[Proposal] More intuitive import shadowing

[Krzysztof Wende]

Right now when we import a module A

defmodule CurrentA do
  def public1, do: 1
  def public2, do: 2
  def public3, do: 3
end


defmodule CurrentA do
  import CurrentA, only: [public1: 0]
  import CurrentA
 
  def test, do: public2() # No problem whatsoever
end

But whenever we add `except` to it

defmodule CurrentA do
  def public1, do: 1
  def public2, do: 2
  def public3, do: 3
end


defmodule CurrentA do
  import CurrentA, only: [public1: 0]
  import CurrentA, except: [public3: 0]
 
  def test, do: public2() # undefined function public2/0
end

We get an error of inexistent function. For me it feels super counter-intuitive.

Thoughts?
Cheers,
Krzysztof

[Ben Wilson]

Setting aside whether or not the existing functionality is intuitive or not, this isn't actually a proposal. You aren't suggesting an alternative.

[José Valim]

This is also by design and mentioned in the docs. Except is always exclusive on a previously defined import, if there is no import, then we take all macros and functions.

Imagine you "import Foo.Bar, only: ..." and then in some part of your code you have a conflict and would you like to remove that conflict in particular. If except brought everything back, it would be confusing behaviour and the only alternative would be for you to repeat the whole list in :only except for the element you want removed.

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

--
You received this message because you are subscribed to the Google Groups "elixir-lang-core" group.
To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/7f1e33c3-21d4-4c0f-b176-bdcc1fe35f81%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Krzysztof Wende]

Ok, 

But now let's imagine this scenario:

defmodule MyHelper do
  defmacro __using__(_) do
    quote do
      import List, only: [foldl: 3]
    end
  end

end
defmodule A do
  use MyHelper
  import List, except: [zip: 1]
 
  def test, do: foldr([1,2,3], 10, &(&1 + &2))
end

We'd obviosly expect in module A to have all of the List functions except zip, but we actually get none except for foldl.

[José Valim]

You can still undo it by bringing all of List and then using except. So you have an option to bring it all in once again. If it behaved like you proposed, then it would be impossible to filter without fully repeating the previous declaration.

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

--
You received this message because you are subscribed to the Google Groups "elixir-lang-core" group.
To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscribe@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/c66685df-3382-41a6-9c41-50959a72c205%40googlegroups.com.