a reserved word but a mere method call.

• maybe also allow a binding as argument, not only a module?

Does it make sense?

[nobu (Nobuyoshi Nakada)]

• Related to Feature #5643: require/load options and binding option added

[sowieso (So Wieso)]

I chose the symbol :Lib, as I thought Ruby would complain if the constant Lib would not exist at this time. The keyword in would define it, if it would not exist. I would prefer if we could solve it without using symbols, but writing module Lib; end before the first require doesn't look nice.

Sorry, I didn't consider that require is a method, so I guess the keyword option (in) doesn't fit.
( Alternatively we could define suffix in as enclosing the given module:

require 'file' in Lib
# is equivalent
module Lib
  require 'file'
end

but then require has to check for its nesting.
)

[mikegee (Michael Gee)]

So Wieso wrote:

require 'file' in Lib
# is equivalent
module Lib
  require 'file'
end

I don't like changing require with one argument to mean something else. It would break too much legacy code.

If you want to require a feature into your current namespace how about this:

module Lib
  require 'lib', in: self
end

[nobu (Nobuyoshi Nakada)]

So Wieso wrote:

I chose the symbol :Lib, as I thought Ruby would complain if the constant Lib would not exist at this time. The keyword in would define it, if it would not exist. I would prefer if we could solve it without using symbols, but writing module Lib; end before the first require doesn't look nice.

It's ambiguous if Lib is a module or a class, when only the name is provided.

[sowieso (So Wieso)]

Michael Gee wrote:

I don't like changing require with one argument to mean something else. It would break too much legacy code.

You are definitely right here, we should not do that.

Nobuyoshi Nakada wrote:

It's ambiguous if Lib is a module or a class, when only the name is provided.

Is it? If the constant is already defined, take it (class or module). If not create a new module by this name.

[nobu (Nobuyoshi Nakada)]

So Wieso wrote:

Nobuyoshi Nakada wrote:

It's ambiguous if Lib is a module or a class, when only the name is provided.

Is it? If the constant is already defined, take it (class or module). If not create a new module by this name.

If you don't want to create a module by that name, you don't need to use the name.
Should not introduce implicit conversion between a name and a module.
You can use anonymous module too if is is a module object.

I think this feature should be an instance method of Module, similar to load rather than require.

[jwmittag (Jörg W Mittag)]

Nobuyoshi Nakada wrote:

I think this feature should be an instance method of Module, similar to load rather than require.

Yes, I believe having Module#load and possibly Module#require and Module#require_relative would be the most logical:

# not namespaced:
require 'foo'
module Bar;end

# namespaced:
module Bar
  require 'foo'
end

Re-using those names would be a backwards-incompatible change, though. I have seen people use the second form sometimes.

This is a replacement for the hard-to-use wrap optional argument to Kernel#load:

load 'foo', true

# is almost equivalent to 

Module.new.load 'foo'

This can be naturally extended to Binding#load, Binding#require, and Binding#require_relative.

As with the wrap argument to Kernel#load, the question is, what should references like ::String in the loaded script refer to? I think it would be nice if it offered complete isolation by default, with an option to revert to the current behavior of load, e.g. with an API like this:

class Module
  def load(path, pollute_global: false)
  end
end

[hsbt (Hiroshi SHIBATA)]

• Related to Feature #13847: Gem activated problem for default gems added